Selina Class 8 ICSE Solutions

Selina Concise Biology Class 8 ICSE Solutions – Ecosystems

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Selina Concise Biology Class 8 ICSE Solutions – Ecosystems

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 8 Biology Chapter 4 Ecosystems. You can download the Selina Concise Biology ICSE Solutions for Class 8 with Free PDF download option. Selina Publishers Concise Biology for Class 8 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

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Selina Concise ICSE Solutions for Class 8 Biology Chapter 4 Ecosystems

REVIEW QUESTIONS

Multiple Choice Questions:

1. Put a tick mark (✓) against the correct alternative in the following statements:

a. The term “ecosystem” is derived from the Greek word “Oikos” meaning.

  1. Body weight
  2. Food
  3. House
  4. Size

b. Rat in any food chain would occupy the position of

  1. Tertiary consumer
  2. Secondary consumer
  3. Primary consumer
  4. Producer

c. Evergreen broad-leaved trees are characteristic of

  1. Tropical rain forests
  2. Temperate deciduous forests
  3. Coniferous forests
  4. All of the above types of forests.

Short Answer Type:

1. Mention if the following statements are true (T) or false (F).
(a) Snakes are primary consumers (T/F)
(b) Some humans are strictly primary consumers & some others are of other types of consumers also (T/F)
(c) No ecosystem can survive without light (T/F)
(d) Cattle go to ponds for drinking water, so they are a constituent of pond ecosystem (T/F)

Answer:

(a) Snakes are primary consumers (F)
No the snakes are not primary consumers as snakes eat rats and frogs as these are primary consumers which eat plant products. As snakes eat the primary consumers so the snakes are secondary consumers.

(b) Some humans are strictly primary consumers and some others are of other types of consumers also (T)
It is true that humans are vegetarians and eat plants or plant products. So these humans are vegetariBut there are certain humans which eat the flesh or eggs of other animals. These are carnivores and humans living plants are called Herbivores.

(c) No ecosystem can survive without light (T)
The plants and animals and micro-organisms present at a place and interacting with the atmosphere like sun light, air, water, soil and warmth and dwelling at a place like, pond, desert, forest, rock form the ecosystem as pond ecosystem, desert ecosystem forest ecosystem. So ecosystem cannot survive without the presence of light. As the flora (plants) living in that ecosystem can only make food in the presence of light and the animals (Fauna) living in that ecosystem get the food from the plants of that ecosystem. So flora in that area cannot survive in that area without light and animals living in that area will not get the food and the plants and animals will perish and the ecosystem cannot survive.

(d) Cattle go to ponds for drinking water, so they are a constituent of pond ecosystem (F)
Cattles likes tigers, lions, cows, deers, buffaloes, go to take water from the pond and return to their dwellings as tigers, deers etc. come to the forest so they form a forest ecosystem. But plants like hydrilla, vallineria, lotus etc. and animals like frogs, beetles, fish live in the pond and form the pond ecosystem. But animals like buffalo which come only to take~water cannot form a part of the pond ecosystem.

2. Match the items in Column I with as many items as possible in Column II.
Selina Concise Biology Class 8 ICSE Solutions – Ecosystems 1
Selina Concise Biology Class 8 ICSE Solutions – Ecosystems 2
Answer:

Selina Concise Biology Class 8 ICSE Solutions – Ecosystems 3
3. Rewrite the following in their correct sequence in a food chain:
(a) Snake → Grasshopper → Grass → Frog
(b) Grass → Tiger → Deer
(c) Snake → Peacock → Rat → Wheat

Answer:

(a) Grass → Grasshopper → Frog → Snake
(b) Grass → Deer → Tiger
(c) Wheat → Rat → Snake → Peacock

Long Answer Type:

Question 1.
Differentiate among primary, secondary and tertiary consumers. Give one example of each in a food chain.
Answer:
All plants produce food through photosynthesis and are categorised as self food producers i.e. these are autotrophs. There are plant eating animals called herbivores as Rabbits, deers, pigeons, cows, buffaloes etc. and insects like grasshoppers, bees, butterflies and crickets also eat plants or plant products as fruits, flowers, pollen grains and plant juices. Such animals are called primary consumers.
Animals like tigers, lions, wolves, lizards, frogs eat the primary consumers. Birds vultures, kites, eagles eat the primary consumer, (i.e. These birds are well eat the flesh of many birds like pigeons, sparrows.) These animals or birds are called secondary consumers.
Animals like snakes are eaten by the peacocks, they eat the secondary consumers and are called tertiary consumers.
Owls, eagle are top carnivore. So it is quaternary consumer.

Question 2.
Define the term (a) flora and (b) fauna.
Answer:
Flora: Plants occurring in a particular is called flora of that area i.e. vegetative growth forms flora. Flora deals with plants.
Fauna: The animals occurring in a area form the fauna of that area. Fauna deals with animals.
Flora and fauna of an area is the plants and animals found in that area.

Question 3.
List any three members each of the flora and fauna of tropical rain forests.
Answer:
Tropical rain forest are on western coast of India and in the north, east.
Flora: bamboos, ferns, shrubs (Evergreen trees).
Fauna: leopards, jungle cats, monkeys, snakes, flying squirrels, insects, snails, centipedes, millipedes.

Question 4.
Define the following terms and give two examples in each case.
(a) Symbiosis
(b) Parasitism
(c) Predation
Answer:
(a) Symbiosis: It refers to relationships between organisms of different species that show on intimate association with each other. Symbiotic relationships provide atleast one of the participating species with a nutritional advantage.
Examples of Symbiosis Relationships are of Fungus and photosynthestic alga and Microbes and cattle.

(b) Parasitism: Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Examples of Parasitism are 4 tapeworms, flukes, the plasmodium species and mosquitoes.

(c) Predation: A predator is any consumer that kills and eats another living organism in order to obtain energy. The organism being eaten is called the prey.
Examples are Lions, Deer, Wolves, Eagles.

Selina Concise Chemistry Class 8 ICSE Solutions – Carbon and Its Compounds

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Selina Concise Chemistry Class 8 ICSE Solutions – Carbon and Its Compounds

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 8 Chemistry Chapter 9 Carbon and Its Compounds. You can download the Selina Concise Chemistry ICSE Solutions for Class 8 with Free PDF download option. Selina Publishers Concise Chemistry for Class 8 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

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Selina Concise ICSE Solutions for Class 8 Chemistry Chapter 9 Carbon and Its Compounds

Points to Remember:

  1. Carbon occurs in the earth’s crust in the free as well as in the combined state.
  2. In the free state, it occurs as coal, diamond and graphite.
  3. In the combined state, carbon occurs in atmosphere (CO2) natural gas, food nutrients and carbonates.
  4. Diamond is the hardest naturally occuring substance known.
  5. Fullerenes are discovered only recently.

Exercise – I

Question 1.
Fill in the blanks.

(a) Carbon is present in both living and non-living things.
(b) The tendency of an element to exist in two or more forms but in the same physical state is called Allotropy.
(c) Crystalline and non- crystalline are the two major crystalline allotropes of carbon.
(d) Diamond is the hardest substance that occurs naturally.
(e) The name ‘carbon’ is derived from the Latin word carbo.

Question 2.
Choose the correct alternative.

(a) In combined state, carbon occurs as
(i) coal
(ii) diamond
(iii) graphite
(iv) petroleum

(b) A crystalline form of carbon is
(i) lampblack
(ii) gas carbon
(iii) sugar
(iv) fullerene

(c) Graphite is not found in
(i) Bihar
(ii) Maharashtra
(iii) Orissa
(iv) Rajasthan

(d) Diamond is used for
(i) making the electrodes of electric furnaces.
(ii) making crucible for melting metals.
(iii) cutting and drilling rocks and glass.
(iv) making carbon brushes for electric motors.

(e) Carbon forms innumerable compounds because
(i) it has four electrons in its outermost shell.
(ii) it behaves as a metal as well as a non- metal.
(iii) carbon atoms can form long chains.
(iv) it combines with other elements to form covalent compounds.

Question 3.
Write ‘true’ or ‘false’ against the following statements.

(a) Carbon constitues 0.03% of the earth’s crust. – True
(b) Graphite is the purest form of carbon. – False
(c) Coloured diamonds are costlier than colourless and transparent diamonds. – False
(d) Graphite has layers of hexagonal carbon bondings. – True
(e) Diamond is insoluble in all solvents. – True.

Question 4.
Define the following terms:
(a) Allotropy (b) Carat
(c) Crystal (d) Catenation
Answer:
(a) Allotropy: Allotropy is defined as the phenomenon due to which an element exists in two or more forms in the same physical state with identical chemical properties but with different physical properties.

(b) Carat – The weight of diamond is expressed in carats [ 1 carat = 0.2 g]

(c) Crystal – A crystal is a homogeneous solid which particles (atoms, molecules or ions) are arranged in difinite pattern due to which they have definite geometrical shape with plane surfaces e.g. sugar and sodium chloride.

(d) Catenation – The large number of organic compounds is due to the ability of carbon atom to form long chains with other carbon atoms through the sharing of electrons. This unique property of carbon is known as catenation.
selina-concise-chemistry-class-8-icse-solutions-carbon-and-its-compounds-1

Question 5.
State the terms:

(a) Substances whose atoms or molecules are arranged in a definite pattern. – Crystals.
(b) Different forms of an element found in the same physical state. – Allotropy.
(c) The property by which atoms of an element link together to form long chain or ring compounds. – Catenation

Question 6.
Name the following:

(a) The hardest naturally occurring substance. – Diamond.
(b) A greyish black non- metal that is a good conductor of electricity. – Graphite.
(c) The third crystalline form of carbon. – Fullerenes.

Question 7.
Answer the following questions:
(a) Why is graphite a good conductor of electricity but not diamond?
(b) Why is diamond very hard?
(c) What are fullerenes? Name the most common fullerenes.
(d) What impurity is present in black diamond?
(e) Explain the softness of graphite with reference to its structure.
Answer:
(a) In a graphite molecule, one valence electron of each carbon atom remains free, Thus making graphite a good conductor of electricity. Whereas in diamond, they have no free mobile electron. Thats why diamond are bad conductor electricity.

(b) A diamond is a giant molecule. The number of valence electrons in carbon atom is four. As such each carbon atom is linked with four neighboring carbon atoms. Thus forming a rigid tetrahedral structure. It is the strong bonding’that makes diamond the hardest substance.

(c) Fullerenes: Fullerenes are the third crystalline form of carbon.
Though they were discovered only recently. They have.been found to exist in interstellar dust as well as in the geological formations of the earth.
Common fullerenes are C – 32, C – 50, C – 70 and C – 76

(d) Black diamonds have copper oxide present in them as impurity.

(e) In a graphite molecule of each carbon atoms is linked with three neighboring carbon atoms. Thus forming a hexagonal arrangement of atoms. These hexagonal grouping of carbon atoms are arranged as layers or sheets piled one the top of other. The layers are held together by weak forces such that they can slide over one another. That is why graphite is soft.

Question 8.
Give two uses of (a) graphite (b) diamond.
Answer:

(a) Uses of graphite:

  1. For making the electrodes of electric furnaces.
  2. For making crucibles for melting metals due to its high melting points.

(b) Uses of Diamond:

  1. Diamond is used in jewellery as a gem
  2. It is used for cutting and drilling rocks, glass,

Question 9.
Write three differences between graphite and diamond.
Answer:
Difference between diamond and graphite.

Diamond

  1. Pure diamond is colourless and transparent.
  2. It is the hardest naturally occurring substance.
  3. It has high density i.e. 3.5 g/cm3
  4. It is bad conduct of electricity.
  5. It bums in air at 900°C to form carbon dioxide.

Graphite

  1. Graphite is greyish black opaque and shiny.
  2. It is soft and greasy to touch.
  3. It has low density i.e. 2.39 g / cm3
  4. It is good conductor of electricity.
  5. It bums in air at 700° C to form carbon dioxide.

Exercise – II

Question 1.
Fill in the blanks:

(a) Charcoal is formed when charcoal is burnt in a limited supply of air.
(b) Coal is a amorphous form of carbon.
(c) Peat is the most inferior form of coal.
(d) Wood charcoal is a bad conductor of heat and electricity.
(e) lampblack is used in making black shoe polish.

Question 2.
Choose the correct alternative

(a) Anthracite is
(i) an inferior type of coal
(ii) a superior type of coal
(iii) a cheapest form of coal
(iv) none of above

(b) Destructive distillation of coal yields
(i) coal tar
(ii) coal gas
(iii) coke
(iv) all of the above

(c) Lamp black is
(i) an amorphous form of carbon
(ii) a crystalline form of carbon
(iii) a pure form of carbon
(iv) a cluster of carbon atoms

(d) The process by which decayed plants slowly convert into coal is called.
(i) petrification
(ii) carbonisation
(ii) carbonification
(iv) fermentation

(e) The purest form of the amorphous carbon is
(i) wood charcoal
(ii) sugar charcoal
(iii) bone charcoal
(iv) lampblack

Question 3.
Write ‘true’ or ‘false’ against the following statements:

(a) Charcoal is a good adsorbent. True
(b) Coke is obtained by destructive distillation of sugar. False
(c) Activated charcoal is a good conductor of electricity. False
(d) Wood charcoal is an important constituent of gun powder. True
(e) Coal gas is used in the preparation of artificial ferilizers. False.

Question 4.
Define the following:
(a) Carbonization
(b) Adsorption
(c) Bone black
Answer: 
(a) Carbonization: The process of the slow conversion of vegetable matter into carbon-rich substances is called carbonization.
(b) Adsorption: Adsorption is the property due to which a substance absorbs gases, liquids and solids on its surface.
(c) Bone black: The Carbon content of bone charcoal is separated by treating the latter with hydrchloride acid, which dissolves the calcium phosphate. Carbon is then filtered out of the solution and in this form it is called bone black.

Question 5.
Name the following:

(a) Substances whose atoms or molecules are not arranged in a geometrical pattern. – Amorphous
(b) The best variety of coal. – Bituminous
(c) The purest form of amorphous carbon. – Anthracite
(d) An amorphous form of carbon that contains about 98% carbon. – Anthracite
(e) Mixture of carbon monoxide and hydrogen. – Water gas.

Question 7.
Answer the following questions:
(a) What is destructive distillation? What are the products formed due to the destructive distillation of coal?
(b) Why is wood charcoal used in water filters and gas masks?
(c) How is wood charcoal made locally? What other substances are formed in the process.
(d) How many carbon atoms are there in Buckminster fullerenes?
Answer: 
(a) Destructive Distillation: When a substances is heated in the absence of air. The process is called destructive distillation.
Products formed are: Coke, Coal tar, Coal gas and ammonia solution

(b) Due to its high adsorbing capacity, wood charcoal is used as gas masks to adsorb harmful gases. Wood charcoal is porous, that is why it is used to filter water.

(c) Wood charcoal is prepared when wood is heated in a limited supply of air. Locally wood charcoal is prepared by piling logs of wood one above the other with a gap in the centre of the pile. The pile is covered with wet clay to prevent the entry of air. A few holes are left at the bottom of the pile. The wood is set on fire. After some time when fire dies out, wood charcoal is left behind. The other substances are -wood tar, pyroligneous acid and wood gas.
selina-concise-chemistry-class-8-icse-solutions-carbon-and-its-compounds-2

(d) 60 carbon atoms are arranged in spherical structure in Buck minster fullerences.

Question 7.
(a) Descirbe the formation of coal,
(b) Name four types of coal with percentage of carbon present in each, with uses.
Answer:
(a) Formation of coal:- The formation of coal took millions of years. Coal was formed by the bacterial decomposition of ancient vegetable matter hurried under successive layers of the earth. Under in action of high temperature and pressure, and in the abcence of air, the decayed vegetable matter converted into coal.
(b) Types of Coal:

  1. Peat: It is light brown in colour and contains only 50 – 60% carbon. It is the most inferior form of coal.
  2. Lignite: it contains more than 60% carbon. It is brown in colour and harder than peat.
  3. Bituminous: It has 90%, 80%, 70 – 75% carbon contents. Bituminous coal is the most common variety of coal and used as house hold coal.
  4. Anthracite: It is the purest variety of coal. Its carbon contents vary between 92 – 98%. It is hard, dense and black, difficultto ignite.

Uses of coal:

  1. Coal is used as both domestic and industrial fuel.
  2. It is used to prepare coke, coal gas and coal tar.

Question 9.
Name the products formed when:
(a) wood is burnt in the absence of air.
(b) bone is heated in the absence of air.
(c) diamond is burnt in air at 900°C.
(d) graphite is subjected to high pressure and 3000°C temperature.
Answer:
(a) Wood charcoal is formed when wood is burnt in limited supply of air.
(b) Bone charcaol, bone oil and organic compound pyridine.
(c) Carbon dioxide.
(d) Artificial diamond.

Question 9.
Give two uses for each of the following:
(a) coal
(b) coke
(c) wood charcoal
(d) sugar charcoal
(e) bone charcoal
(f) lampblack
Answer: 
(a) Uses of coal

  • It is used as both a domestic and an industrial fuel.
  • It is used to prepare coke, coal gas and coal tar.

(b) Uses of coke

  • Coke is used as a smokeless fuel, in smelting furnaces.
  • It is used in the manufacturing of water and producer gas.

(c) Uses of wood charcoal:

  • Wood charcoal is used as a fuel.
  • It is an important constituent of gun powder.

(d) Sugar charcoal:

  • Sugar charcoal is mostly used as a reducing agent.
  • It is used to decolourise coloured solutions.

(e) Bone charcoal:

  • It is extensively used to decolourise cane-sugar in the process of manufacturing sugar.
  • It is also used in the manufacture of large number of phosphorous compounds.

(f) Uses of lamp black:

  • It is used in making black shoe polish.
  • It is used in the manufacture of tyres and gun powder.

Question 10.
Give balanced equations for the following chemical reactions:
(a) wood charcoal and cone, nitric acid
(b) coke and steam
(c) wood charcoal and lead monoxide.
Answer:
selina-concise-chemistry-class-8-icse-solutions-carbon-and-its-compounds-3

Exercise – III

Question 1.
(a) Name the chemicals required for the preparation of carbon dioxide in the laboratory.
(b) How will you collect the gas ?
(c) Write the balanced chemical equation for the above reaction.
(d) Draw a labelled diagram for the preparation of CO2 in the laboratory.
(e) Why is sulphuric acid not used for the preparation of carbon dioxide in the laboratory ?
Answer:
(a) Calcium carbonate and dilute hydrochloric acid.
(b) By upward displacement of air.
(c) CaCO3 + 2HCl → CaCl2 + H2O + CO2.
(d) Laboratory preparation of carbon dioxide
selina-concise-chemistry-class-8-icse-solutions-carbon-and-its-compounds-4
(e) Dilute sulphuric acid reacts with calcium carbonate. But it is not used because the calcium sulphate which is formed during the reaction is insoluble in water. It covers the marble chips and stops the reaction.
selina-concise-chemistry-class-8-icse-solutions-carbon-and-its-compounds-5

Question 2.
Write the balanced chemical equations for the preparation of carbon dioxide by:
(a) heating calcium carbonate.
(b) the action of acetic acid on sodium bicarbonate.
(c) the action of dilute sulphuric acid on sodium bicarbonate.
Answer:
selina-concise-chemistry-class-8-icse-solutions-carbon-and-its-compounds-6

Question 3.
What happens when:
(a) a lit splinter is introduced into a jar containing carbon dioxide ?
(b) moist blue litmus paper is placed in a jar containing carbon dioxide ?
(c) carbon dioxide is passed through lime water first in small amounts and then in excess ?
(d) a baking mixture containing baking powder is heated?
(e) a soda water bottle is opened ?
Answer:
(a) Lit splinter extinguishes.
(b) Blue litmus paper turns red.
(c) When CO2 is passed through lime water in small amount, it turns milky, when passed in excess milkiness disappears.
(d) Carbon dioxide is formed.
(e) When the pressure is released the bottled gas escapes with a bristling effervescence that ads fizz to the drink.

Question 4.
Give reasons for the following:
(a) An excess of carbon dioxide increases the temperature of the earth.
(b) Soda acid and foam types of fire extinguisher are not used for extinguishing electrical fires.
(c) Solid carbon dioxide is used for refrigeration of food.
Answer:
(a) Excess of carbon dioxide increases the temperature of the earth. Due to rise in temperature ice in the polar regions may melt causing floods in coastal regions island.
(b) In both of these fire extinguishers, the solutions are prepared in water, which conducts electricity. As a result an electric shock might result, which might lead to short- circuiting and another fire.
(c) Solid carbon dioxide serves as a coolant and refrigeration for preserving food articles.

Question 5.
What is a fire extinguisher ? What is the substance used in the modern type of fire extinguishers ? How is it an improvement over the soda acid-type and the foam-type fire extinguishers ?
Answer:
Fire Extinguisher— Fire extinguishers are a device in which carbon dioxide is produced in different forms for use as the extinguishing agent. It is a modem type of fire extinguisher in which liquid carbon dioxide is stored in a steel cylinder under pressure. Soda-acid and foam types of extinguisher cannot be used for extinguishing fire as they prepared in water, which conducts electricity and there can be short circuiting, causing another fire.

Question 6.
Explain the term ‘green house effect’. How can it be both beneficial and harmful for life on earth ?
Answer:
Green house effect— The trapping of the earth’s radiated energy by carbon dioxide present in air, so as to keep the earth warm, is called ‘green house effect’.
Green house is beneficial because this principle is applied to grow plants in colder regions.
Carbon dioxide increases the temperature of atmosphere. Due to rise in temperature; ice in the polar regions may melt, causing floods. So it is harmful for life on earth.

Question 7.
What steps should be taken to balance carbon dioxide in the atmosphere ?
Answer:
As global warming will cause an unbalanced ecological system, serious efforts should be made to balance the percentage of carbon dioxide in the atmosphere. Some of these steps are:

  • Growing more trees and plants.
  • Using smokeless sources of energy like solar energy, biogas, etc.
  • Using filters in the chimneys of factories and power houses.

Question 8.
State three ways by which carbon dioxide gas is added into the atmosphere.
Answer:

  1. By planting more trees.
  2. By combustion of fuels
  3. By decay of dead animals, plants and plants products.

Exercise – IV

Question 1.
Fill in the blanks:

(a) Carbon monoxide is formed when carbon is burnt in a limited supply of air or oxygen.
(b) Carbon monoxide bums in air with a pale blue flame to form carbon dioxide.
(c) Carbon monoxide is a products of incomplete combustion.
(d) A mixture of 95% oxygen and 5% carbon dioxide is called carbogen
(e) Carbon dioxide is used as a reducing agent in the extraction of pure metals from their corresponding ores.

Question 2.
Match the following.
selina-concise-chemistry-class-8-icse-solutions-carbon-and-its-compounds-7

Question 3.
How is carbon monoxide gas formed?
Answer:
Mostly carbon monoxide is formed when a large amount of carbon or its compounds is burnt in a limited supply of air or oxygen.
selina-concise-chemistry-class-8-icse-solutions-carbon-and-its-compounds-8

Question 4.
State the poisonous nature of carbon monoxide?
Answer:
Carbon monoxide is highly poisonous gas. If air containing 0.5% carbon monoxide by volume is inhaled, death can result This is because carbon monoxide combines with the haemogloblin present in the blood cells of our body to form a stable compound called carboxyl-haemoglobin. This does not allow to absorb oxygen. Thus depriving our body cells of oxygen. This cause obsruction in respiration and causes death.

Question 5.
Give two uses of carbon monoxide.
Answer:
Uses of carbon monoxide:

  • Carbon monoxide is a strong reducing agent.
  • Carbon monoxide is used in the extraction of pure metals from their ores.

Question 6.
Why is carbon monoxide called silent killer ?
Answer:
Carbon monoxide is produced by burning coal or wood in a limited supply of air. Since the gas is colourless and a barely detectable smell, people do not feel it and it can be proved as a silent killer.

Question 7.
Explain the reducing action of carbon monoxide.
Answer:
Reducing action of carbon- monoxide: Carbon monoxide is a strong reducing agent. It reduces the oxides of the less active metals to their respective metals and itself gets oxidised to carbon dioxide.
selina-concise-chemistry-class-8-icse-solutions-carbon-and-its-compounds-9

Question 8.
Write two remedies for carbon monoxide poisoning.
Answer:

  1. The victim should immediately brought out into the open.
  2. The victim should be given artificial respiration with caibogen.

Question 9.
Complete the reactions and balance them.
(a) CuO + CO →
(b) Fe2O2 + CO →
Answer:
selina-concise-chemistry-class-8-icse-solutions-carbon-and-its-compounds-10

Selina Concise Chemistry Class 8 ICSE Solutions – Matter

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Selina Concise Chemistry Class 8 ICSE Solutions – Matter

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 8 Chemistry Chapter 1 Matter. You can download the Selina Concise Chemistry ICSE Solutions for Class 8 with Free PDF download option. Selina Publishers Concise Chemistry for Class 8 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

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Selina Concise ICSE Solutions for Class 8 Chemistry Chapter 1 Matter

Exercise

Question 1.
Define:
(a) matter
(b) intermolecular force of attraction.
Answer:
(a) Matter is anything which has mass, occupies space and can be percieved by our senses.
Example: Air, Book.
(b) The molecules of matter are always in motion and attract each other with a force called intermolecular force of attraction due to which they are held together.

Question 2.
What are the three states of matter ? Define each of them with two examples.
Answer:
The three states of matter are:
solids, liquids and gases

  • Solids — A solid has a definite shape and definite volume.
    Example – wood, stone, iron, ice etc.
  • Liquid — A liquid has a definite volume but not definite shape.
    Example — water, juice, milk, oil, etc.
  • Gases — A gas neither has definite shape nor a definite volume.
    Example – air, hydrogen, oxygen, watervapour etc.

Question 3.
Define interconversion of states of matter. What are the two factors responsible for the change of states of matter?
Answer:
The process by which matter changes from one state to another and back to original state, without any change in its chemical composition is called interconversion state of matter.
Two factors responsible for change of state of matter are: change in
(i) Temperature (ii) Pressure

Question 4.
State the main postulates of kinetic theory of matter.
Answer:
The main postulates of the theory are:

  1. Matter is composed of very small particles called atoms and molecules.
  2. The constituent particles of a kind of matter are identical in all respects.
  3. These particles have space or gaps between them which is known as interparticular or intermolecular space.
  4. There exists a force of attraction between the particles of matter which holds them together. This force of attraction is known as interparticular or intermolecular force of attraction.
  5. Particles of matter are always in a state of random motion and possess kinetic energy, which increases with increase in temperature and vice-versa.

Question 5.
What happens to water if
(a) it is kept in a deep freezer
(b) it is heated
Explain the phenomenon of change of state of water.
Answer:
(a) When water is kept in a deep freezer, it gets cooled and change into ice at 0°C ice.
selina-concise-chemistry-class-8-icse-solutions-matter-1
(b) Water on heating changes into steam at 100°C
selina-concise-chemistry-class-8-icse-solutions-matter-2
Phenomenon of change of state of water:
Water is a liquid under ordinary conditions but, when it is kept in a deep freezer, it changes into ice at 0°C and when ice is kept at room temperature again changes back into liquid water.
Similarly, water on heating change into steam at 100°C, which on cooling changes back into liquid water. But there is no change in the chemical composition of water. When its state changes from liquid to solid or liquid to gaseous state.
selina-concise-chemistry-class-8-icse-solutions-matter-3

Question 6.
(a) State the law of conversation of mass.
(b) What do you observe when, barium chloride solution is mixed with sodium sulphate solution ?
Answer:
(a) “Matter can neither be created nor be destroyed in a chemical reaction”. However, it may change from one form to another in the process.
It can also be stated as, “In a chemical reaction, the total mass of the reactants is equal to the total mass of the products”.

(b)
selina-concise-chemistry-class-8-icse-solutions-matter-4
We will observe that a white insoluble solid (precipitate) of barium sulphate is formed along with a solution of sodium chloride. Wait for ten minutes to complete the reaction and the solid formed to settle down.
Weigh the content again and note the reading.
We will observe that,
total mass of the apparatus + reactants = total mass of apparatus + products
Hence the law of conservation of mass is verified.

Question 7.
Give reasons:
(a) A gas can fill the whole vessel in which it is enclosed.
(b) Solids cannot be compressed.
(c) Liquids can flow.
(d) When magnesium is burnt in air, there is an increase in mass after the reaction.
Answer:
(a) Because, in gases, the molecules are free to move.
They are not stuck to each other and the intermolecular force of attraction is least in the gases. So the gas almost filled the whole vessel in which it is enclosed.

(b) In solids, particles are closely packed. There is a strong force of attraction and the intermolecular space is almost zero. Therefore the molecules are not free to move, which makes them hard and rigid. So solids can not be compressed.

(c) In liquids intermolecular force is weaker because the particles are not closely packed and hence there is large intermolecular space. So molecules in a liquids can move randomely and hence liquids can flow easily.

(d) When magnesium ribbon is burnt in air, a white solid, magnesium oxide is formed. The mass of magnesium oxide is
more than the mass of magnesium. This is because mass of oxygen used is not taken. If that is considered, the total mass of the reactants and the products is found to be almost equal.
selina-concise-chemistry-class-8-icse-solutions-matter-5

Question 8.
Fill in the blanks:

(a) The change of a solid into a liquid is called melting or fusion.
(b) The process in which a solid directly changes into a gas is called sublimation.
(c) The change of water vapour into water is called condensation.
(d) The temperature at which a liquid starts changing into its vapour state is evaporation or vaporisation.

Question 9.
Give two examples for each of the following:
(a) The substances which sublime.
(b) The substances which do not change their state on heating.
Answer:
(a) Camphor, iodine, naphthalene, ammonium chloride, dry ice (solid carbon dioxide), etc.
(b) Gases do not change their state on heating.
Example: O2.

Question 10.
Define:
(a) Diffusion.
(b) Brownian motion.
Answer:
(a) Diffusion: The intermixing of two or more substances due to the motion of their particles in order to get a uniform mixture is called ‘diffusion’.
(b) Brownian motion: The haphazard, random motion of suspended particles on the surface of a liquid or in air is called ‘Brownian motion’.

Question 11.
When sodium chloride is added to a definite volume of water and stirred well, a solution is formed, but there is no increase in the level of water. Why?
Answer:
This is because there is some space between the particles of water in which the salt particles get accomodated when dissolved.

Question 12.
What do you observe when a gas jar which appears empty is inverted over a gas jar containing Bromine vapours? Name the phenomenon.
Answer:
When a gas jar full of bromine vapours (reddish brown) is inverted over a gas jar containing air over it. It is observed that after sometime, the reddish brown vapours of bromine also spread out into the upper jar. This mixing is called diffusion. The rate of diffusion is the fastest in gases and the slowest in solids. It increases with an increase in temperature.

Question 13.
Why can a piece of chalk be broken easily into smaller pieces while a coal piece cannot be broken easily?
Answer:
The particles of matter have force acting between them. This force keeps the particles together. The strength of this force of attraction is lesser in chalk, hence it could be broken easily into smaller pieces.
But the strength of inter-molecular force of attraction is very strong in coal, therefore it is not possible to break them into small pieces.

Selina Concise Chemistry Class 8 ICSE Solutions – Elements, Compounds and Mixtures

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Selina Concise Chemistry Class 8 ICSE Solutions – Elements, Compounds and Mixtures

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 8 Chemistry Chapter 3 Elements, Compounds and Mixtures. You can download the Selina Concise Chemistry ICSE Solutions for Class 8 with Free PDF download option. Selina Publishers Concise Chemistry for Class 8 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

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Selina Concise ICSE Solutions for Class 8 Chemistry Chapter 3 Elements, Compounds and Mixtures

Exercise 3(A)

Question 1.
Define: (a) Elements (b) Compounds
Answer:
(a) Elements: Element is a substance which cannot be broken further into simpler substances and has a definite set of properties. Elements are made up of only one kind of atoms.
(b) Compounds: Compounds are pure substances composed of two or more elements in definite proportion by mass and has properties, entirely different from those of its constituents elements.
Compound, are made up of different types of atoms combined chemically.

Question 2.
Give two examples for each of the following:
(a) Metals (b) Non-metals
(c) Metalloids (d) Inert gases
Answer:
(a) Metals: Iron, silver, gold.
(b) Non-metals: Carbon, sulphur, oxygen.
(c) Metalloids: Antimony, silicon, boron.
(d) Inert gases: Helium, argon, neon.

Question 3.
Differentiate between:
(a) Pure and impure substances
(b) Homogenous and heterogenous substances
Answer:
(a) Pure substances —

  1. Pure substances have definite composition and definite physical and chemical properties.
  2. They are all homogeneous i.e. their composition is uniform throughout the bulk.
  3. Examples: Elements and compounds.

Impure substances —

  1. Impure substances are made up of two or more pure substances mixed together in any proportion.
  2. They may be homogeneous or hetergeneous i.e. their composition is not uniform throughout the bulk.
  3. They are all mixtures.
    Examples: air, sea water, petroleum, a solution of sugar in water are all impure substances.

(b) Homogeneous mixture — is a mixture where the components that make up the mixture are uniformly distributed throughout the mixture.
Example — air, sugar water, rain water.
Heterogeneous mixture — is a mixture, where the components of the mixture are not uniform or have localized regios with different properties.
Example—Cereal in milk, vegetable soup.

Question 4.
Write the chemical name of the following and also give their molecular formulae:
(a) Baking soda (b) Vinegar
(c) Marble (d) Sand
Answer:
(a) Sodium bicarbonate (Baking soda) — NaHCO3
(b) Acetic acid (Vinegar) — CH3COOH
(c) Calcium carbonate (Marble) — CaCO3
(d) Silicon dioxide (Sand) — SiO2

Question 5.
Name:
(a) a soft metal
(b) a metal which is brittle
(c) a non-metal which is lustrous
(d) a liquid metal
(e) a metal which is a poor conductor of electricity.
(f) a non-metal which is a good conductor of electricity.
(g) a liquid non-metal
(h) the hardest naturally occurring substance
(i) an inert gas
Answer:
(a) Gold
(b) Zinc
(c) Iodine
(d) Mercury
(e) Tungsten
(f) Graphite
(g) Bromine
(h) Diamond
(i) Neon, helium

Question 6.
How is sodium chloride different from its constituent elements ?
Answer:
The properties of sodium chloride are completely different from those of sodium and chlorine. Sodium is a soft, highly reactive metal. Chlorine is a poisonous non-metallic gas while sodium chloride is a very useful non poisonous compound which is added to our food to get minerals and also to add taste to it.

Question 7.
Why is iron sulphide a compound ?
Answer:
Iron sulphide is a compound which can be broken into the elements iron and sulphur they both have different properties. The properties of compound are entirely different from there of its constituents elements.

Exercise 3(B)

Question 1.
Classify the following substances into compounds and mixtures:
Answer:
Carbon dioxide, air, water, milk, common, salt, blood, fruit juice, iron sulphide.
Carbon dioxide — (Compound)
air — (Mixture)
water — (Compound)
milk — (Mixture)
common salt — (Compound)
blood — (Mixture)
fruit juice — (Mixture)
iron sulphide — (Compound)

Question 2.
Give one example for each of the following types of mixtures
(a) solid-solid homogenous mixture
(b) solid-liquid heterogenous mixture
(c) misicible liquids
(d) liquid-gas homogenous mixture
Answer:
(a) Solid-solid homogenous mixture — Alloys of metals e.g. brass, bronze stainless steel etc.
(b) Solid-liquid heterogenous mixture — Sand and water, mud and water, sugar and oil.
(c) Misicible liquids — water and ethanol.
(d) Liquid-gas homogenous mixture — Air

Question 3.
Suggest a suitable technique to separate the constituents of the following mixtures. Also give the reason for selecting the particular method.
(a) Salt from sea water
(b) Ammonium chloride from sand
(c) Chalk powder from water
(d) Iron from sulphur
(e) Water and alcohol
(f) Sodium chloride and potassium nitrate
(g) Calcium carbonate and sodium chloride
Answer:

(a) The technique used to separate the salt from seawater is Evaporation.
Reason – Because this method is used to separate the components of the homogeneous solid-liquid mixture. In this method, sea water is collected in a shallow bed and allowed to evaporate in the sun. When all the water is evaporated, salt is left behind. By this method, we only get solid and liquid is evaporated in its vapour form.

(b) Technique used to separate Ammonium chloride from sand is sublimation.
Because this method is used for solid mixtures in which one of the components can sublime on heating. In this method, Ammonium chloride changes into vapours on heating and salt is left behind.

(c) Technique used to separate chalk powder from water is filtration.
Reason – Because this process is used to separate the components of a heterogeneous solid-liquid mixture in which solids are lights and insoluble in liquids. Substances used as filters are sand filter paper at C. These filters allows the liquid to pass through them, but not solids.

(d) Technique to separate iron from sulpher is magnetic separation.
Because, this method is used when one of the component of mixture is Iron. Iron gets attracted towards the magnet and hence get separated.

(e) Technique used to separate water and Alcohol is Fractional Distillation.
Because in this method, the vapours of water is left behind in the original vessel as the alcohol boils at lower temperature than water. Thus these two liquids can be separated.

(f) Technique used is Fractional-crystallisation.
Because: This method is used when solubility of solid components of mixture and different in the same solvent. Here, sodium chloride and potassium nitrate. Both are soluble in water but solubility of potassium nitrate is more.

(g) Technique used is Solvent Extraction Method: Because, by this method, salts get dissolve in water while calcium carbonate being insoluble in water settles down in the container. And hence get separated about.

Question 4.
(a) Define mixture.
(b) Why is it necessary to separate the constituents of a mixture.
(c) State four differences between compounds and mixtures.
Answer:
(a) “Mixtures can be defined as. a kind of matter which is formed by mixing two or more pure substances (elements and compounds) in any proportion, such that they do not undergo any chemical change and retain their individual properties. Therefore they are impure substances.

(b) Because: The mixtures contain unwanted substances which may be harmful and may degrade the properties of mixtures. So we, need to separated them and extract useful substances.
This is necessary because
(i) It removes unwanted and harmful substances
(ii) to obtain pure and useful substances them.
Example: Sea water is rich in common salt which is an important ingredient of our food to add taste and nutrients. But sea water, cannot be directly used to get the salt.
Hence, it is necessary to separate both.

(c) Compound

  1. A compound is formed from its constituent elements as a result of chemical reaction.
  2. A compound is always homogeneous in nature.
  3. In a compound the elements are present in a fixed ratio by weight.
  4. The components of a compound can’t be separated by physical methods but can be separated by chemical methods only.
  5. The properties of a compound are different from those of its elements.
  6. The formation of a compound from its elements is accompanied by energy changes.

Mixture

  1. A mixture is obtained form its (elements, compounds) components as a result of physical change.
  2. The mixtures can be homogeneous or heterogeneous.
  3. In a mixture the components can be present in any ratio.
  4. The components of a mixture can be separated by physical methods only.
  5. The properties of a mixture lie between those of-its components.
  6. The formation of a mixture from its constituents is not accompanied by energy changes.

Question 5.
(a) What is chromatography ? For which type of mixture is it used ?
(b) What are the advantages of chromatography.
Answer:
(a) This is one of the latest techniques to separate the coloured components of a mixture when all the components are very similar in their properties. Example: Components of ink are separated by this method. Ink is a mixture of different dyes, which are separated by chromatography because some of the dyes are less soluble and some are more soluble in a solvent.

(b)

  1. A very small quantity of the substance can be separated.
  2. Components with very similar physical and chemical properties can be separated.
  3. It identifies the different constitutes of a mixture.
  4. It also helps in quantitive estimation of components of a mixture.

6. Choose the most appropriate answer from the options given below:

(a) a mixture of sand and ammonium chloride can be separated by

  1. filtration
  2. distillation
  3. sublimation
  4. crystallisation

(b) A pair of metalloids are

  1. Na and Mg
  2. B and Si
  3. C and P
  4. HeandAr

(c) Which of the following property is not shown by compounds?

  1. They are heterogeneous.
  2. They are homogeneous.
  3. They have definite molecular formulae.
  4. They have fixed melting and boiling points.

(d) A solvent of Iodine is

  1. Water
  2. Kerosene oil
  3. Alcohol
  4. Petrol

(e) Which of the gas is highly soluble in water ?

  1. Ammonia
  2. Nitrogen
  3. Carbon monoxide
  4. Oxygen

Selina Concise Chemistry Class 8 ICSE Solutions – Language of Chemistry

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Selina Concise Chemistry Class 8 ICSE Solutions – Language of Chemistry

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APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 8 Chemistry Chapter 5 Language of Chemistry. You can download the Selina Concise Chemistry ICSE Solutions for Class 8 with Free PDF download option. Selina Publishers Concise Chemistry for Class 8 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

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Selina Concise ICSE Solutions for Class 8 Chemistry Chapter 5 Language of Chemistry

Points to Remember:

  • The valency of an element is the number of electrons donated or accepted by its ‘atom’ during chemical combination.
  • There are some elements with more than one valency e.g., iron, copper, tin, lead.
  • Two or more different non-metals that collectively accept or donate one or more electrons and become negatively or positively charged in the process are called radicals.
  • A chemical reaction involves the transformation of original substance into an altogether new substance(s).
  • A chemical reaction can be represented with the help of the symbols or the formulae of the elements and the compounds taking part in that reaction. This gives a chemical equation.
  • Certain necessary conditions for a chemical reaction to happen are — close contact, solution form, heat, light and catalyst.
  • Characteristics of chemical reactions are — change of colour, evolution of a gas, formation of a precipitate, change of state, change of smell and evolution/absorption of heat.
  • A complete chemical equation symbolically represents the reactants, products and their physical states.
  • The substances that react with each other are called reactants and they are represented on the left hand side of the equation. The substances that are formed as a result of the reaction are called products. They are represented on the right hand side of the equation.
  • A chemical equation needs to be balanced to make it follow the law of the conservation of mass.
  • The law of conservation of mass states that mass can be neither created nor destroyed, it can only be transformed from one form to another.
  • A chemical equation gives both qualitative and quantitative information about the reactants and products.

ACTIVITY 1
Write the names and symbols of the first twenty elements that you have studied in class VI & VII.
Answer:
selina-concise-chemistry-class-8-icse-solutions-language-of-chemistry-1

ACTIVITY 2
Write the molecular formulae of:

  1. Copper oxide
  2. Iron (III) chloride
  3. Sodium hydroxide
  4. Iron (II) sulphide
  5. Lead (II) oxide
  6. Hydrogen nitrate (nitric acid)
  7. Hydrogen sulphate (sulphuric acid)
  8. Calcium hydroxide
  9. Magnesium carbonate
  10. Ammonium carbonate

Answer:

  1. Copper oxide – CuO
  2. Iron (III) chloride – FeCl3
  3. Sodium hydroxide – NaOH
  4. Iron (II) sulphide – FeS
  5. Lead (II) oxide – PbO
  6. Hydrogen nitrate (nitric acid) – HNO3
  7. Hydrogen sulphate (sulphuric acid) – H2SO4
  8. Calcium hydroxide – Ca(OH)2
  9. Magnesium carbonate – MgCO3
  10. Ammonium carbonate – (NH4)2CO3

ACTIVITY 3
Write the molecular formula for each of the following compounds:

  1. Sulphur trioxide
  2. Iron (II) sulphide and
  3. Ammonia

Find the number and names of elements present in them and calculate their molecular masses.
Answer:
1. Sulphur trioxide

  1. A molecule of sulphur trioxide is represented by the formula SO3.
  2. The elements present in it are sulphur dioxide and oxygen.
  3. One molecule of sulphur trioxide has one atom of sulphur and three atoms of oxygen.
  4. Molecular mass of sulphur trioxide (SO3)
    = 32 + 3 x 16
    = 32 + 48 = 80 amu.

2. Iron (II) sulphide

  1. A molecule of iron (II) sulphide is represented by the formula FeS.
  2. The elements present in it are iron and sulphur.
  3. One molecule of iron (II) sulphide has one atom of iron and one atom of sulphur.
  4. Molecular mass of iron (II) sulphide (FeS)
    = 55.5 + 32
    = 87.5 amu.

3. Ammonia

  1. A molecule of ammonia is represented by the formula NH3.
  2. The elements present in it are nitrogen and hydrogen.
  3. One molecule of ammonia has one atom of nitrogen and three atoms of hydrogen.
  4. Molecular mass of ammonia (NH3)
    = 14 + 3 x 1
    = 14 + 3
    = 17 amu.

Exercise

Question 1.
Define:
(a) Radical
(b) Valency
(c) Molecular formula
Answer:
(a) Radical: A radical is an atom of an element or a group of atoms of different elements that behaves as a single unit with a positive or negative charge on it.
(b) Valency: It is the number of electrons donated or accepted by the valence shell of an atom during chemical combination.
(c) Molecular formula: It is a symbolic representation of a molecule. It shows the number of atoms of each element present in it. These atoms combine in whole number to form the molecule.

Question 2.
Give the symbols and valencies of following radicals:
(a) Hydroxide (b) Chloride
(c) Carbonate (d) ammonium
(e) Nitrate
Answer:
selina-concise-chemistry-class-8-icse-solutions-language-of-chemistry-2

Question 3.
Write the molecular formula for the oxide and sulphide of following elements.
(a) Sodium (b) Calcium
(c) Hydrogen
Answer:
(a) Sodium oxide Na2O
Sodium sulphide Na2S
(b) Calcium oxide CaO
Calcium sulphide CaS
(c) Hydrogen oxide H2O
Hydrogen sulphide H2S

Question 4.
Write the molecular formulae for the following compounds and name the elements present.
(a) Baking soda (b) Common salt
(c) Sulphuric acid (d) Nitric acid
Answer:
(a) Baking soda — NaHCO3
Elements present in Baking soda are sodium, hydrogen, oxygen and carbon.
(b) Common salt — NaCl
Element present are: Sodium and chlorine.
(c) Sulphuric acid — H2SO4
Element present are: Hydrogen, sulphur and oxygen.
(d) Nitric acid — HNO3
Elements present are: Hydrogen, nitrogen and oxygen.

Question 5.
The valency of aluminium is 3. Write the valency of other radicals present in the following compounds.
(a) Aluminium chloride
(b) Aluminium oxide
(c) Aluminium nitride
(d) Aluminium sulphate
Answer:
(a) Aluminium chloride — (AlCl3) here valency of Al is 3.
Other radical – Chloride (Cl–)
Valency of chloride = 1
(b) Aluminium oxide — (Al2O3)
Here valency of Al is 3
Other radical present = oxide (O2-)
Valency of O2- = 2
(c) Aluminium nitride — (Al N)
Here valency of aluminium = 3
Another radical = Nitride (N3-)
Valency of nitride (N3-) = 3
(d) Aluminium sulphate — Al2(SO4)3
Here valency of aluminium is 3
Another radical = Sulphate (SO42-)
Valency of (SO42-) = 2

Question 6.
What is variable valency ? Give two examples of elements showing variable valency.
Answer:
Certain elements exhibit more than one valency, that means they show variable valency.
Ferrous is written as Iron (II) and Ferric is written as Iron (III).

Metal Radicals Valency
Iron Ferrous [Iron (II)]
Ferric [Iron (III)]		 2
3
Copper Cuprous [Copper (I)]
Cupric [Copper (II)]		 1
2

Question 7.
(a) What is a chemical equation ?
(b) Why it is necessary to balance a chemical equation ?
(c) What are the limitations of a chemical equation ?
Answer:
(a) Chemical Equation— A chemical equation is the symbolic representation of a chemical reaction using the symbols and the formulae of the substances involved in the reaction.
(b) A chemical equation needs to be balanced so as to make the number of the atoms of the reactants equal to the number of the atoms of the products.
(c)

  1. It does not inform about the physical states of the reactants and the product i.e. whether they are solids, liquids and gases.
  2. It does not inform about the concentration of reactants and products.
  3. It does not inform about the time taken for the completion of the reaction.
  4. It does not inform about the rate at which a reaction proceeds.
  5. It does not inform about the heat changes during the reaction i. e. whether the heat is given out or absorbed.
  6. It does not inform about the conditions such as temperature, pressure, catalyst etc. which affect the reaction.
  7. It does not inform about the nature of the reaction i.e. whether it is reversible or irreversible.

Question 8.
What are the ways by which a chemical equation can be made more informative ?
Answer:
A chemical equation can give more informations in the following ways:

  1. The physical state of the reactants and products can be indicated by putting (s) for solid, (l) for liquid, (g) for gas and (aq) for aqueous state.
  2. Evolution or absorption of heat during the reaction can be denoted by adding or subtracting a heat term on the product side.
  3. Temperature, pressure and catalyst can be indicated above the arrow (→ or =) separating the reactants and products.
  4. Concentration of reactants and products are indicated by adding word (dil) for dilute and (cone) for concentrated before their formulae.
  5. By the sign → or \(\rightleftharpoons \) information about irreversible and reversible reactions can be obtained.

Question 9.
State the law of conservation of mass.
Answer:
Law of conservation of mass: It states that mass can neither be created nor destroyed in a chemical reaction. During any change (physical or chemical), matter is neither created nor destroyed. However it may change from one form to another.
selina-concise-chemistry-class-8-icse-solutions-language-of-chemistry-3
Experimental Verification of Law of Conservation of Mass

Requirements: H-shaped tube called Landolt’s tube, Sodium chloride solution, silver nitrate solution, etc.
Procedure: A specially designed H-shaped tube is taken. Sodium chloride solution is taken in one limb of the tube and silver nitrate solution in the other limb as shown in figure.
Both the limbs are now sealed and weighed. Now the tubes is averted so that the solutions can mix up together and react chemically. The reaction takes place and a white precipitate of silver chloride is obtained.
selina-concise-chemistry-class-8-icse-solutions-language-of-chemistry-4
The tube is weighed again. The mass of the tube is found to be exactly the same as the mass obtained before inverting the tube.
Thus, this experiment clearly verifies the law of conservation of mass.

Question 10.
Differentiate between:
(a) Reactants and products
(b) A balanced and an unbalanced chemical equation
Answer:
(a) Reactants and products

Reactants

  1. The substances that react with one another are called reactants.
  2. Reactants are written on the left hand side of equation.

Products

  1. The new substances formed are called products.
  2. Products are written on the right hand side of equation.

(b) A balanced and an unbalanced chemical equation

Balanced chemical

  1. A balanced chemical reaction is the one in which the number of atoms of each element on the reactant side is equal to the number of atoms of that element on the product side.
  2. Ex- H2 + Cl2 → HCl

Unbalanced chemical

  1. Number of elements on reactant side are not equal to the number of elements on product side.
  2. Ex- H2 + Cl2 → 2HCl

Question 11.
Balance the following equations:
selina-concise-chemistry-class-8-icse-solutions-language-of-chemistry-5
Answer:
selina-concise-chemistry-class-8-icse-solutions-language-of-chemistry-6

Question 12.
12. Write balanced chemical equations for the following word equations:
(a) Iron + Chlorine → Iron (III) chloride
(b) Magnesium + dil sulphuric acid → Magnesium sulphate + water
(c) Magnesium + oxygen → Magnesium oxide
(d) Calcium oxide + water → Calcium hydroxide
(e) Sodium + chlorine → Sodium chloride
Answer:
(a) Iron + Chlorine → Iron (III) chloride
4Fe + 3Cl2 → 2F2Cl3
(b) Magnesium + dil sulphuric acid → Magnesium sulphate + water
2Mg + 2H2SO4 → 2MgSO4 + 2H2
(c) Magnesium + oxygen → Magnesium oxide
2Mg + O2 → 2MgO
(d) Calcium oxide + water → Calcium hydroxide
CaO + H2O → Ca(OH)2
(e) Sodium + chlorine → Sodium chloride
2Na + Cl2 → 2NaCl

Question 13.
What information do you get from the following chemical equation:
Zn(s) + 2HCl (dil) → ZnCl2 (aq) + H2(g)
Answer:
This gives zinc chloride and hydrogen. The word equation is:
Zinc + Hydrochloric acid → Zinc chloride + Hydrogen
Formulae for the products are ZnCl2 and H2

Selina Concise Chemistry Class 8 ICSE Solutions – Atomic Structure

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Selina Concise Chemistry Class 8 ICSE Solutions – Atomic Structure

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 8 Chemistry Chapter 4 Atomic Structure. You can download the Selina Concise Chemistry ICSE Solutions for Class 8 with Free PDF download option. Selina Publishers Concise Chemistry for Class 8 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

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Exercise

1. Fill in the blanks.

(a) Dalton said that atoms could not be divided
(b) An ion which has a positive charge is called a cation.
(c) The outermost shell of an atom is known as valence shell.
(d) The nucleus of an atom is very hard and dense.
(e) Neutrons are neutral particles having mass equal to that of protons.
(f) Isotopes are the atoms of an element having the same atomic number but a different mass number.

2. Write ‘true’ or ‘false’ for the following statements:

(a) An atom on the whole has a positive charge.
false
(b) The maximum number of electrons in the first shell can be 8.
false
(c) The central pad of the atom is called nucleus.
True.

3. Give the following a suitable word/phrase.

(a) The sub-atomic particle with negative charge and negligible mass.
(b) Protons and neutrons present in the nucleus.
(c) The electrons present in the outermost shell.
(d) Arrangement of electrons in the shells of an atom.
(e) The number of protons present in the nucleus of an atom.
(f) The sum of the number of protons and neutrons of an atom.
(g) Atoms of same element with same atomic number but a different mass number.
(h) The smallest unit of an element which takes part in a chemical reaction.

Answer:

(a) Neutron
(b) Mass number
(c) Valency
(d) Orbits or Valence shells
(e) Atomic number
(f) Mass number
(g) Isotopes
(h) Atom

4. Multiple Choice Questions

(a) The outermost shell of an atom is known as

  1. valency
  2. valence electrons
  3. nucleus
  4. valence shell

(b) The number of valence electrons present in magnesium is

  1. two
  2. three
  3. four
  4. five

(c) The sub atomic particle with negative charge is

  1. proton
  2. neutron
  3. electron
  4. nucleon

(d) If the atomic number of an atom is 17 and mass number is 35 then number of neutron will be

  1. 35
  2. 17
  3. 18
  4. 52

(e) The number of electrons in an atom is equal to number of

  1. protons in a neutral atom
  2. neutrons in a neutral atom
  3. nucleons in a neutral atom
  4. none of the above

(f) The sum of number of protons and number of neutrons present in the nucleus of an atom is called its

  1. mass number
  2. atomic number
  3. number of electrons
  4. all of the above

Question 5.
Name three fundamental particles of the atom. Give the symbol with charge, on each particle.
Answer:
The fundamental particles of the atom are: electrons, protons and neutrons.

Particle Symbol Charge
electron e– -1 or 1.602 x 10-19 C. Where -1 represent its one unit negative electrical charge
proton p+ + 1 or 1.602 x 10-19 C. Where +1 represents one unit +ve electrical charge.
neutron no 0

Question 6.
Define the following terms:
(a) Atomic number
(b) Mass number
(c) Nucleons
(d) Valence shell
Answer:
(a) Atomic number: Atomic number refers to the number of protons present in an atom. It is denoted by Z. Example: An atom of oxygen contains 8 proton Therefore its atomic number is 8.
(b) Mass number: Mass number refers to the sum of the number of protons and neutrons present in the nucleus of an atom and denoted by A Mass number = Number of protons + Number of neutrons.
(c) Nucleons: The protons and neutrons collectively are known as nucleons.
(d) Valence Shell: The outermost shell of an atom is known as its valence shell.

Question 7.
Mention briefly the salient features of Dalton’s atomic theory (five points).
Answer:
Salient features of Dalton’s atomic theory:

  1. Matter consists of very small and indivisible particles called atoms, which can neither be created nor can be destroyed.
  2. The atoms of an element are alike in all respects i.e. size, mass, density, chemical properties but they differ from the atoms of other elements.
  3. Atoms of an element combine in small numbers to form molecules of the element.
  4. Atoms of one element combine with atoms of another element in simple whole number ratio to form molecules of compounds.
  5. Atoms are the smallest units of matter that can take part in a chemical reaction during which only rearrangement of atoms takes place.

Question 8.
(a) What are the two main features of Rutherford’s atomic model?
(b) State its one drawback.
Answer:
(a) According to Rutherford’s model an atom consists of:

  1. The centrally located nucleus: The nucleus is a centrally located positively charged mass. The entire mass of the atom is concentrated in it. It is the densest part of the atom. Its size is very small as compare to the atom as a whole.
  2. The outer circular orbits: Electrons revolve in circular orbits (shell) in the space available around the nucleus. An atom is electrically neutral i.e., number of protons and electrons present in an atom are equal.

(b) Rutherford’s atomic model could not explain the stability of the atom as it is like a solar system, the sun is at the centre and the planets revolve around it, in an atom the electrons revolve around the centrally located nucleus containing protons.

Question 9.
What are the observations of the experiment done by Rutherford in order to determine the structure of an atom?
Answer:
Following were the observations made by Rutherford:

  1. Most of the alpha particle passed straight through the foil without any deflection from their path.
  2. A small fraction of them were deflected from their original path by small angles.
  3. Only a few particles bounced back.

Question 10.
State the mass number, the atomic number, number of neutrons and electronic configuration of the following atoms.
selina-concise-chemistry-class-8-icse-solutions-atomic-structure-1
Also, draw atomic diagrams for them.
Answer:
selina-concise-chemistry-class-8-icse-solutions-atomic-structure-2
selina-concise-chemistry-class-8-icse-solutions-atomic-structure-3

Question 11.
What is variable valency? Name two elements having variable valency and state their valencies.
Answer:
Variable valency: Some elements exhibit more than one valency. They are said to have variable valency, e.g. Iron, copper, tin, lead.
Iron         Fe       Fe2+ or Fe3+
Copper   cu        cu+ or cu2+

Question 12.
The atomic number and the mass number of sodium are 11 and 23 respectively. What information is conveyed by this statement.
Answer:
Atomic number = 11; No of protons = 11
Mass number = 23 = Number of protons + Number of neutrons.
No of neutrons = 23-11 = 12.

Question 13.
Draw the diagrams representing the atomic structures of the following:
(a) Nitrogen (b) Neon
Answer:
selina-concise-chemistry-class-8-icse-solutions-atomic-structure-4

Question 14.
Explain the rule with example according to which electrons are filled in various energy levels,
Answer:
The maximum number of electrons that can be present in any shell or orbit of an atom is given by the formula 2n2, where n is the serial number of the shell.
Therefore:
K shell, n = 1, no. of electrons = 2 x 12 = 2
L shell, n = 2, no. of electrons = 2 x 22 = 8
M shell, n = 3, no. of electrons = 2 x 32 = 18
N shell, n = 4, no. of electrons = 2 x 42= 32
Electrons are not accommodated in a given shell, unless the inner shells are filled.
That is, the shells are filled in a stepwise manner.
Example:
selina-concise-chemistry-class-8-icse-solutions-atomic-structure-5

Question 15.
The atom of an element is made up of 4 protons, 5 neutrons and 4 electrons. What is its atomic number and mass number?
Answer:
Protons = 4, neutrons = 5, electrons = 4
Atomic number = 4,
Mass number = 4 + 5 = 9

Question 16.
(a) What are the two main parts of which an atom is made of?
(b) Where is the nucleus of an atom situated ?
(c) What are orbits or shells of an atom ?
Answer:
(a)

  1. The centrally located nucleus
  2. The outer circular orbits.

(b) The nucleus is a centrally located positively charged mass.
(c) The circular orbits (shell present) in the space available around the nucleus on which electrons revolve are called orbits or shells of an atom.

Question 17.
What are isotopes? How does the existence of isotopes contradict Dalton’s atomic theory?
Answer:
Atoms of an element must have the same atomic number, but their mass number can be different due to the presence of different number of neutrons. These atoms of an element having different number of neutrons are called groups.
According to Dalton’s theory, all atoms of an element are similar to all respects, for example, they have the same shape, size etc. and have similar physical and chemical properties like mass, density and reactivity. Whereas isotopes of an element have atoms that are similar as they have same number of protons and electrons but differ in the number of neutrons. So, the isotopes have atoms that are not similar in all aspects.

Question 18.
Complete the table below by identifying A, B, C, D, E andF.
Answer:
selina-concise-chemistry-class-8-icse-solutions-atomic-structure-6

Selina Concise Biology Class 8 ICSE Solutions – Food Production

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Selina Concise Biology Class 8 ICSE Solutions – Food Production

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 8 Biology Chapter 9 Food Production. You can download the Selina Concise Biology ICSE Solutions for Class 8 with Free PDF download option. Selina Publishers Concise Biology for Class 8 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

Selina Class 8 Biology ICSE SolutionsChemistryPhysicsMathsGeographyHistory & Civics

Selina Concise ICSE Solutions for Class 8 Biology Chapter 9 Food Production

REVIEW QUESTIONS

Multiple Choice Questions:

1. Put a tick mark (✓) against the correct alternative in the following statements:

(i) Which one of the following is an indigenous breed of dairy cows ?

  1. Jersey
  2. Frieswal
  3. Sahiwal
  4. Dangi

(ii) Which one of the following is the common breed of buffalo found in Gujarat ?

  1. Surti
  2. Murrah
  3. Gir
  4. Mehsana

(iii) Identify the indigenous breed of poultry of India:

  1. White leghorn
  2. HH-260
  3. Aseel
  4. B-77

(iv) Which one of the following is a rabi crop

  1. Mustard
  2. Pea
  3. Rice
  4. Wheat

(v) Identify the Kharif crop:

  1. Barley
  2. Mustard
  3. Rice
  4. Wheat

(vi) One of the following is a bacterial disease of sheep and goat. Identify it.

  1. Sore mouth
  2. Rinderpest
  3. Goat pox
  4. Brucellosis

(vii) Which one of the following is a bacterial disease of cattle in which the animal gets swelling on body parts, especially on the neck ?

  1. Cow pox
  2. Anthrax
  3. Salmonellosis
  4. Rinderpest

(viii) The plants that live for more than two years are called:

  1. Annuals
  2. Perennials
  3. Biennials
  4. Triennials

(ix) Which one of the following is a viral disease of poultry?

  1. Ranikhet disease
  2. Cholera
  3. Coryze
  4. Aspergillosis

Short Answer Questions:

1. Fill in the blanks:

  1. Cattle feed made from cereals and wheat is called concentrates.
  2. Rearing of birds for egg and meat is called poultry.
  3. Animal food is rich in proteins.

2. Name the following:

  1. The popular indigienous breed of poultry of India …..
  2. Rearing of honey bee …..
  3. Architect of white revolution in India …..
  4. A kashmiri goat which gives expensive wool ….
  5. Scientist responsible for green revolution in India ……

Answer:

  1. The popular indigienous breed of poultry of India Aseel.
  2. Rearing of honey bee is called apiculture.
  3. Architect of white revolution in India Mr. Verghese Kurien.
  4. A kashmiri goat which gives expensive wool kashmiri pashmina.
  5. Scientist responsible for green revolution in India M.S. Swaminathan.

3. Match the columns

Selina Concise Biology Class 8 ICSE Solutions - Food Production 1

Answer:

Selina Concise Biology Class 8 ICSE Solutions - Food Production 2

4. Answer the following questions:

Question 1.
Name any four animals which provide us food.
Answer:
Buffalo, goat, pig, hen, fish give us food.

Question 2.
Name any two dual purpose breeds of cattle.
Answer:
Dangi and Tharparkar are dual purpose breeds of cattle.

Question 3.
Give two examples of milch animals.
Answer:
Cows, buffaloes, goat are milk yielding animals.

Question 4.
Name any two high-yielding indigenous breeds of cow.
Answer:
Gir, Sahiwal, Red sindhi are high yielding breeds of cow.

Question 5.
Name four varieties of edible fishes of India.
Answer:
Eel, Hilsa, Salmon, Sardine, Pomphret are edible fishes.

Question 6.
Name two breeds of buffaloes.
Answer:
Murrah, surti, mehsana are breeds of buffaloes.

Question 7.
Name any two diseases of cattle caused by viruses.
Answer:
Cow pox, foot and mouth disease.

Question 8.
Name any two bacterial iiseases of cattle.
Answer:
Anthrax and rinderpest are bacterial diseases of cattle.

Question 9.
What are the symptoms of foot and mouth disease ?
Answer:
Blisters on the foot and mouth, high body temperature, reduced appetite are symptoms of foot and mouth disease.

Question 10.
Name two bacterial diseases of poultry.
Answer:
Fowl cholera, salmonellosis, coryze are bacterial diseases.

5. Briefly explain the following terms:
Answer:

  1. Animal husbandry: The branch of Biology which deals with feeding, shelter, caring and breeding of domesticated animals is called animal husbandry.
  2. Sericulture: Artificial rearing of silk worm and getting of silk from the silk worms is called sericulture.
  3. Aquaculture: The production and farming of aquatic animals as fishes, prawns, shrimps, molluscs, lobsters etc. is called aquaculture.
  4. Hatcheries: We raise small nurseries where water is stored in small pits where we put fish seeds (fish eggs). From these fish eggs very small fish come out after hatching. Then these small fish are transferred to big ponds. These small nurseries where eggs hatch to give small fish are called hatcheries.
  5. Pisciculture: It deals with production and management of fishes. It is a scientific, systematic way of raising of fishes, their multiplication, their production and management. So it is used as food in a sensible way.

6. What is organic farming?
Answer:
Organic farming is the practice of raising crops without using inorganic fertilisers and pesticides. Farmers use organic manure that has been prepared scientifically. In order to maintain soil fertility, and for weed and pest control, they use a combination of crop rotation, hand weeding, mixed cropping and biological control.

Long Answer Questions:

Question 1.
Differentiate between an egger and a broiler.
Answer:
Following are the differences between the egger and the broiler:
Egger

  1. Egg laying chickens are called eggers or egg layers.
  2. The chicks are given calcium (bones, seeds) and are reared to produce eggs.
  3. Eggers should give large number of eggs as white leghorns give many eggs. Rhode island red breeds like HH-260, IBL-80, B-77.

Broiler

  1. Chickens which give us meat are called broilers.
  2. Those chicks are reared on a diet of fats so that they gain flesh on their body and these are used as broilers.
  3. Broilers should give flesh. Indigenous variety Aseel give high yield of meat and less number of eggs.

Question 2.
Name any two exotic breeds of fowl in India, and mention their usefulness
Answer:
Exotic breeds of fowl in India are as:

  1. White leghorn: Its size is small and needs less feed for maintenance. So to raise it is economical. It lays oval white eggs.
  2. Rhode island red: It serves both the purposes as it is a good egg layer and also provide enough of meat. It was raised on a farm in Rhode island of U.S.A. So it is named as Rhode island red.

Selina Concise Biology Class 8 ICSE Solutions - Food Production 3

Question 3.
What are “milch animals”? Give three examples of exotic breeds of cow.
Answer:
Milk-producing animals are known as “milch animals” e.g. cows, buffaloes, goats and camels. The milk from goats is nutritious and is sometimes preferred to cow milk. But the production of goat milk is much less than that of cows and buffaloes. Cow milk is quite nourishing and easy to digest, but as compared to buffaloes, cows produce less quantity of milk. Buffaloes are the major source of milk in our country.
Exotic (Foreign) breeds. For example. Jersey, Holstein- Friesian, and Brown Swiss.

Question 4.
What is the meaning of the term “aquaculture”? Name any three animals which can be cultured by this method.
Answer:
The term “aquaculture” is used for production or farming of useful aquatic animals in various types of water bodies. The animals which can be cultured by this method are: fish, prawns, lobsters, molluscous, etc.

Question 5.
Differentiate between food crops and cash crops and give two examples of each:
Answer:
Differences:
Food crops

  1. These are crops which are grown for food such as cereals: wheat, rice, maize, pulses, oil seeds.
  2. These grow in the plains generally.
  3. These are annuals and complete their cycle in one season as in case of wheat, rice maize, gram, beans, peas.

Cash crops

  1. These are crops which are cultivated for commercial purposes such as tea, coffee, rubber, coconut, spices.
  2. These grow in the hilly areas on the slopes as water of rain should not stand in the roots as in case of tea.
  3. These plants are perennials. These plants live for more than two years. Tea, coffee require pruning before winter.

Question 6.
What are Kharif crops ? Give the name of the most important cereal plant of such crops. Briefly describe any three methods for cultivation of Kharif crops.
Answer:
Kharif crops generally grow in rainy season. Rice is the most important cereal Kharif crop growing in India. It occupies the largest area in India. It needs rainfall from 150 to 200 cms. It requires flooded fields during its growth. It requires alluvial loamy soil.

Cultivation methods of Kharif crops:

  1. Broadcasting: After preparing the fields for growing the rice crop the seeds are thrown in the fields. This method is adopted in the areas where there is less of rain. The fields are not flooded with water. This method is being adopted in China and Japan.
  2. Dibbling: In this method seeds are dropped at regular interval in the furrows made by the plough.
  3. Transplantation: Here the seeds are soaked for 24 hours. The seeds get sprouted. Then these seeds are transferred to nurseries. Here the seeds grow and attain a height of 6” to 9” and then these seedlings are transferred to specially prepared flooded fields which have been properly ploughed. Then those seedlings start growing in the fields. Then the fields are watered and manured from time to time. Then the crop matures and ultimately for ripening they require a temperature ranging from 16°C to 20°C. When the crop become fully ripe and plants become golden yellowish, then the crop is harvested manually or with the help of combines.

Question 7.
Name the two main crop seasons of India. Give three examples of the crops grown during each season.
Answer:
The two main crops seasons in India are:

  1. Kharif season: The rainy season is from July to October and is known as the Kharif Season. The chief kharif crops are the milles, known as Bajra and Jowar, Paddy, Maize, Cotton.
  2. Rabi season: The winter season is from November to April and is known as rabi season. Wheat, Gram, Peas, Linseed and Mustard are important rabi crops.

Question 8.
List the uses of bacteria in the food industry.
Answer:
The bacterial action is involved in the following industrial processes.

  1. In the manufacture of vinegar, butter and cheese.
  2. The process of tanning hides in leather making and preparing sponges.
  3. The separation of flax and hemp fibres which are used for making linen cloth and ropes.
  4. Fermentation of green plants for the production of ensilage for animal food.
  5. Bacteria are used for forming lactic acid, vinegar, citric acid, and vitamins.
  6. For formation of antibiotics, serums and vaccines, vitamin B complex.

Question 9.
Name any one variety of edible mushrooms.
Answer:
White button mushroom (Agaricus bisporous) and paddy straw mushroom (Volvariella) the two varieties of edible mushrooms.
Five major steps in cultivation of the common edible mushroom are as below:

  1. Composting: The compost is prepared by mixing the following in certain proportions.
    • Wheat or paddy straw,
    • Chicken manure
    • Some organic and inorganic fertilizer
      This compost is kept at about 50°C for a week.
  2. Spawning: “mushroom seed” consisting of mycelium of the selected type of mushroom is introduced into the compost, and allowed to spread for a couple of days.
  3. Casting: A thin layer of soil is spread over the compost to give support to the mushroom and provide humidity. It also prevents quick drying of the compost and helps to regulate temperature.
  4. Cropping and Harvesting: The growth occurs in three stages:
    (a) Mycelium (a network of fibrous mass) grows within 2 to 6 weeks.
    (b) Tiny pin heads.
    (c) Button stage which grows bigger attaining marketable size.
    The full grown mushrooms are taken out.
  5. Preservation: Mushrooms are highly perishable. Their shelf life is increased by a variety of processes
    (a) Vacuum cooling
    (b) Giving gamma radiation and storing at 15°C
    (c) Freeze drying in a solution of citric acid, ascorbic acid and brine, etc.

Question 10.
Mention the benefits of “Green revolution” in our country.
Answer:
Green revolution: Knowledge of science has brought about manifold increase in the production of grains, pulses and other crops and led to green revolution. Factors leading to it are:

  1. development of high – yielding varities.
  2. development of early – maturing varities.
  3. disease – resistant varities.
  4. using of fertilizers and pesticides.
  5. development of drought – resistant and dwarf varities.

Dr. M.S. Swaminathan is known as the father of green revolution in India which has led to manifold increase in the production of wheat and rice using hybrid varities (wheat – Kalyan Sona and Sonalika, Rice – IR – 8 Padma, Jaya and Pusa 215, Maize – Ganga 101 and Rankit).

Question 11.
Mention the benefits of “White revolution” in our country.
Answer:
The benefits of “White Revolution” in our country:

  1. The purpose of this programme was to link the rural producer (dairy farmer) with the urban consumer.
  2. Rural farmer co-operatives were organized at the village level and connected to the urban consumer.
  3. It ensured that the dairy farmer got a major share of the price of milk which consumers pay.

The “Operation flood” ensured thre objectives:

  1. increased milk production
  2. strengthened the dairy farmer’s income.
  3. easy availability of milk at a fair price to all.

Question 12.
Write briefly the processes of

  1. wine (alcohol) making and
  2. bread making.

Answer:

The steps for making

  1. Wine (alcohol): Wine is usually made from grapes. The grapes are crushed and the juice is extracted. The juice contains sugar and wild yeast.The yeast ferments the sugar and gradually turns it into alcohol.
  2. Bread: Mix some flour and water with a small amount of sugar and yeast. This makes dough. Then leave the dough for an hour or so in a warm place. During this period the living yeast cells multiply and fermenting sugar to form alcohol give off carbon dioxide gas. The gas so produced makes the dough rise, more or less doubling its size. Then when you bake the dough in a hot oven: the heat kills the yeast and evaporates the alcohol.

Question 13.
Give any five features of good shelter for milch animals.
Answer:

  1. Animal shelter should be very clean, well ventilated and well-lit.
  2. Cattle should have proper sheds, so that animals are safe from rain, cold and heat.
  3. The floor should have a proper sloping so that urine and excreta can be disposed of easily.
  4. Animals should have proper feeding and drinking tubs.
  5. Animal shelter should be spacious and there should not be over crowding.
  6. It should have arrangements for clean fresh drinking water.
  7. The shelter should give protection from predators.
  8. Shelter should be located away from the residential areas and waste disposal sites.

Question 14.
What type of food you would suggest for cattle in order to get good quality of milk ?
Answer:s
Cattle should be given good quality type of food which is proper for their growth, development, health and for their maintenance. Animal food is feed.
This cattle feed has two types of substances.

  1. Roughage: The animals get roughage from hay (straw of cereals), berseem, cowpea, lucerne, silage, maize, bajra and other green plants.
    These plants generally provide fibrous substances and other minerals.
  2. Concentrates: These are rich in carbohydrates, proteins, fats, minerals, and vitamins, concentrates are given by.
    • Grains and seeds of bajra, maize, rye, gram, cotton, jowar, barley. These provide carbohydrates.
      Legume seeds and cotton seeds provide proteins and fats.
    • Oil cakes: These oil cakes are very good feed for the animals. These are formed from the remains of oil seeds after we get the oil from the seeds. We get oil cakes from the seeds of cotton, mustard.
    • Molasses are rich in proteins.
    • Wheat bran, rice bran, and gram bran also give concentrates.

Selina Concise Biology Class 8 ICSE Solutions – Reproduction in Humans

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Selina Concise Biology Class 8 ICSE Solutions – Reproduction in Humans

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 8 Biology Chapter 3 Reproduction in Humans. You can download the Selina Concise Biology ICSE Solutions for Class 8 with Free PDF download option. Selina Publishers Concise Biology for Class 8 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

Selina Class 8 Biology ICSE SolutionsChemistryPhysicsMathsGeographyHistory & Civics

Selina Concise ICSE Solutions for Class 8 Biology Chapter 3 Reproduction in Humans

REVIEW QUESTION

Multiple Choice Questions:

1. Put a tick mark (✓) against the correct alternative in the following statements:

(a) The testes are located within the:

  1. Penis
  2. Scrotum
  3. Ureter
  4. Urinary bladder

(b) Amoeba is most commonly reproduced by:

  1. Budding
  2. Regeneration
  3. Binary fission
  4. Multiple fission

(c) Identify the stage which is formed after the fertilisation of the egg by the sperm?

  1. Ovule
  2. Foetus
  3. Embryo
  4. Zygote

(d) Internally, the uterus opens into:

  1. Urethra
  2. Vagina
  3. Oviduct
  4. Vulva

(e) Which one of the following represents the correct sequence in the life history of a butterfly ?

  1. Egg → Larva → Adult → Pupa
  2. Egg → Pupa → Adult → Larva
  3. Egg → Larva → Pupa → Adult
  4. Egg → Pupa → Larva → Adult

Short Answer Questions:

Question 1.
Distinguish between the following pair of terms:
(a) Egg and sperm.
(b) Sexual reproduction and asexual reproduction.
(c) Budding and Regeneration.
Answer:
(a) Egg and sperm
Egg Sperm

  1. Egg is produced in the ovaries.
  2. Egg is spherical in shape with a nucleus.

Sperm

  1. Sperm is produced in the testes.
  2. Sperm has head with nucleus, middle piece and tail.

(b) Sexual reproduction and asexual reproduction.

Sexual reproduction

  1. In sexual reproduction the two sexes i.e., male and female produce special type of reproductive cells sperms in the male and eggs in the female.
  2. To produce a new individual the sperm has to reach the ovum and fuse with it. e.g. Humans, bird, reptile, etc.

Asexual reproduction:

  1. It involves the production of an offspring from a single parent without the fusion of reproductive cells (gametes).
  2. It is a rapid mode of multiplication, e.g. Lower plants and animals {Amoeba).

(c) Budding and Regeneration

Budding: Budding is a process in which buds grow on the outside of the parent body. The buds detach themselves when they are large enough.
Example: Hydra
Regeneration: Regeneration is the process that uses cell division to regrow lost body parts.
Example: Starfish, sponges

Question 2.
Define the following terms:
(a) Fetilization
(b) Implantation
(c) Puberty
Answer:
(a) Fetilization: When sperms and eggs from the opposite partners (males and females) fuse to form Zygote. It is called fertilization.
(b) Implantation: The fertilised egg (zygote) soon starts developing and by the time it reaches the uterus, a small ball of numerous cells is already formed. This is a kind of embryo which forms a pit in the wall of the uterus and gets fixed in it. This natural way of fixing of the embryo in the wall of the uterus is called implantation. This produces the state of pregnancy.
(c) Puberty: Puberty is the period during which the reproductive systems of boys and girls mature. In girls, it starts at the age of about ten and the first sign of puberty is the development of breasts. In boys, it starts at about 11 years of age of the^enlargement of the testes is its first sign. Sudden spurt in growth, shoulder girdle grows more than hip girdle.

Question 3.
State the reason why testes lie outside the abdomen in a scrotum?
Answer:
Both the testes remain in the scrotum because normal body temperature are to high, scrotum has smooth muscle tissues that keeps the testes at a cooler temperature than the body temperature 2°C to 3°C lower than the body temperature which is the most suitable temperature for sperm production.

Question 4.
Why is it important that a very large number of sperms should be present in the semen ?
Answer:
Single ejaculation of semen has 20,000,000 to 40,000,000 sperms. But only 1 or 2 sperms go into oviduct and fertilise the egg to form the Zygote. It forms embryo that forms an individual. It is the sperm in the semen that are of importance, and therefore semen quality involves both sperm quantity and quality.

Question 5.
List the structures, in their correct sequence, through which the sperms must pass from the time they are produced in the testes to the time they leave the urethra.
Answer:
Sperms are produced in testes. They pass as follows:
The testes consist of a mass of sperm producing tube. The tubes join to form ducts leading to the epididymis which in.turn leads into a muscular sperm duct. The two sperm ducts, one from each testes, open at the top of the urethra.

Question 6.
State the functions of the following:
(a) Ovary
(b) Testes
(c) Fallopian tubes
(d) Seminal vesicle
(e) Uterus
Answer:
(a) Ovary: Ovaries produce ova (eggs) and secrete female sex hormones, oestrogen and progestrone.
(b) Testes: A pair of testes are present in human male. The testes produce sperms.
(c) Fallopian tubes: There are two fallopian tubes in the human female reproductive system. Fertilization occurs in the fallopian tube. It also conveys fertilized egg to the uterus.
(d) Seminal vesicle: The function of seminal vesicle is to store sperms and to secrete seminal fluid.
(e) Uterus: The inner lining recieves, protects and nourishes embryo. Contractions of muscular wall expel baby during birth.

Question 7.
Given here is a section of the female reproductive system of human beings.
Selina Concise Biology Class 8 ICSE Solutions - Reproduction in Humans 1
(a) Name the parts labelled 1 to 4
(b) Name the part where fertilisation occurs in human beings.
Answer:
(a)

  1. Ovary
  2. Fallopian tube (Oviduct)
  3. Uterus (Inner lining or Muscular wall)
  4. Vagina

(b) Fertilisation occurs in the upper part of the oviduct. Sperm fuses withthe egg and zygote is formed this is called fertilisation.

Question 8.
Given alongside is a diagram of male reproductive system in humans. Label the parts indicated by numbers 1 to 5, and state their functions.
Selina Concise Biology Class 8 ICSE Solutions - Reproduction in Humans 2
Answer:

  1. Seminal vesicle: The seminal vesicles produce a secretion which serves as a medium for the transportation of the sperms.
  2. Prostate gland: Prostate gland which pours an alkaline secretion into the semen as it passes through the urethra.
  3. Testes: Sperms are produced in the testes.
  4. Urethra: Urethra passes through the penis and carries either urine or semen.
  5. Sperm duct: The sperm pass through the sperm ducts.

Long Answer Questions:

Question PQ.
Define the term metamorphosis. Briefly describe the various stages occurring in the life-cycle of a butterfly.
Answer:
Metamorphosis: A change in the form and often habits of an animal during normal development after embryonic stage complete transformation from an immature form to an adult form in two or more distinct stages.

Life cycle of butterfly: The butterfly lays its eggs on the leaves of the plants. The new born that comes out of the egg is called larva. It passes through various stages of development. The larva of butterfly is also called Caterpillar. It is very active. It is very voracious. It feeds and moves actively and gains size.
Selina Concise Biology Class 8 ICSE Solutions - Reproduction in Humans 3

It stops moving and eating and it is called pupa. It is a resting stage. The pupa spins thread around itself and thus is enclosed in a covering. It is called cocoon. This cocoon covers the pupa and is protective in function. During this stage it forms the features of an adult. After attaining adulthood the pupa comes out of the cocoon after breaking it as an adult butterfly. The wings of emerged butterfly are wrinkled and soft. After an hour these are fully stretched and it starts flying.

Question PQ.
What is fertilization? Describe the process in human beings.
Answer:
Fertilization: The fusion of male (sperm) and female (ova) gamete is called fertlization.

As the male performs sexual act with the female and as a result of it the semen is deposited in the vagina of the female. Thus the semen has millions of sperms. Only a few of these sperms are able to reach the upper part of the oviduct. If there is an egg in the oviduct it is fertilized by the sperm. As sperm enters the egg and this leads to the formation of zygote, this act is called fertilisation.

During fusion only the head part of the sperm, which has nucleus, enters the egg. The tail is left behind. The nucleus of the sperm and egg fuse and form the zygote. Soon this zygote becomes many called embryo and reaches the uterus and implants on the wall of the uterus and forms the foetus. Baby develops with in the gestation period of 280 days. After this the baby is delivered.

Question 1.
How does a single called fertilized egg grows into an adult in human beings?
Answer:
Fertilised egg i.e., zygote divides and redivides and forms a ball of cells. This is a kind of embryo and it reaches the uterus and gets attached to the wall of the uterus. This fixing of embryo to the uterus is called implantation. Now the embryo undergoes a process “specialisation of cells’’. It leads to the formation of different parts of the body. This process is called differentiation. It leads to the formation of various tissues and other organs and thus organ systems are formed. Organ system lead to the formation of an individual. Thus the zygote forms an embryo, it forms a baby and it forms an adult.

Question PQ.
Tabulate the important physical changes in the boys and girls that take place during puberty.
Answer:
Reproductive system of boys and girls mature during puberty. Puberty starts at 10 in girls and at 11 in boys. Testes enlarge in boys and breasts develop in girls. The following table shows the physical changed in boys and girls that take place during puberty.

Boys

  1. Testes become large
  2. Scrotal sac grows and penis becomes long.
  3. Length increases and shoulder girdle grows becomes more.
  4. Hair grow on the chest arm pits and on the sex organs.
  5. Facial hair and moustaches grow.
  6. Voice becomes hoarse and deep.

Girls

  1. Breasts become large.
  2. Ovaries become large and these release eggs. Size of uterus and vagina grows. Menstruation cycle starts.
  3. Sudden grow th takes place in length. Hip girdle becomes trough shaped, it larger than the shoulder girdle.
  4. Chest and abdomen do not have hair. But hair arise on the sex organs and the arm pits.
  5. No moustaches and facial hair.
  6. High pitch voice.

Question 2.
Describe the human female reproductive system with a labelled diagram.
Answer:
On each side of the uterus two white oval bodies lie. These are called ovaries. Eggs are produced in the ovaries. Nearer to the ovaries there lies expanded funnel shaped oviducts or fallopian tubes. The eggs go into the oviducts when released by the ovaries. The two oviducts open into the uterus. The walls of the uterus are muscular. The growing embryo lodges to the wall of the uterus. It is supplied by the food and blood through the placenta w hich is a connection betw een the growing embryo and the mother. The uterus joins the vagina. It is the vagina in which semen is lodged during sexual act. From here sperms go up into the oviduct and fertilise the egg. The urethra which brings urine from the urinary bladder opens into the.vulva just in front of the vaginal opening.
Selina Concise Biology Class 8 ICSE Solutions - Reproduction in Humans 4

Question PQ.
‘Adolescence is a crucial stage’. Justify this statement.
Answer:
During adolescence physical and emotional changes takes place in the body of boys and girls. This is period between the age of 10 to 19 and this is very critical period. Boys bear facial hair, muscular body, hair in the arm pits and on the sex organs, and have hoarse voice. The girls also have beautiful contours, raised breasts, wide lips and high pitch voice. The body increases in length in both cases. Boys and girls becomes conscious about the growth of the body. They become hesitant and shy to each other. They become body conscious and spend lot of time on dressing up and grooming. Hormonal level increases in their body and become restless.

Hormones affect their brains and control their emotions and moods. They cherish the company of their own sexes and show the attraction for the opposite sex. Thus it is very strange and crucial stage in their life. So adolescence is a very crucial stage in the life of the boys and the girls.

Selina Concise Biology Class 8 ICSE Solutions – Transportation in Plants

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Selina Concise Biology Class 8 ICSE Solutions – Transportation in Plants

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 8 Biology Chapter 1 Transportation in Plants. You can download the Selina Concise Biology ICSE Solutions for Class 8 with Free PDF download option. Selina Publishers Concise Biology for Class 8 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

Selina Class 8 Biology ICSE SolutionsChemistryPhysicsMathsGeographyHistory & Civics

Selina Concise ICSE Solutions for Class 8 Biology Chapter 1 Transportation in Plants

REVIEW QUESTIONS

Multiple Choice Questions:

1. Put a tick mark (✓) against the correct alternative in the following statements:

(a) Diffusion occurs when molecules move:

  1. from lower concentration to higher concentration.
  2. from higher concentration to lower concentration through a membrane.
  3. from higher concentration to lower concentration.
  4. when energy is used.

Answer: (3) from higher concentration to lower concentration.

(b) Ascent of sap in plants takes place through:

  1. Cortex
  2. Epidermis
  3. Xylem
  4. Phloem

Answer: (3) Xylem

(c) If the xylem vessels of a plant are plugged:

  1. The leaves will turn yellow
  2. No food will be made
  3. The plant will wilt (shrivel)
  4. The plant will continue to grow

Answer: (3) The plant will wilt (shrivel)

(d) Force responsible for the ascent of sap is:

  1. Capillary force
  2. Root pressure
  3. Transpirational pull
  4. All the three

Answer: (4) All the three

(e) Raisins swell when put in:

  1. Rain water
  2. Tap water
  3. Mustard oil
  4. Saturated sugar solution

Answer: (1) Rain water

(f) The root-hairs are suited for absorbing water from the soil because:

  1. They have a large surface area
  2. They have a semi-permeable membrane
  3. They contain a solution of higher concentration than the surrounding water.
  4. All the three.

Answer: (4) All the three.

(g) Transpiration is defined as:

  1. the rise of water up to the stem of a plant.
  2. the elimination of water with dissolved water products.
  3. the loss of water as water vapour from the aerial parts of a plant.
  4. the loss of water as water vapour from the roots as well as the leaves of the plant.

Answer: (3) the loss of water as water vapour from the aerial parts of a plant.

(h) Which one of the following favours the fastest transpiration rate ?

  1. A cool, humid, windy day,
  2. A hot, humid, windy day,
  3. A hot, humid, still day,
  4. A hot, dry, windy day.

Answer: (4) A hot, dry, windy day.

Short Answer Questions:

Question 1.
An experiment was set up as shown in the figure below. After some time, the Water level in test tube A fell down but not in test tube B.
Selina Concise Biology Class 8 ICSE Solutions – Transportation in Plants 1
Why was there a fall in the water level of test tube A and not in that of test-tube B ?
Answer:
In test tube A the water level falls because the water was absorbed by the plant through its roots dipped in water. Here no water loss occurs due to evaporation from the water surface due to presence of oil.
In test tube B the water level remains unchanged as it does not contain a rooted plant. Due to the presence of oil on surface no water loss occurs due to evaporation.

Question 2.
How are roots useful to the plants? Give any two points.
Answer:
Roots are useful to the plants in the following way:

  1. It absorbs water and minerals from the soil and transport it upward to various parts of a plant.
  2. Roots fix the plant firmly in the ground.

Question 3.
What do xylem vessels carry?
Answer:
The xylem vessels carry the water and minerals absorbed by the roots to the stem and leaves.

Question 4.
Name the plant tissue which helps in carrying the food to different parts.
Answer:
Phloem.

Question 5.
Define the terms:
(a) semi-permeable membrane
(b) osmosis.
Answer:

(a) Semi-permeable membrane: It is a membrane that allows the movement of solvent molecules (e.g. water molecules) through it but prevents the movement of solute particles (e.g. sugar or salt molecules).
For example: Egg membrane, parchment membrane, cellophane paper etc. are semi-permeable membranes.

(b) Osmosis: The diffusion of water molecules through a semi-permeable membrane from a region where water is more concentrated to a region where it is less concentrated is called osmosis.
In other words, osmosis is the diffusion of water from its pure state or dilute solution into a stronger or concentrated solution through a semi-permeable membrane.

Question 6.
Under what conditions do plant transpire (a) more quickly and (b) most slowly?
Answer:
(a) Transpiration is faster on hot summer days as compared to cold winters.
(b) Transpiration is reduced if the air is humid. Air cannot hold any water molecules when it is already laden with moisture (humidity).

Question 7.
Given here is an enlarged diagram of a part of the root. Draw arrows on the diagram to show the movement of water passing through different parts.
Selina Concise Biology Class 8 ICSE Solutions – Transportation in Plants 2
Answer:
Path of water through the root hair to the xylem vessels.
Selina Concise Biology Class 8 ICSE Solutions – Transportation in Plants 3

Question 8.
Why is the structure of the root hair is quite suitable for absorbing water from the soil ?
Answer:
The root hair are suitable for absorbing water from the soil in the following three ways:

  1. The root hairs present a large surface area. More the surface area, greater is absorption.
  2. The cell wall is of cellulose nature and forms permeable membrane and the plasma membrane around the vacuole forms the semi-permeable membrane.
  3. Root hairs have solution (cell sap) of a higher concentration than the surrounding soil water.

Selina Concise Biology Class 8 ICSE Solutions – Transportation in Plants 4
Fig. Unicellular root hairs through the soil particles

Question PQ.
In an experimental set-up, a dye was placed at the bottom of a beaker filled with water as shown in figure A, below. After some time, the entire water in the beaker got coloured uniformly as shown in figure D.
Selina Concise Biology Class 8 ICSE Solutions – Transportation in Plants 6
Answer:
(a) Name and define the phenomenon shown in the experiment.
Answer: The phenomenon is diffusion. Diffusion is the movement of the molecules or atoms of a substance (whether in a solid, liquid or gaseous state) from the region of higher concentration to the region of lower concentration.

(b) In all the four figures, two kinds of molecules are shown symbolically – larger and smaller. Which molecules are of the solute and which are of the solvent?
(a) Larger: ………… (b) Smaller: …………..
Answer: (a) The larger molecules are of the solute (dye)
(b) The smaller molecules are of the solvent (water)

(c) If all the dark shaded molecules in A are tightly enclosed in a cell membrane, what will be the nature of movement of the molecules, if any ?
Answer: As the concentration of solvent molecules is more in the left side of the figure A. The cell membrane will act as semi permeable membrane and will allow only the solvent molecules of water to move towards the solute particles. So the solvent molecules will move towards the solute particles. This will show the phenomenon or process of osmosis.

Question 9.
Briefly explain, how transpiration helps in upward conduction of water in plants? (a) ………… (b) ……………
Answer:
(a) Plants continuously absorb water through their roots. This water is sent up through the stem to all parts of the plant, including the leaves. Only a little amount, of water is retained in the plant or utilised by it in photosynthesis. The rest of it gets evaporated into the atmosphere as water vapour through the stomata present in the epidermis of the leaves and other aerial parts of the plant. This creates a suction pressure which pulls up water from xylem of the roots to the stem and then to the leaves.

(b) Xylem tissues are in the form of capillary tubes (tracheids and fibres) where narrower the diameter, greater will be the force. Whenever the xylem vessels lay empty, such as during the loss of water by transpiration, the water from below rises into them by a capillary force.
During day time, water is lost from the surface of the leaves by the process of transpiration. In this process, more and more water molecules are pulled up due to their tendency of rentainingjoined (cohesion). Such pulling force created by the leaves is very important in the case of tall trees where an upward conduction of water takes place.

Question 10.
How does temperature, light intensity and wind affect transpiration?
Answer:
Temperature: Transpiration is faster on hot summer days as compared to cold winters.
Light intensity: The transpiration rate is increased due to the increase in light intensity. During daytime in the sunlight, the rate of transpiration is faster. This is because the stomata remain open to allow the inward diffusion of carbon dioxide for photosynthesis. During dark, the stomata are closed, and hence transpiration hardly occurs at night.
Wind: Transpiration is more when the wind is blowing faster as water evaporates faster from the leaves.

Question 11.
The set up shown alongside was kept in sunlight for an hour. It was observed that drops of water appeared on the inside of the polyethylene bag.
Selina Concise Biology Class 8 ICSE Solutions – Transportation in Plants 7
(a) Name the process which is being demonstrated.
(b) Why was the pot and its soil left uncovered by the polythene bag ?
(c) Why was the pot left in the sunlight?
(d) Suppose the pot in this experiment was placed inside a dark room instead of placing it in sunlight for some time. What difference will be noticed?
Answer:
(a) The process demonstrates the loss of water that has appeared in the polythene bag is transpiration.
As the potted plant covered with polythene bag is kept in the sunlight there will be loss of water through the stomata present on the leaves. The water drops will appear inside the polythene bag as a result of loss of water from the stomata. This is due to transpiration.

(b) As the potted plant is kept in the sun. The water vapours will also be given by the pot and the wet soil. These vapours (water drops) will also go inside the polythene if it covers the pot and the soil. We left the pot and soil uncovered by the polythene so that we may find the loss of water from the aerial parts of the plant covered with polythene bag. This shows that the water gets deposited in the polythene bag has come from the aerial parts of plant.

(c) As we keep the pot in the sunlight the stomata will open and the loss of water i.e., transpiration takes place from the aerial parts of the potted plant and the stomata. The loss of water will be more (transpiration) in the sun, and water vapours will appear in the polythene bag very soon.

(d) As we keep the pot inside the room, the stomata will not open fully and the rate of loss of water will be very-very less, and no water vapours will appear in the polythene bag. By keeping the pot in the room the loss of water will be very less and as a result the transpiration will be very less.

Question 12.
State whether the following statements are true or false. Rewrite the false statements correctly.
(a) Water absorption mainly occurs through the root-hair.
True
(b) Water enters the root-hair by osmosis.
True
(c) Water absorbed by the roots reaches the leaves and is used in producing food for the entire plant.
True
(d) A semi-permeable membrane allows larger molecules to pass through, but prevents the smaller ones.
False. A semi-permeable membrane allows smaller molecules to pass through, but prevents the smaller ones.
(e) Transpiration is the loss of water from the roots of the plant.
False. Transpiration is the loss of water from the aerial parts of the plant.
(f) Transpiration cools the plant when it is hot outside.
True
(g) During transpiration, the leaves lose more water from their upper surface.
False. During transpiration, the leaves lose more water from their lower surface.

Question 13.
Fill in the blanks with suitable terms given below: (Fast, Leaves, Stomata, Conducting, Ascent, Humid)
(a) Transportation in plants is carried out by a conducting system.
(b) The upward movement of sap that contains water and minerals is called ascent of sap.
(c) Transpiration is more when the wind is blowing fast.
(d) Most water gets evaporated from the plant from its leaves.
(e) Transpiration is reduced if the air is humid.
(f) The leaves have more stomata on their lower surface.

Long Answer Questions:

Question 1.
Draw a magnified view of the root-hair, and describe, how it helps in the absorption of water from the soil.
Answer:
Selina Concise Biology Class 8 ICSE Solutions – Transportation in Plants 8
Give above is a magnified view of a root-hair. It is a long protuberance of a cell. This cell contains a fluid called cell sap which is more concentrated than the surrounding soil water.
The root hair is covered by a very thin ceil membrane that allows water molecules to pass through, but prevents the larger molecules. So the water from the soil passes into the root hairs by osmosis.

Question PQ.
“Raisins swell in water, and grapes shrink in syrup.” Explain this phenomenon briefly.
Answer:
When we put some raisins in a bowl containing water, after 10-12 hours, we will notice that the raisins have swelled up. The raisins have absorbed water.
Selina Concise Biology Class 8 ICSE Solutions – Transportation in Plants 9
But when we put some soft-skinned grapes in another bowl containing thick syrup of sugar. After 10-12 hours we will notice that grapes have shrunk. The grapes have lost water.
Selina Concise Biology Class 8 ICSE Solutions – Transportation in Plants 10
In both cases the gain or loss of water is through the peel acting as a kind of semi-permeable membrane. This membrane has very minute pores which allow water molecules to pass through, but prevent the larger ones of sugar.

Question 2.
How does transpiration help the roots absorb water and minerals from the soil?
Answer:
Transpiration process in plants creates a suction pressure which pulls up water from xylem of the roots to the stem and then to the leaves.
Xylem tissues are in the form of capillary tubes (tracheids and fibres) where narrower the diameter, greater will be the force. Whenever the xylem vessels lay empty, such as during the loss of water by transpiration, the water from below rises into them by a capillary force.
Due to transpirational pull more and more water molecules are pulled up due to their tendency of remaining joined (cohesion). Such pulling force created by the leaves is very important in the case of tall trees where an upward conduction of water takes place.

Question 3.
Define the three processes by which plants absorb water and minerals from the soil.
Answer:
Following are the tree processes which help the plants to absorb water and minerals from the soil.

  1. Diffusion: Soil water moves into the root hairs through the process of diffusion from higher concentration to lower concentration as we put sugar in the milk and the sugar molecules are evenly distributed in the milk and occupy inter molecular spaces of milk.
  2. Osmosis: The cell sap and the cell walls act as semi- permeable membranes and permeable membranes. The concentration of the cell sap is more as compared to the water + minerals present in the soil. So the water and dissolved minerals enters the roots by the process of osmosis.
  3. Active transport: Root hairs absorb water and minerals from the soil. Water diffuses into the root hairs as the concentration of water is more as compared to root hair.
    But in case of minerals these move from lower concentration to molecules of higher concentration. So the minerals from the soil along with water move into the roots. So this is active transport in the opposite direction which needs energy.

Question 4.
How water absorbed by the roots is important for the plants?
Answer:
The water absorbed by the roots is important for the plant in three main ways:

  1. Transportation: The water in the plant body transports substances in solution from one part to another.
  2. Food production: Water is used in producing food (photosynthesis) by combining it with carbon-dioxide from the air in the presence of sunlight.
  3. Cooling: Water is used to cool the plant by evaporation through leaves when it is hot outside.

Question 5.
Name the factors which affect the rate of transpiration? State their role in each case.
Answer:
The following are the main factors that affect the rate of transpiration:

  1. Sunlight: During daytime, the rate of transpiration is faster. This is because the stomata remain open to allow the inward diffusion ofcarbondioxide for photosynthesis.
    During dark, the stomata are closed, and hence transpiration hardly occurs at night.
  2. Temperature: Transpiration is faster on hot summer days as compared to cold winter.
  3. Wind: Transpiration is more when the wind is blowing faster as water evaporates faster from the leaves.
  4. Humidity: Transpiration is reduced if the air is humid. Air cannot hold any water molecules when it is already laden with moisture (humidity).
  5. Low atmospheric pressure: The rate of transpiration increases when the pressure is low.

Question 6.
Mention the two ways in which transpiration helps the plants.
Answer:
Transpiration helps the plants in the following ways:

  1. Cooling effect: In transpiration, water gets evaporated from the plant. The heat required for this evaporation is obtained from the plant itself (latent heat) and thus the plant is able to cool itself w’hen it is hot outside.
  2. Transpiration helps in maintaining the concentration of the sap inside the plant body: The roots continue to absorb water from the soil. If excess water is not evaporated out, the sap would become dilute, preventing further absorption of water along with the minerals required by the plant.

Question 7.
Describe an experiment to show that the plant loses water through its leaves.
Answer:
Experiment: To demonstrate that the plants lose water through its leaves.

  • Take one small-sized, well-watered potted plant having a few branches. Place a polythene bag over its one branch as shown in A and tie it with a rubber band.
    Selina Concise Biology Class 8 ICSE Solutions – Transportation in Plants 11
  • Remove all the leaves from another branch (B) of the same plant, cover this too with a polythene bag and tie it with a rubber band.
  • Place the plant in sunlight, and observe it after 4-6 hours. You will notice that drops have appeared on the inner surface of the polythene bag over branch A, while no water drops appear on branch B.
  • This set-up indicates that most water gets evaporated from the plant through its leaves.

Question 8.
Name any three minerals whose deficiency causes diseases in plants. Give the symptoms of each deficiency.
Answer:
The nutrient elements i.e. minerals are essential for the plants to grow well and complete their life-cycle properly. The minerals are divided into two main categories:

(i) Macro-Nutrients: They are required in larger concentrations and they are obtained from soil.
The three macro-nutrients (minerals) whose deficiency causes diseases in plants are:

  1. Nitrogen (N) – Yellowing of leaves,wrinkling of cereal grains.
  2. Phosphorus (P) – Purple and red spots on leaves, delay in seed germination.
  3. Potassium (K) – Poor Growth

(ii) Micro Nutrients: They are required in small amounts and they are also obtained from soil.
The three micro-nutrients(minerals) whose deficiency causes diseases in plants are:

  1. Iron (Fe) – Yellowing of Leaves.
  2. Manganese (Mn) – Yellowing of leaves, with grey spots.
  3. Zinc (Zn) Desphaped leaves, yellowing of leaves, stunted plant growth.

Question 9.
List out the differences between xylem and phloem.
Answer:
The Xylem tissue consists of four types of cells:

  1. Tracheids: They are elongated dead cells with tapering ends. Their main function is in upward conduction of water and provide mechanical support.
  2. Vessels: They are like tube-like structures placed one above the other forming long channels. They provide mechanical support and also transport water and mineral salts laterally and vertically upward.
  3. Fibres: They are long, narrow and tapering at both ends. They provide only mechanical support.
  4. Parenchyma: They are living cells and helps in the conduction of water and minerals, and serve for the storage of food.

The Phloem tissue consists of four types of cells:

  1. Seive tubes: They are formed of seive cells and form the main conducting part of the phloem. These are cylindrical cells arranged in vertical rows, joined end to end. Their end walls are perforated by pores and are called seive plates. Seive piates helps in passing food material from cell to cell.
  2. Companion Cells: They are associated with seive tubes. It help sieve tubes in the conduction of food material.
  3. Parenchyma: It is formed of thin-walled unspecialized parenchymatous cells and these cells store food.
  4. Phloem fibres: They are dead sclerenchyma fibres formed of elongated cells. These provide mechanical strength.

Selina Concise Biology Class 8 ICSE Solutions – Endocrine System and Adolescence

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Selina Concise Biology Class 8 ICSE Solutions – Endocrine System and Adolescence

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 8 Biology Chapter 5 Endocrine System and Adolescence. You can download the Selina Concise Biology ICSE Solutions for Class 8 with Free PDF download option. Selina Publishers Concise Biology for Class 8 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

Selina Class 8 Biology ICSE SolutionsChemistryPhysicsMathsGeographyHistory & Civics

Selina Concise ICSE Solutions for Class 8 Biology Chapter 5 Endocrine System and Adolescence

REVIEW QUESTIONS

Multiple Choice Questions:

1. Put a tick mark (✓) against the correct alternative in the following statements:

(a) Cortisone hormone is secreted by:

  1. Medulla of adrenal
  2. Cortex of adrenal
  3. Pancreas
  4. Thyroid

(b) Which one of the following hormones stimulates the breakdown of glycogen in the liver into glucose:

  1. Insulin
  2. Adrenaline
  3. Glucagon
  4. Thyroxine

(c) Which one of the following hormones converts excess of glucose into glycogen:

  1. Glucagon
  2. Thyroxine
  3. Insulin
  4. Adrenaline

(d) Which one of the following glands is also called master gland:

  1. Pituitary gland
  2. Adrenal gland
  3. Thyroid gland
  4. Ovary

(e) The emergency hormone to face the danger or to fight is secreted by:

  1. Islets of Langerhans
  2. Adrenal cortex
  3. Pituitary
  4. Adrenal medulla

(f) Which one of the following endocrine glands produces its hormone in large quantities as a result of emotional stimulation?

  1. Thyroid
  2. Islets of Langerhans
  3. Adrenal medulla
  4. Adrenal cortex

Adrenal medulla produces its hormone in large quantities as a result of emotional stimulation.

(g) In humans, increased thyroxine production results in (tick the correct answer):

  1. Increased metabolism
  2. Decreased metabolism
  3. Dwarfism
  4. Cretinism

Short Answer Questions:

Question 1.
What is a hormone?
Answer:
The secretions of the endocrine glands are called Hormones, which are poured directly into the blood and are carried to the target organs.

Question 2.
In table given below, fill in the blanks by naming endocrine glands, the hormones they secrete, and the function they perform, in a normal person.
Answer:

S.No. Name of the gland produced Function
1. Thyroid Thyroxine Control of metabolic rate
2. Pancreas Insulin Regulation of sugar in blood.
3. Adrenal Adrenaline and cortisone Preparing the body for action
4. Pituitary (i) Growth hormone
(ii) Thyroid stimulating hormone		 (i) For growth
(ii) Stimulates thyroid gland to secrete thyroxine

Question 3.
Match the items in Column A with those in Column B. Column A Column B
Selina Concise Biology Class 8 ICSE Solutions – Endocrine System and Adolescence 1

Answer:

Selina Concise Biology Class 8 ICSE Solutions – Endocrine System and Adolescence 2

Question 4.
Name the source and the function of each of the following hormones:

Hormone Source Function
(a) Glucagon
(b) Thyroxine
(c) Adrenaline
(d) Insulin
(e) Cortisone

Answer:

Hormone Source Function
(a) Glucagon Pancreas Breakdown of glycogen to glucose. Raises sugar in the blood.
(b) Thyroxine Thyroid gland Control of metabolic rate
(c) Adrenaline Adrenal gland Prepare the body to face emergency, stress
(d) Insulin Pancreas Regulation of sugar in blood.
(e) Cortisone Adrenal cortex Regulates carbohydrate metabolism. Its deficiency causes Addison’s disease.

Question 5.
What is the difference between an exocrine gland and an endocrine gland?
Answer:
The salivary glands, pancreas, etc., are exocrine glands, they send their secretions through ducts directly to the target orgOn the other hand, the endocrine glands are ductless glands. Their secretions are called hormones, which are poured directly into the blood and are thus carried to the target organs.

Question 6.
Why is pitnitary gland is called “master gland”?
Answer:
The pituitary gland is called “master gland” because it produces hormones that control other glands and many body functions including growth (growth hormone, Thyroid and Gonad stimulating hormone).

Question 7.
Briefly write about the importance of physical hygiene during adolescence.
Answer:
Physical hygiene also named as Personal hygiene plays a crucial role in maintaining healthy during adolescence. The teenager should follow the below mentioned activities to promote their health:

  1. Proper and Safe Food: Adolescence is a stage of rapid growth and development. Hence, a teenager should take proper care of their diet. They should take proper balanced diet that provides protiens, carbohydrates, fats, minerals and vitamins. They should take freshly prepared food and avoid stale food. They should take milk, fruits and fresh vegetables.
  2. Proper life Style: Regular Exercise and sleep are necessary for maintaining good health. Teenager should avoid long hours of continous table work, television watching. Teenager should not consume alcohol, drugs or smoking.
  3. Cleanliness: Teenager should take bath regularly. They should always wash their hands before and after having meals. Brushing up teeths after every meal. They should always change and wear washed clothes especially undergarments. Regular toilet habits should be adopted for maintaining good health. Teenager must keep their feet cleaned and protected. Injuries due to bacteria like tetanus, hookworms and insects may be issued if barefoot walk is undertaken. They must wash and comb their hairs regularly. All body parts must be washed and cleaned everyday. If cleanliness is not maintained there may occur chances of catching bacterial infection. Girls should take special care of cleanliness during the time of menstrual period.
  4. Physical Exercise: Inorder to keep the body fit and healthy, teenager’s should walk, exercise and play outdoor games regularly in fresh air. Playing Outdoor games reduces the stress and strain of adolescence.

Question 8.
Briefly discuss any four activities which can be practiced to overcome stress.
Answer:
Stress is a state of mental or emotional strain and in simple terms it is called as tension.
The stress can be controlled or reduced by following the below mentioned steps:

  1. Yoga: It is a mind-body practice that combines physical poses, controlled breathing, and meditation or relaxation. Yoga helps in reducing steps by:
    (a) Increasing Flexibility
    (b) Increasing muiscle strength and tone.
    (c) Improving respiration, energy and vitality.
  2. Exercise: Exercise or Running or Jogging for 30 to 45 minutes at least three times a week reduce stress and keep’s the body much healthier.
  3. Proper sleep schedule: Improving your sleep schedule also helps in reducing the stress.
  4. Reading is a great way to calm your mind and to gain more knowledge.
  5. Practice Hobbies of your interest: One should must keep practicing their hobbies as it helps in reducing the stress. Enjoy playing guitar, paino or listening music or doing riddles.

Selina Concise Biology Class 8 ICSE Solutions – Nervous System

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Selina Concise Biology Class 8 ICSE Solutions – Nervous System

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 8 Biology Chapter 7 Nervous System. You can download the Selina Concise Biology ICSE Solutions for Class 8 with Free PDF download option. Selina Publishers Concise Biology for Class 8 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

Selina Class 8 Biology ICSE SolutionsChemistryPhysicsMathsGeographyHistory & Civics

Selina Concise ICSE Solutions for Class 8 Biology Chapter 7 Nervous System

REVIEW QUESTIONS

Multiple Choice Questions:

1. Put a tick mark (✓) against the correct alternative in the following statements:

(a) Medulla oblongata controls

  1. Smelling
  2. Beating of heart and respiratory movement
  3. Intelligence and will power
  4. Balancing the body

(b) Balance of body is controlled by:

  1. Spinal cord
  2. Cerebellum
  3. Cerebrum
  4. Medulla

(c) The smell of good food causes watering of your mouth. It is a

  1. Natural reflex
  2. Acquired relfex
  3. Inborn reflex
  4. Ordinary reflex

(d) The structural and functional unit of nervous system is a

  1. Axon
  2. Nephron
  3. Neuron
  4. Texon

Short Answer Questions:

Question 1.
Name the two types of coordination which take place in our body.
Answer:
(a) Nervous coordination: By nerves and brain
(b) Chemical coordination: By hormones

Question 2.
Your are driving your bicycle at a fast speed. Suddenly, a small boy comes in front of your cycle and, without wasting any time in thinking, you immediately apply the brakes and accident is avoided. What name is given to such an action?
Answer:
Reflex action (acquired).

Question 3.
Given below is the diagram of a neuron. Name the parts numbered 1-5.
Selina Concise Biology Class 8 ICSE Solutions – Nervous System 1
Answer:

  1. Dendrite
  2. Nucleus
  3. Cell Body (Nyton)
  4. Axon (Nerve fibre)
  5. Node of Ranvier

Question 4.
Write one word in the space provided to complete the second pair of the related words pertaining to nervous system.
Memory : cerebrum : : breathing :
Balance : cerebellum : : reasoning :
Answer:
Memory : cerebrum : : breathing: medulla oblongata
Balance : cerebellum : : reasoning : cerebrum

Question 5.
Differentiate between the following pair of terms:
(a) Stimulus and impulse
(b) Receptor and effector
(c) Motor nerve and sensory nerve
Answer:
(a) Stimulus: Any change in the environment that usually results in change in the activity of the body.
Impulse: A wave of electrical disturbance that runs through the nerves.

(b) Receptor: The nerve cell on receiving the stimulus sets up the waves of impulses towards the central nervous system.
Effector: Any muscle or gland on receiving the impulse from the brain (or the spinal cord), contracts or secretes.

(c) Motor nerve: It contains only motor neurons,
Example: Nerves going to the muscles of the eyeball.
Sensory nerve: It contains only sensoiy neurons.
Example: optic nerve of the eye.

Question 6.
(a) Name the three major divisions of the human nervous system.
(b) Name the three main parts of human brain.
Answer:
(a)

  1. The central nervous system (brain and spinal cord)
  2. The peripheral nervous system
  3. The autonomic nervous system

(b)

  1. Cerebrum
  2. Cerebellum
  3. Medulla oblongata

Question 7.
Give the function of each of the following:
(a) Olfactory nerve:
(b) Optic nerve:
(c) Facial nerve:
Answer:
(a) Olfactory nerve: The sense of smell is present in the epithelial layers of the nasal chambers. The sense of smell is carried to the brain by the olfactory nerve. They arise from the anterior ends of the olfactory lobes and are distributed to lining of nasal chambers.
(b) Optic nerve: It carries the reflection of the object from the retina to the brain. The image formed on the retina is in a reverted position and the correct picture is formed in the brain as the object is. The optic nerves arise from the side of diencephalon. They innervate the retina of the eye and are sensory in nature.
(c) Facial nerve: It carries message and all expressions of the face, mastication work alone by the teeth, movement of the neck and the activities of the salivary glands to the brain. It arises from the side of medulla. On the whole facial nerves are mixed in nature.

Long answer questions

Question 1.
With the help of a suitable diagram describe the structures of a neuron.
Answer:
Nervous system consists of special cells called nerve cells or neurons. It has a main cell body called cyton. It gives out many processes called dendrites. From it a very long process is given out. It is called axon or nerve fibre.
Selina Concise Biology Class 8 ICSE Solutions – Nervous System 2
The cell body has a nucleus. The dendrites get the message from the organs and send this message to the axon through the cell body. Then the axon sends the message to muscles to contrast or to the gland for secretion.
The neurons make contact with one another through their processes. The axon at its end branches and meets the dendrites of another neuron. The meeting point is called synapse. The message is passed on from one axon to the dendrites of another neuron. How the message goes ? It is like this:
Organ → Message goes to dnedrites → Cell body → Axon → Muscles or glands

Question 2.
Briefly describe the structure of the cerebrum in human brain and mention its functions.
Answer:
Brain consists of main three parts and lies in the cranial cavity of skull.

  1. The cerebrum
  2. The cerebellum
  3. The medulla oblongata

Cerebrum: It is very large and form two third of the whole brain. The two hemispheres are separated from each other by a deep longitudinal groove, the median fissure. The outer surface is folded with ridges and grooves. The hemispheres are hollow from inside and their walls have outer and inner portions. The outer portion has cell bodies of the neurons and it is called grey matter.
The wavery edges of the folded layer has large number of neurons to the extent of nine billion. The inner portion of the cerebrum has axons and it is called white matter.

Functions:

  1. It controls all the voluntary activities.
  2. It is the seat of intelligence, consciousness and will power.

Question 3.
Mention the three functions of spinal cord.
Answer:
Spinal cord has the following functions.

  1. It is the centre of reflex actions below the neck.
  2. It carries messages from the skin and muscles to the brain.
  3. All the stimuli and responses are passed from and to the brain through the spinal cord.

Question 4.
With the help of suitable example, describe reflex action.
Answer:
Reflex action: Reflex actions are automatic responses to stimuli. These actions are not under the control of the animal. They are of definite and mechanical type. Peripheral nervous system and spinal cord both control certain action and the brain is not in action.
Some examples of reflex actions are:

  1. Pupil becomes narrow when strong light falls on it.
  2. The aroma of the food makes the mouth watering.
  3. The hand is withdrawn as we touch the hot plate.
  4. Flow of bile from the gall bladder into the duodenum.
  5. A loud thud may lead to opening of the mouth.

In a reflex action brain is not involved, removing the hand on touching a hot plate is a reflex action. The impulse of heat goes from the hand to the spinal cord and the order is sent back to the muscles of the hand to remove the hand from the hot plate.

Question 5.
Describe three kinds of nerves, giving the example of each.
Answer:
A nerve is formed by a group of nerve fibres (axons) encased by tubular medullary sheath. The medullary sheath acts as insulation and do not allow mixing up of impulses of the neighbouring axons (nerve fibres) We have three kinds of nerves:

Selina Concise Biology Class 8 ICSE Solutions – Nervous System 3

  1. Sensory nerve: It brings impulses from sense organs as these have sensory fibres. These nerve carry the impulses from the sense organs to the brain or to the spinal cord as optic nerve of the eye.
  2. Motor nerves: These carry impulses to muscles or glands from the brain or spinal cord. These nerves have only motor fibres as nerves to the muscles of the eye ball.
  3. Mixed nerve: It has both sensory and motors fibres as nerve going to the tongue.

Question 6.
Differentiate between natural reflex and conditioned reflex. Give examples to illustrate your answer.
Answer:
Natural reflex: It is one in which no previous experience or learning is required. These reflexes are inborn i.e. inherited from the parents.
Examples are

  1. Blinking, coughing, sneezing as these are protective reflexes
  2. Salivation, swallowing, peristalsis as it provides functional efficiency.
  3. Dilation of the eyes pupil to look in the dark and vice versa. It is muscular movement.
  4. Pushing along of swallowed food through the food canal. It is muscular movement.

Conditioned Reflex: It is one which develops during lifetime due to experience or learning.
Examples are:

  1. Watering of mouth (Salvination) at the sight of a tasty food.
  2. Surfing the channels while watching the television.
  3. Typing of a keyboard of a computer.
  4. Playing a musical instrument.

Selina Concise Biology Class 8 ICSE Solutions – The Circulatory System

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Selina Concise Biology Class 8 ICSE Solutions – The Circulatory System

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 8 Biology Chapter 6 The Circulatory System. You can download the Selina Concise Biology ICSE Solutions for Class 8 with Free PDF download option. Selina Publishers Concise Biology for Class 8 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

Selina Class 8 Biology ICSE SolutionsChemistryPhysicsMathsGeographyHistory & Civics

Selina Concise ICSE Solutions for Class 8 Biology Chapter 6 The Circulatory System

REVIEW QUESTIONS

Multiple Choice Questions:

1. Put a tick mark (✓) against the correct alternative in the following statements:

(a) The only artery which carries deoxygenated blood is called,

  1. Hepatic artery
  2. Pulmonary artery
  3. Aorta
  4. Renal artery

(b) Pulmonary vein carries

  1. Oxygenated blood
  2. Deoxygenated blood
  3. Glucose-deficient blood
  4. CO2 laden blood

(c) Function of WBCs is to

  1. Transport oxygen
  2. Help in clotting of blood
  3. Provide immunity
  4. Provide storage of food.

(d) Blood Capillary is a

  1. Broad tube
  2. Artery with thick wall
  3. Vein with large lumen
  4. Narrow tube made up of endothelium only.

(e) Nucleus is absent in 

  1. RBCs
  2. WBCs
  3. All blood cells
  4. Liver cells.

(f) Sphygmomanometer measures

  1. Pulse rate
  2. Heart beat
  3. Blood pressure
  4. Brain activity

(g) The blood tastes saltish due to the presence of dissolved:

  1. Sodium chloride
  2. Potassium chloride
  3. Ammonium nitrate
  4. Sodium nitrate

Short Answer Questions:

Question 1.
1. Differentiate between the following pair of terms:
(a) Pulmonary artery and pulmonary vein.
(b) Vena cava and aorta.
(c) Platelets and WBC.
(d) RBC and WBC Ans.
Answer:
(a) Pulmonary artery and pulmonary vein.

Pulmonary artery Pulmonary vein
1. This involves circulation of blood from the heart to the lungs. 1. This involves circulation of blood to the heart from the lungs.
2. It carries deoxygenated blood. 2. It carries oxygenated blood.

(b) Vena cava and Aorta

Vena Cava Aorta
1. Vena Cava is a large vein. 1. Aorta is the large artery.
2. It carries deoxygenated blood from the upper and lower parts of the body i.e. head and shoulders. 2. It carries oxygenated blood to all parts of the body through its branches.

(c) Blood platelets and blood group.

Platelets WBC
1. These are colourless, oval or round, cytoplasmic fragments 1. WBC are colourless and lack haemoglobin, larger in quantity, and have distinct oval and lobed nucleus.
2. These play a major role in blood clotting. 2. They prevent body from disease causing germs by providing immunity
3. Their life span is 3-5 days and it is called thrombocytes. 3. Their life span is short i.e. 5 to 20 days.

(d) RBC and WBC

RBC WBC
1. They do not have nucleus at maturity. 1. They have a large characteristic nucleus.
2. They possess haemoglobin and are red. 2. They are colourless as they have no pigment.
3. They help in transport of respiratory gases. 3. They help in defence mechanism.

Question 2.
Give any three differences between an artery and a vein:
Answer:
Following are the differences between the artery and a vein:

Artery Vein
1. Arteries carry blood from the heart to various body parts. 1. Veins carry blood from different body parts to the heart.
2. These carry oxygenated blood (except the pulmonary artery). 2. These carry deoxygenated blood (except the pulmonary vein).
3. B lood flows with h igh speed and under high pressure. 3. Blood flows with low speed and under low pressure.

Question 3.
Fill in the blanks with suitable words given below:
Answer:
a. The two lower chambers of the heart are called ventricles.
b. The pulmonary artery takes the blood from the ventricles to the lungs.
c. The blood loaded with carbon dioxide from the body comes into the right auricle of the heart.
d. The oxygen-rich blood from the lungs comes into the left ventricle of the heart.
e. The oxygen-rich blood is pumped into different parts of the body through aorta.
f. The carbon dioxide loaded blood from right ventricle is pumped into the lungs through pulmonary artery.
g. The instrument used to find out the blood pressure is known as sphygmomanometer.
h. The colour of a red blood cell is due to haemoglobin.
i. The blood plasma contains a dissolved substance called fibrinogen.
j. The liquid part of coagulated blood is known as serum.

Question 4.
In which organ of our body does blood get oxygenated?
Answer:
Blood becomes oxygenated in the lungs. The oxygenated blood is returned to left verticles by the pulmonary vein.

Question 5.
Which side of the heart (left or right) contains oxygenated blood?
Answer:
The left side of the heart contains oxygenated blood.

Question 6.
What is the role of haemoglobin in the blood ?
Answer:
The haemoglobin is the respiratory pigment which is formed of the iron containing part known as haemin and protein part known as globin. It helps to transport respiratory gases (oxygen).

Question 7.
Name the disease in which the number of platelets reduces to 25,000 – 30,000 per cubic mm of blood. State its major symptoms.
Answer:
Dengue fever is one such disease in which the number of platelets get reduced to as low as 25-30 thousands per cubic mm of blood. The major symptoms of dengue are high fever, rashes or red spots on body, nausea or vomiting, pain in abdomen, back, or back of the eyes and muscles.

Long Answer Questions:

Question 1.
 Given alongside is a diagram of human heart showing its internal structures. Label the parts marked 1 to 6, and answer the following questions.
Selina Concise Biology Class 8 ICSE Solutions – The Circulatory System 1
(a) Which type of blood is carried by the blood vessel marked 2?
(b) Name the main artery which takes the blood from heart to different parts of the body?
(c) Which chamber of the heart receives deoxygenated blood from the body?
Answer:

  1. Left pulmonary artery
  2. Superior vena cava
  3. Left pulmonary vein
  4. Right auricle
  5. Left auricle
  6. Left ventricle

(a) Deoxygentated blood.
(b) Aortic arch (Aorta).
(c) Right Atrium

Question 2.
You can see some blood vessels on the outside of the hands specially in older people. Are those veins or arteries ? How can you confirm your answer ?
Answer:
In older persons the skin becomes loose as the fat below becomes less with age and the vessels passing through these areas especially on the outside of the hands become prominent. These are veins as they flow superficially. The veins are thin and less muscular. These carry the blood to the heart veins are placed superficially so they are easily visible to the eye and are prominent.
The blood in the veins will be carrying CO2 and will have many substances like sugar, amino acids, chemicals and bacteria.

Question 3.
Give the functions of lymph. Differentiate between Blood and the lymph.
Answer:
Functions of lymph are:

  1. Nutritive: It supplies nutrition and oxygen to those parts where blood cannot reach.
  2. Drainage: It drains away excess tissue fluid and metabolites and returns proteins to the blood from tissue spaces.
  3. Absorption: It absorbs the fats from the intestine through lymphatics.
  4. Defence: Lymphocytes and monocytes of the lymph function to protect the body. The lymphatics also remove bacteria from the tissues.

Difference between Blood and Lymph

Lymph Blood
1. It contains blood plasma without blood proteins and some RBC. 1. It contains blood plasms with proteins and all three types of blood cells namely RBC, WBC and blood platelets.
2. They are light yellow in colour and does not contain RBC and haemoglobin. 2. They are red in colour due to presence of haemoglobin in RBC,
3. It doesnot carry Oxygen. 3. It carries oxygen in the body.
4. It is the part of open circulatory system. 4. It is the part of closed circulatory system.

Question 4.
Name any two heart conditions that occur commonly. Briefly explain each of them.
Answer:

  1. Palpitations: Sometimes, one may experience the heart beating too hard or too fast or sometimes even skipping a beat. This can be frightening, but not serious or harmful and often this condition goes away on its own. Most of the time it is caused by stress or anxiety. Sometimes certain types of food may also cause palpitations.
    In rare cases, palpitations may be an indication of a more serious heart condition, specially if it is accompanied by shortness of breath, dizziness or chest pain.
  2. Hypertension: This is a condition that occurs in a person when blood flows through the blood vessels with a force greater than normal. This is also called High Blood Pressure. Hypertension can strain the heart, damage blood vessels and increase the risk of a heart attack or stroke.

Question 5.
During surgical operations or during accidents, the patient may be given blood from outside to save his life. What is the technical name of this process ? Briefly explain the precautions to be observed and taken in this process.
Answer:
During surgical operation or an accident when excess of bleeding takes place, the patient may be given blood from outside to save his life.
The transfer of blood from the donor to the recipient is called blood transfusion.
The following precautions are taken before the blood is given to the needy person:

  1. Matching of the donor’s blood with that of the recipient should be done.
  2. It should be made sure clinically that blood of donor is free from any infection.
  3. Sterilization of all the instruments to be used during the operation is must.

Question 6.
State briefly, the difference between white blood cells and the red blood cells.
Answer:
Difference between white blood cells and the red blood cells:

RBC WBC
1. They do not have nucleus at maturity. 1. They have a large characteristic nucleus.
2. They possess haemoglobin and are red. 2. They are colourless as they have no pigment.
3. They help in transport of respiratory gases. 3. They help in defence mechanism.
4. Life span is 120 days. 4. WBC have a short life span of 5 to 20 days.
5. They are about 5 million/mm3 of blood. 5. They are about 7000/ mm3 of blood.
6. In the embryonic stage the RBC are formed in the liver and spleen. But after birth, they are formed in the red bone marrow. 6. WBC are formed in the red bone marrow.

Question 7.
Answer very briefly, the following:
(a) Red Blood cells have no nucleus, then why do we call them cells?
(b) Why is it necessary to know The blood groups of the donor as well as the recipient ?
(c) Why should the blood going away from the stomach and intestines pass through the liver and not directly to heart?
Answer:
(a) RBC are formed in the liver and spleen when the organisjn is foetus. After birth these are formed in the red bone marrow. At the time of formation of RBC’s they have nucleus but later on they loose nucleus. Those enucleated cells perform all the functions of a cell so these are called cells.
RBC’s are surrounded by semipermeable plasma membrane. It contains homogenous cytoplasm and it is without the nucleus, endoplasmic reticulum, mitochondria, ribosomes and centrioles. RBC’s get advantage due to this condition. Corpuscles have more space to hold haemoglobin. It can as well give more oxygen by the haemoglobin to the tissue cells. So the enucleated condition is more useful to the tissue cells. The necessity of work has made them without nucleus and perform all the functions of the cells so they are called cells.

(b) Before transfusion of blood, it is most essential to determine the blood group of the donor and the recipient. The blood group of the donor and the recipient must match with each other, otherwise the RBC’s will stick to each other and thus the life of a recipient may be in danger as the blood groups are different. The sticking is due to the antigens (proteins) found in the blood of the donor and the antibodies found in the blood of the recipient.

(c) The blood from the stomach and the intestine goes to liver before going to the heart. Liver monitors the substances before passing into the body. Excess of glucose is retained by the liver in the form of glycogen and the excess amino acids are broken down by the liver. Harmful chemicals are detoxified and bacteria are destroyed and excess minerals, water and vitamins are stored in the liver.

Question 8.
Name the three kinds of blood vessels found in human beings. With the help of suitable diagrams, differentiate between them.
Answer:
The three kind of blood vessels found in human beings are arteries, veins and capillaries.

  1. Arteries are the blood vessels that carry blood from the heart to the various parts of the body.
  2. Veins are the blood vessels that carry blood from the body parts to the heart.
  3. Capillaries: These are the terminal branches of an artery, which rejoin to form a vein. A capillary is a very narrow tube whose walls have a single layer of cells with no muscles. Although the wall of a capillary is veiy thin, yet an exchange of nutrients, waste products and gases take place between the blood and the body fluids.Selina Concise Biology Class 8 ICSE Solutions – The Circulatory System 2

Differences:

Arteries

  1. Carry blood away from the heart.
  2. Have thick and more muscular walls.
  3. Carry oxygenated blood (except pulmonary artery which carries deoxygenated blood).
  4. The blood flows with jerks and under great force.

Veins

  1. Carry blood towards the heart.
  2. Have thin and less muscular walls.
  3. Carry deoxygenated blood (except pulmonary vein which carries oxygenated blood).
  4. The blood flows smoothly and under little pressure.

Capillaries:

  1. Arteries after entering an organ divide into number of smaller branches called arterioles which further divide repeatedly to form a network of fine branches called capillaries.
  2. The walls of the capillaries are very thin and are one cell deep.
  3. The Capillaries after the metabolic exchange unite to form larger vessels called venules, which again unite to form a vein.