Class- 7th

(Term- II)

Notes

And

Answer key

Of

All Subjects

(Part 1)

Answer key of

English 1

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English 2

Answer key of

Punjabi

Answer key of

Hindi

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Mathematics

Answer key of

History/Civics

Answer key of

Geography

VII (GEO) RAMIT KUMAR SHARMA

EXERCISE ANSWER KEY

CH – 2 ATMOSPHERE

1. Fill in the blanks.

a) Ultraviolet radiation.

b) Human activates.

c) Sink.

d) 1991.

e) Stratosphere.

f) Aerosol.

2. Give one word answer.

a) CFC.

b) Exosphere.

c) Global warming.

d) Ozone / O3.

3. Answer the following questions.

I. The main effects of climate change are :- a) Rise in the sea level due to melting of the

glaciers. b) Submerging of coastal areas by rise in the sea level. c) Intensity of the heat

wave will increase. d) Heavy floods and droughts. e) Destruction of the ecosystem.

II. Trapping of the heat in the earth’s atmosphere by the green houses like CFC and Carbon dioxide is called green house effect. Due to human activities, the amount of green houses

increase in the atmosphere. Increased amount of green house gases trap excessive heat in

the atmosphere, which lead to global warming.

III. The major green house gasses and their sources are :- a) CFCs come from aerosols, old

ACs & refrigerators. b) Methane from wetlands and livestock. c) Nitrous oxide from

biomass burning. d) Carbon-dioxide by various human activities.

IV. 1) Due to global warming bacteria can survive for longer duration and able to spread more

diseases. 2) Global warming destroys our ecosystem; it may affect the supplies of the

fresh water, clean air and food resources. It may cause more spread of diseases. 3)

Climate change is disrupting natural ecosystems in a way that is making life better for

infectious diseases 4) Humans are also at direct and dramatic risk from such insect-borne

diseases as malaria, dengue and yellow fever, spread more in warmer climate.

V. Ozone gas has its largest concentration in the Stratosphere. It has 90% of the total ozone,

thus this region is called ozonosphere. The main causes of ozone depletion are:- 1)

Deforestation and burning of forest. 2) Emission of green house gases due to burning of

fossil fuels. 3) Use of aerosols, refrigerators and air conditioners, which release harmful

CFCs in the atmosphere. 4) Global warming. 5) Overuse of chemical fertilizers.

VI. The ozone layer lies in the stratosphere is very important gas. It does not allow the

harmful Ultraviolet radiation of the sun to pass through it and reach on the earth surface.

In this way ozone layer protect us from harmful UV rays of the sun and make life possible

on the earth surface.

VII. CFCs are totally man-made harmful green house gases. This gas is causing global warming

and ozone depletion. The various sources of CFCs are:- 1) Aerosol. 2) Old refrigerators and

air conditioners. 3) Plastic containing harmful chemicals.

VIII. The main steps taken for the mitigation of the problem are:- 1) The United Nations

Framework convention on climate change (UNFCCC) sets an overall framework for all the

countries. In this convention, it was agreed that all countries work to reduce global

warming below20𝑐. 2) Rio earth summit in 1992, where 154 nations agreed to prevent

harmful effects of the pollution. 3) The Kyoto Protocol, where countries agreed to cut the

green house gas emissions by 5.4% 4) The Global Environmental Facility was set up in

1991 to increase cooperation on conservation of environment.

IX. The main objectives of the GEF are :- a) Reduction of the green house effect in the

atmosphere. b) Protection of the biological diversity. c) Protection of international waters.

d) Reduction of ozone layer depletion.

X. The main effects of the global warming on the flora and fauna are:- 1) Due to warmer

temperature plants and animals move to higher elevations and latitudes to survive. 2) We

lose many species and endangerment rise along with global temperature. 3) 30% of our

plants and animals are at risk of extinction by 2050. 4) Plants and animals also lose their

natural habitat through desertification and deforestation due to global warming. 5)

Destruction of the natural ecosystem.

XI. The major gas released from the use of fertilizer is Nitrous oxide. It is an important green

house gas. The increasing amount of Nitrous oxide leads to global warming.

XII. The main effects of the ozone depletion are :- 1) More amount of harmful UV rays reach

on the earth surface. 2) Skin cancer. 3) More exposure for infectious diseases. 4)

Reduction of planktons may kill fishes.

XIII. The ways to control global warming are:- 1) conservation of forest by stopping

deforestation, reforestation and afforestation etc. 2) Reduction of industrial pollution by

strict law and regulation. 3) Use less fossil fuel and encourage the use of non-renewable

sources of energy like:- wind, solar and tidal energy. 4) Use less CFCs. 5) Encourage the

use of public transport instead of private vehicle. 6) International cooperation for

environmental conservation and sustainable growth.

XIV. The ways to prevent ozone layer are:- 1) Encourage the use of public transport instead of

private vehicle. 2) Stop the use of CFCs and encourage the use of eco-friendly products. 3)

Control over use of chemical fertilizer and pesticides. 4) Ban the use of Nitrous oxide. 5)

Reduce global warming and environmental pollution.

4. Extra question

Q1. What do you mean by atmosphere?

Ans:- The layers of gases surrounding the earth is called atmosphere. In simple words we

can say that all the air around us is called atmosphere.

Q2. What do you mean by atmospheric pressure?

And:- The pressure exerted by the weight of the air is called atmospheric pressure.

Q3. Give an average atmospheric pressure at the sea level?

And:- 1.03 kg/ per cm sq.

Q4. Name the factors affecting atmospheric pressure.

And:- The main factors affecting atmospheric pressure are:- a) Altitude

b) Temperature & c) Water Vapours.

Q5. What are main layers of atmosphere?

Ans:- The main five layers of atmosphere:- Troposphere, Stratosphere, Mesosphere,

Thermosphere & Exosphere.

Q6. Describe the composition of atmosphere.

Ans:- Our atmosphere is made up of various gases like Nitrogen 78%, Oxygen 21% and 1%

other gases like Argon, Carbon-dioxide, Hydrogen and Helium etc. It also contains

particles like Dust particles, Smoke particles, Pollution particles, pollen and Salt particles

etc.

Q7. What do you mean by word Troposphere?

Ans:- The word Troposphere means turbulence.

Q8. Name the layer which protects us from meteor.

Ans:- Mesosphere protect us from meteors.

Q9. What do you know about ozonosphere?

Ans:- Lower part of the stratosphere, which has 90% ozone of the total atmosphere is

called ozonosphere. This layer protects us from harmful uv rays of the sun.

Q10. Which layer is also known as Ionosphere & why?

Ans:- Thermosphere is also known as Ionosphere, because it has presence of some

electrically charged particles called ions.

Q11. Give some important features of exosphere.

Ans :- The main features of exosphere are:- 1) It extends upto 10000km above the earth

surface. 2) It has lowest density of air. 3) The main gases here are hydrogen and helium.

Q12. Distinguish between Troposphere & Stratosphere.

Ans:- 1)Troposphere is lowest layer/stratosphere is 2nd layer above which lies above

troposphere.

2) Troposphere lies up to avg 14 km above the earth surface/ Stratosphere lies upto 50km

above the earth surface.

Q13. Give any one importance of ionosphere.

Ans:- Ionosphere helps us in shortwave radio communication.

*****************

Answer key of

Physics

st.joseph’s convent school,Moga

Answer key(2nd term)

Class-7th

subject-Physics

Answer key of

Chemistry

St. Joseph’s Convent School , Moga

CLASS-VII SUBJECT- CHEMISTRY

CHAPTER – 4

Atoms, Molecules and Radicals

[Note: Complete your notebook neatly. There will be marks deduction

for bad handwriting.]

Short-Answer Questions:

1.Define atom and molecule.

Ans. Atom: It is the smallest part of an element that can take part in a

chemical reaction.

Molecule: It is the smallest part of an element or a compound that is

capable of existing independently.

2. What do you mean by the atomicity of an element?

Ans. The number of atoms contained in a molecule of an element or a

compound is known as its atomicity.

3. What are the atomicities of neon, oxygen, ozone, phosphorus and

sulphur ?

Ans. Name Atomicity

Neon 1 (Monoatomic)

Oxygen 2 (Diatomic)

Ozone 3 (Triatomic)

Phosphorus 4 (Tetraatomic)

Sulphur 8 (Octaatomic)

4. What do you mean by the valency of an element? How is it

expressed? Name two divalent elements.

Ans. The combining capacity of an element with other elements is

known as its valency.

The valency of an element is given by the number of hydrogen atoms

that combine with one atom of the element. It is also given by the

number of hydrogen atoms that an atom of an element replaces in a

compound.

Name of the two divalent elements are Oxygen and Magnesium.

5. What do you mean by the groups and periods of the periodic table?

Ans. A group is a vertical column of the periodic table. There are 18

groups in a periodic table.

A period is a horizontal row of the periodic table. There are 7 periods in

a periodic table.

6. What is the correlation between the valency of an element and its

position in the periodic table?

Ans. Valency is an important property of an element. If you know the

number of group to which an element belongs, you will be able to

guess the valency of that element. Like elements of groups 1,2,13 and

14 have valencies 1,2,3 and 4 and those of groups 15,16,17 and 18 have

the valencies 3,2,1 and 0 respectively.

Long-answer questions:

1.Discuss how atoms, molecules and radicals differ from each other.

Give examples.

Ans.

Example of atom: hydrogen (H)

Example of molecule: water (H2O)

Example of radical: sulphate (SO42-)

2. Describe, giving three examples, how atoms form molecules.

Ans. When an atom of an element combines with another atom(s) of

same element, a molecule of the element is formed. When atoms of

two or more elements combine, a molecule of a compound is formed.

For example, (i) Two atoms of hydrogen combine to form a molecule of

hydrogen element (H2).

(ii) Two atoms of hydrogen combine with one atom of oxygen to form a

molecule of water (H2O).

(iii) One atom of carbon combines with two atoms of oxygen to form a

molecule of carbon dioxide (CO2).

3. Can the valency of an element be variable? If it can, mention two

such elements and show how they form compounds. How are these

compounds named?

Ans. Yes, valency of an element can be variable.

Two such elements are: Iron and Copper.

These elements combine with other atoms by donating, accepting or

sharing electrons in different proportions depending on nature of the

reaction. Like, iron forms FeCl2 as well as FeCl3 . Iron shows valency 2 in

FeCl2 and valency 3 in FeCl3 . FeCl2 is named as iron(II) chloride and

FeCl3 is named as iron(III) chloride.

Chapter-5

Language of Chemistry

Short-answer questions:

1.What do you mean by a reactant and a product?

Ans. Reactant: The substance which participates in a chemical reaction

is called reactant.

Product: The substance which is formed by chemical reaction between

reactants is called product.

Reactants → Products

2. What happens to the atoms in a chemical reaction? Explain with an

example.

Ans. Atoms rearrange themselves during a chemical reaction.

For example, during the burning of coal, the carbon of coal combines

with oxygen of air to form carbon dioxide. The atoms of carbon and

molecules of oxygen rearrange themselves to form carbon dioxide.

3. Why are chemical reactions accompanied by energy change?

Ans. A chemical reaction involves change in energy due to breaking or

formation of bonds during chemical reaction.

4. What are exothermic reactions? Give an example.

Ans. A reaction in which heat is released is called exothermic reaction.

For example,

Carbon + oxygen burn carbon dioxide

5. What are endothermic reactions? Give an example.

Ans. A reaction in which heat is absorbed is called endothermic

reaction.

Nitrogen + oxygen electric spark nitric oxide

6. What is that substance called which generally speeds up a reaction,

but itself remains unchanged? Give an example of such a substance.

Ans. That substance is called catalyst. Example: Manganese dioxide

(MnO2).

7. What is effervescence? Give an example.

Ans. When gas bubbles are formed, usually with a hissing sound due to

a reaction, the phenomenon is called effervescence.

For example,

Sodium carbonate + hydrochloric acid (dil.) sodium chloride +

water + carbon dioxide (g)

8. What is precipitate? Give an example.

Ans. A precipitate is a solid that separates when a solution is added to

another. For example,

Lead acetate + potassium iodide lead iodide + potassium acetate

9. Give word equations to represent the following chemical reactions.

(a) Copper(II) sulphate pentahydrate loses all its water at 260 ◦c.

(b) Sodium carbonate reacts with dilute hydrochloric acid to form

sodium chloride, water and carbon dioxide.

Ans. (a)

Copper(II) sulphate pentahydrate 260 ◦c copper(II) sulphate + water

(b)

Sodium carbonate + hydrochloric acid (dil.) sodium chloride +

water + carbon dioxide (g)

Long-answer questions:

1.Write a note on energy changes in a chemical reaction.

Ans. When a chemical reaction occurs, bonds in the reactants break

while new bonds form in the product. It involves change in energy.

Overall reaction either releases or absorbs energy. A reaction in which

heat is absorbed is called endothermic reaction. A reaction in which

heat is released is called exothermic reaction.

2. Show, giving examples, how you can make chemical equations

more informative.

Ans. Chemical equations can be more informative using following ways:

1.By mentioning the conditions of a reaction on the arrow in the

equation e.g.,

Hydrogen peroxide manganese dioxide water + oxygen

Calcium carbonate 900 ◦c calcium oxide + carbon dioxide

2. By mentioning colours and states of reactants and products within

small brackets below their names e.g.,

Copper(II) carbonate heat copper(II) oxide + carbon dioxide

(green) (black)

Hydrogen + oxygen water

(gas) (gas) (liquid when cooled)

3. By indicating a gaseous product by an upward arrow and a

precipitate by a downward arrow:

Iron + sulphuric acid (dil.) iron(II) sulphate + hydrogen

Lead acetate + potassium iodide lead iodide + potassium acetate

Answer key of

Biology

St. Joseph’s Convent School, Moga

Class:- VII

Subject:- Biology

Chapter No:- 4 PHOTOSYNTHESIS

D. Answer the followings:

1. Why is glucose converted into starts immediately after its formation in the cells?

Ans: Glucose is converted into starch immediately after its formation in the cells because starch is a

condensed form carbohydrate which takes less space for storage. Also, accumulation of glucose in the

cells will slow down the rate of photosynthesis.

2. Too much bright light and high temperature above 45 degree Celsius slow down photosynthesis.

why?

Ans: Too much light bright destroys chlorophyll and at high temperature above 40 degree Celsius the

enzymes get denatured. As a result the rate of photosynthesis slows down.

3. What is the role of carbon dioxide and water in the process of photosynthesis?

Ans: In the process of photosynthesis water molecules break into H+ and OH- ions by using the energy of

the sun. The OH- ions release oxygen into the air, whereas H+ ions combined with carbon dioxide and

form glucose. Thus, during photosynthesis water releases Oxygen and Carbon dioxide take part in the

formation of glucose.

4. How do chlorophyll and sunlight effect photosynthesis?

Ans: Chlorophyll absorbs light energy from the sun, which is essential for photosynthesis.

Photosynthesis does not occur in the absence of chlorophyll or sunlight.

Sunlight provides energy for photosynthesis. Light of low intensity Slow down photosynthesis whereas

too much bright light destroy chlorophyll and thus, hamper photosynthesis.

5. Why are green plants called autotrophs?

Ans:- Green plants are called autotrophs because they can make their food using raw materials by the

process of photosynthesis.

6. What does photo represents in term photosynthesis ?

Ans:- The ‘photo’ in term photosynthesis represents ‘light’ because green plants synthesise food in the

presence of Sunlight.

7. Name the raw materials needed for photosynthesis ?

Ans: carbon dioxide, water, chlorophyll and sunlight are the raw materials needed for photosynthesis.

8. Write equation to represent the basics of photosynthesis.

Ans:

9. Which form of energy is utilised by chlorophyll? In which form is this energy converted during

photosynthesis and stored in glucose?

Ans: Light energy is utilised by chlorophyll. The light energy is converted into chemical energy during

photosynthesis and stored in glucose.

H. Diagram Based Questions.

3 . Observe the experimental set-up and answer the following questions:

(a) Why is an aquatic plant used in the experiment

Ans: Release of oxygen during photosynthesis can be demonstrated in the form of bubbles in water

only. Therefore aquatic plants like hydrilla is used in the experiment.

(b) Why have these Bubbles appear in the setup.

Ans: These bubbles have appeared as a result of photosynthesis due to generation of oxygen.

(c) How is this gas evolved? Give the reaction.

Ans: Oxygen is evolved due to splitting of water by the Solar Energy trapped by chlorophyll as

follows.

THINK ZONE

Why do the leaves of a plant kept in dark become yellow ?

Ans: In the absence of Sunlight chloroplasts start changing their form giving yellow

colour to the leaves. Therefore, leaves become yellow when plant is kept in dark.

Photosynthesis slow down above 40 degree Celsius. Why?

Ans: Photosynthesis slows down above 40 degree Celsius because at high temperature,

i.e.40 degree Celsius or above the enzymes required for photosynthesis get destroyed.

The end product of photosynthesis is glucose then why we should we say starch is

formed during photosynthesis.

Ans: We say starch is formed during photosynthesis because some glucose is converted

into starch immediately after its formation in cells and is taken to parts of the plant for

storage.

Chapter 3 Kingdom Animalia

CHECK POINT-1

1. Invertebrates 2. Poriferans or sponges

3. Flatworms or Platyhelminths 4. Insects 5. Nephridia.

CHECK POINT- 2 1.True 2.False 3.False

TEST YOURSELF

A. Fill in the blanks:-

1 . Molluscs 2. Arthropods 3.Myriapods 4.Amphibians 5. Mammals

B. Give one word for each of the following.

. 1.Coelenterates 2.Insects 3.Invertebrates 4.Amphibians

C. Differentiate between the following.

D. Answer these questions.

1. Name different classes of vertebrate animals with one example of each.

Ans: . Different classes of vertebrate animals are :

a) Pisces(fishes)- Catla

b) Amphibia - frog

c) Reptilia snake

d) Aves-pigeon

e) mammalia-giraffe.

2. How are fishes different from amphibians?

Ans: (1) Fishes live in water and have fins for swimming whereas amphibians live on land as

well as in water. They have two pairs of limbs for locomotion on land.

(2) Fishes breathe through gills and take oxygen dissolved in water. Amphibians breathe

through lungs when on land but through moist skin when in water

3. Give two main features of mammals?

Ans: Two features of mammals.

(1)mammals have hairs on their body.

(2)The females have mammary glands to nourish their young ones.

4. Write short notes on:

(A) Flatworms: Flatworms are the animals which have thin, soft and flattened body. They

are without body cavity. Their body is divided into many segments. They mostly live as

parasites inside the bodies of other animals which are called their hosts. Example

Liverfluke, Planaria and Tapeworm.

(B) Arthropods: Arthropods are the animals which have body divided into head, thorax and

abdomen. It is covered by a hard covering of exoskeleton. They have paired and jointed

legs. Examples: Prawn, cockroach, spider, centipede, millipede etc

(C) Reptiles: reptiles are mainly land vertebrates. Their skin is dry and covered with scales.

They have two pairs of limbs. Each Limb has five digits with claws. They breathe through

lungs. They have three chambered heart. Examples: snake, crocodile, lizards and

tortoise.

(D) Mammals: Mammals have their body covered with hairs. They have external ears and

two pairs of limbs their heart is four chambered the female give birth to young ones and

have mammary glands to nourish them. Example giraffe elephant Kangaroo, tiger cow

horse dog camel monkey and human beings.

E. Match the columns.

F. 1. (b) 2. (e) 3. (a) 4. (c) 5 (d). F.1.

G. True/False

a) False, roundworm and earthworm belong to different groups

b) True

c) False, sponge is an example of pore bearing animals

d) True

e) True

f) False, starfish is an invertebrate.

H. Encircle odd one out.

a) Bacteria: Bacteria are grouped with plants while others are animals

b) Snake: Snake is a reptile while the rest are mammals

c) Frog: Frog is an amphibian while rest are birds

d) Salamander: salamander is an amphibian while rest are fishes

e) Spider: Spider is an arachnid while rest are insects.

I. Give reason for the following.

1. whales and dolphins are grouped with mammals because they have mammary glands to

Nourish their young ones they give birth to young ones they have lungs for respiration their

heart is four chambered.

2. Female Kangaroo give birth to a premature young one. It cannot survive outside so female

Kangaroo keep it in a pouch called the marsupium this pouch has mammary glands and the

young one is fed there.

3. The borrowing and soil feeding habits of earthworms make the soil porous which increases

aeration and quick absorption of water this makes the soil fertile due to this fact earthworms

are called the farmers friends.

J. Multiple choice questions.

1.(d) 2. (c) 3. (d) 4. (b) 5. (d) 6.(a)

K. Think zone

1. The streamlined body of fish offers least resistance while swimming this is an aquatic

adaptation.

2. Worms crawl on the surface of ground with the help of a special feature called parapodia or

setae.

3. Whales are placed in class mammalia because they gave birth to young ones and have

mammary glands to nourish them.

4. The four chambered heart in birds and mammals separates impure and pure blood in right

half and left half respectively. This prevents the mixing of impure and pure blood as a result

body cells receive more Oxygen and release more energy.

Answer key of

Computer

ANSWER KEY STD.VII SUB.COMPUTER

F

b

C

F