CBSE 7th Standard Science Physical and Chemical Changes Model Questions Papers Study Material - QB365 Set B | QB365

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CBSE 7th Standard Science Physical and Chemical Changes Model Questions Papers Study Material - QB365 Set B

Published on: 31/10/2025

Question Set B

CBSE 7th Standard Science Physical and Chemical Changes Model Questions Papers Study Material - QB365

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Std: 7th Standard CBSE - Science

chapter: Physical and Chemical Changes - Model Questions Papers

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Questions:

Generic 3

3 x 3 = 9

Sonu's mother served a glass of hot milk before going to school. As Sonu was in a hurry he forgot to drink the same. Unfortunately, his mother also had gone out. When they came back home, Sonu noticed the changes arose in the milk, which was no more milk, but set into a thick substance known as curd.
Based on this situation answer the following questions:
(i) What is this process of setting milk into curd known as? Is this a physical/chemical change?
(ii) Is this change harmful?
(iii) How does it happen?
(iv) Which value Sonu exhibit her

When a candle burns, both physical and chemical changes take place. Identify these changes. Give another example of the familiar process in which both the chemical and physical changes take place.

When baking soda is mixed with lemon juice, bubbles are formed with the evolution of a gas. What type of change is it? Explain.

Generic 2

3 x 2 = 6

Give four characteristics of a physical change

Is souring of milk a physical change or a chemical change? Why?

How can you say that ripening of a fruit is a chemical change?

Generic 5

2 x 5 = 10

If you leave a piece of iron in the open for a few days, it acquires a film of brownish substance, called rust.
(a) Do you think rust is different from iron?
(b) Can you change rust back into iron by some simple method?
(c) Do you think the formation of rust on iron is a chemical change?
(d) Give two other examples of a similar type of change.

In the summer holidays, Karan went to Rann of Kutch in Gujarat with his parents. Karan was aware that in the coastal regions of India especially in the Rann of Kutch common salt is obtained from seawater. Karan was very excited to see that place. He requested his father that he wants to see the process of obtaining salt from the sea. His father helped him and they went to see the place where common salt was collecting. And he also explained the whole process. Karan was very happy to see the process. Now, answer the following questions.
(a) How is common salt obtained from sea water?
(b) Name the process by which salt is collected from seawater
(c) What values are shown by Karan?

Multiple Choice Question

5 x 1 = 5

Which one is a physical change?

(a)

Melting of ice

(b)

Melting of wax

(c)

Formation of steam from water

(d)

All of these

10.

Which method is used to prevent rusting?

(a)

Galvanisation

(b)

Crystallisation

(c)

Sedimentation

(d)

None of these

11.

Two drops of dilute sulphuric acid were added to 1g of copper sulphate powder and then small amount of hot water was added to dissolve it (Step I). On cooling, beautiful blue coloured crystals got separated (Step II). Step I and Step II are

(a)

physical and chemical changes respectively

(b)

chemical and physical changes respectively

(c)

both physical change

(d)

both chemical Change

12.

Which of the following statements is incorrect for a chemical reaction?

(a)

Heat may be given out but never absorbed

(b)

Sound may be produced

(c)

A colour change may take place

(d)

A gas may be evolved

13.

A man painted his main gate made up of iron, to

(a)

(i) and (ii)

(b)

(ii) and (iii)

(c)

Only (ii)

(d)

(i) and (iii)

Fill up / 1 Marks

5 x 1 = 5

14.

A reversible change is a__________ change

15.

Oxygen and _____________are must for rusting

16.

Grinding of wheat grain changes its size. It is a __________ change

17.

A physical change is generally _________

18.

Making sugar solution is a _________ change.

True or False

5 x 1 = 5

19.

A blue deposit is formed on an iron nail when dipped in copper sulphate solution.

(a)

True

(b)

False

20.

Within our bodies, food is digested due to chemical reaction.

(a)

False

(b)

True

21.

Stretching of rubber band is not a physical change.

(a)

True

(b)

False

22.

Ships suffer a lot of damage though they are painted.

(a)

False

(b)

True

23.

Anaerobic bacteria digest animal wastes and produce biogas.

(a)

False

(b)

True

Match the following

5 x 1 = 5

24.

Chemical change

25.

Water to steam

26.

Lime stone

27.

Souring of milk

28.

Large crystals

1 Marks

5 x 1 = 5

29.

What is galvanisation?

30.

What kind of change take place when iron reacts with copper sulphate?

31.

What kind of change is rusting?

32.

Does the mixture turn blue litmus red?

33.

Does it get back its Original colour?

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Answers Key:

Generic 3

3 x 3 = 9

(i) Curdling of milk, chemical change.
(ii) This change is done by Lactobacillus bacteria and it is beneficial/useful for us.
(iii) By converting lactose sugar into lactic acid.
(iv) Irresponsibility, carelessness

Physical Changes in burning candle On heating, candle's wax melts, it is a physical change. Since it again turns into solid wax on cooling hence, the change is reversible.
Chemical changes in burning candle The wax near to flame burns and gives new substances like carbon dioxide, carbon soot. water vapours, heat and light.
Cooking of food, boiling of eggs are examples of both physical and chemical changes. In both cases, the physical appearance of the substances change and new substances are formed.

When baking soda (sodium bicarbonate) is mixed with lemon juice (citric acid), a chemical change occurs. In this reaction, new substances like carbon dioxide is formed and heat is evolved. This change is irreversible. It is a chemical change.
Sodium bicarbonate (NaHCO₃)+ Citric acid \(\longrightarrow\) Sodium citrate + Carbon dioxide\(\uparrow\) + Water + Heat

Generic 2

3 x 2 = 6

Characteristics of a physical change:
(i) It is reversible or irreversible
(ii) No new substance is formed.
(iii) No change in chemical properties.
(iv) Only change in shape, size, colour or state.

Souring of milk is a chemical change because original substances present in milk lose their nature and identity and form new chemical substances.

Ripening of a fruit is a chemical change because after ripening, a new product with different properties is formed.

Generic 5

2 x 5 = 10

(a) Yes, rust is iron oxide (Fe₂O₃). Thus, rust and iron are not the same substance.
(b) No, rusting of iron is a chemical change because in this reaction, a new substance, rust (iron oxide) is formed. It cannot be reversed by any method.
(c) Yes, rusting of iron is a chemical change. During the rusting of iron, it combines with the oxygen in the presence of water (moisture) to form a new compound 'iron oxide'. This iron oxide is a rust.
Iron + Oxygen + Water \(\longrightarrow\) Iron oxide
(From damp air) (Rust)
It is a permanent change which cannot be reversed back. So, rusting of iron is a chemical change.
(d) Two other examples are
(i) Setting of curd from milk.
(ii) Burning of magnesium ribbon to form magnesium oxide.

(a) Seawater is collected in shallow pits. It is then allowed to evaporate in the sun. As the water evaporates, the salt solution becomes supersaturated (concentrated). This supersaturated solution cannot hold the excess salt. Thus, it separates out in the form of salt crystals. These salt crystals are collected and are redissolved in water and filtered to remove insoluble impurities. The clear solution is again evaporated to obtain the crystals of pure salt.
(b) Salt is obtained from sea water by the process of evaporation.
(c) The values shown by Karan are curious, aware and intelligence

Multiple Choice Question

5 x 1 = 5