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

1

(a)

(i) and (ii)

(b)

(ii) and (iii)

(c)

Only (ii)

(d)

(i) and (iii)

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

1

(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

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

1

(a)

physical and chemical changes respectively

(b)

chemical and physical changes respectively

(c)

both physical change

(d)

both chemical Change

Which method is used to prevent rusting?

1

(a)

Galvanisation

(b)

Crystallisation

(c)

Sedimentation

(d)

None of these

Which one is a physical change?

1

(a)

Melting of ice

(b)

Melting of wax

(c)

Formation of steam from water

(d)

All of these

Making sugar solution is a _________ change.

1

(a)

physical

A physical change is generally _________

1

(a)

reversible

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

1

(a)

physical

Oxygen and _____________are must for rusting

1

(a)

water (Moisture)

A reversible change is a__________ change

1

(a)

physical

Anaerobic bacteria digest animal wastes and produce biogas.

1

(a) False

(b) True

Ships suffer a lot of damage though they are painted.

1

(a) False

(b) True

Stretching of rubber band is not a physical change.

1

(a) True

(b) False

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

1

(a) False

(b) True

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

1

(a) True

(b) False

Does it get back its Original colour?

1

(a)

Yes, it is restored to original Colour.

Does the mixture turn blue litmus red?

1

(a)

No

What kind of change is rusting?

1

(a)

Chemical change.

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

1

(a)

Chemical change

What is galvanisation?

1

(a)

The process of depositing a layer of zinc or iron is called galvanisation.

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

2

(a)

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

2

(a)

Give four characteristics of a physical change

2

(a)

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

3

(a)

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.

3

(a)

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

3

(a)

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?

5

(a)

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.

5

(a)