Which of the following is a physical change?

1

(a)

Rusting of iron

(b)

Combustion of magnesium ribbon

(c)

Burning of candle

(d)

Melting of wax

A chemical change may involve

1

(a)

change in colour only

(b)

change in temperature only

(c)

evolution of gas only

(d)

All of the above

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)

Galvanisation is a process used to prevent the rusting of which of the following?

1

(a)

Iron

(b)

Zinc

(c)

Aluminium

(d)

Copper

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

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

1

(a)

physical

Iron benches kept in lawns and gardens get __________ It is a _______change because a new ________ is formed.

1

(a)

rusted, chemical, substance

Energy is ________ in the formation of curd from milk.

1

(a)

evolved

The presence of _________ in seawater makes the process of rust formation on ships faster

1

(a)

salt

Souring of milk is a ___________ change

1

(a)

chemical

Cutting a log of wood into pieces is a chemical change.

1

(a) True

(b) False

Formation of manure from leaves is a physical change.

1

(a) True

(b) False

Iron pipes coated with zinc do not get rusted easily.

1

(a) False

(b) True

Iron and rust are the same substances.

1

(a) True

(b) False

Condensation of steam is not a chemical change.

1

(a) False

(b) True

Does the mixture turn red litmus blue?

1

(a)

Does the mixture turn blue litmus red?

Does the mixture turn blue litmus red?

1

(a)

No

On the basis of this test, how do you classify the aqueous Solution-acidic or basic?

1

(a)

On the basis of this test, how do you classify the aqueous Solution-acidic or basic?

Do you see any change in the colour of the solution?

1

(a)

Yes, the solution becomes green from blue

Has it changed in any way?

1

(a)

There is a brown coat deposited on the nail

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)

Complete the following reaction Ca (OH₂) + CO₂ \(\longrightarrow\)

2

(a)

What is the nature of magnesium oxide solution?

2

(a)

How would you show that setting of curd is a chemical change?

3

(a)

Explain why burning of wood and cutting it into small pieces are considered as two different types of changes.

3

(a)

Describe how crystals of copper sulphate are prepared.

3

(a)

Explain how painting of an iron gate prevents it from rusting.

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)