Irreversible change

Q.

A melted chocolate is kept in a refrigerator. It solidifies again. This is an irreversible change.

1. True
2. False

Q.

Select the chemical changes from the following:
(i) Digestion of food
(ii) Boiling of water
(iii) Cooking of food
(iv) Tarnishing of silver spoon
(v) Sublimation of iodine
(vi) Electrolysis of water
(vii) Melting of butter in a pan
(viii) Burning of wood

Q.

Which of the following change cannot be reversed?

1. Hardening of cement

2. Freezing of ice cream

3. Opening a door

4. Melting of chocolate

Q.

A few activities of Sooraj on a particular morning are mentioned below.
1. To walk through a waterlogged, Sooraj reduced the length of his pants by folding it.
2. In school, he ate an apple during his snacks break.
Classify the above activities as reversible and irreversible.

1. Reversible change - 1
   Irreversible change - 2
2. Reversible change - none
   Irreversible change - 1, 2
3. Reversible change - 2
   Irreversible change - 1
4. Reversible change - 1, 2
   Irreversible change - none

Q. Melting of wax is a/an _________ change , while burning of a candle is a/an _________ change.

1. reversible, reversible
2. reversible, irreversible
3. irreversible, reversible
4. irreversible, irreversible

Q.

Classify the following change in as many ways as possible.
Burning of paper

Q.

Sublimation of any substance is

1. Physical change

2. chemical change

3. Both

4. All of these

Q. Which of the following are features of chemical changes?

1. Formation of a new substance
2. Physical mixing of two substances
3. Change cannot be undone physically
4. Change in chemical composition

Q.

Which of the following is not an example of change?

1. Rusting of iron

2. Burning of wood

3. Standing house

4. Ripening of fruits

Q. Which among the following is an example of irreversible change?

1. Making structures of sand on beach
2. Melting of ice
3. Cutting of trees
4. Making paper planes

Q.

Silver anklet forms a black coating when kept in air for a longer duration. This is a

1. Physical change

2. Both A and B

3. Periodic change

4. Chemical change

Q. The formation of brown coloured flaky layer (rust) on iron nail when kept in air for a long time is a _________.

1. reversible change
2. fast change
3. chemical change
4. physical change

Q.

The following figure shows an irreversible change because _____.

1. flour is changing its physical form to become baked bread
2. baked bread cannot be converted back to flour
3. baked bread on mixing with water can be converted back to flour
4. baked bread can be converted back to flour by cooling it

Q. Burning something is a/an ___________ change.

1. reversible
2. irreversible
3. periodic
4. temporary

Q.

Making stars by cutting it out from a sheet of paper is a reversible change.

1. True
2. False

Q. Which of the following is an irreversible change?

1. Melting of ice cream
2. Formation of curd
3. Folding of paper
4. Melting of ice

Q.

A hissing sound is produced when baking soda is added to vinegar. This sound is due to evolution of:

1. Hydrogen gas

2. Oxygen gas

3. Carbon dioxide gas

4. Nitrogen dioxide gas