Reversible and Irreversible Changes

Q. Dissolution of salt in water is a reversible change.

1. True
2. False

Q. Why is the burning of a candle considered to be an irreversible change, even though we get back the wax after cooling it?

Q.

A log of wood is burnt to be used in a campfire. Can the burnt wood go back to the original state of clean wood? Why or why not? What kind of change is it? [2 MARKS]

Q.

What kind of change does this image represent?

1. Reversible change.

2. Irreversible change

3. Both reversible and irreversible change.

4. No change.

Q.

2. State whether this change can be reversed or not.

(c) Rolling a ball of dough to make roti.

Q.

Growing of moustache over a boy's face is reversible change.

1. True
2. False

Q. Assertion :Burning of coal is a physical change. Reason: When coal is burnt, the chief component, carbon is changed to carbon dioxide. This process cannot be reversed.

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
3. Assertion is correct but Reason is incorrect
4. Assertion is incorrect but Reason is correct

Q.

tar is burned to build roads. Can this change be reversible?

Q. Why is burning of paper an irreversible change?

Q. Observe the given Venn diagram carefully and fill in the blanks by choosing an appropriate option.

1. $1$ - Expansion of mercury in thermometer, $2$ - Breaking of glass, $3$ - Lighting LPG stove, $4$ - Boiling an egg
2. $1$ - Falling of trees, $2$ - Occurrence of rainbow, $3$ - Growth of plants, $4$ - Tearing paper into pieces
3. $1$ - Knitting sweater from wool, $2$ - Setting of milk to form curd, $3$ - Making rice puddings, $4$ - Dissolving sugar in water
4. $1$ - Filling a water bottle, $2$ - Melting of ice, $3$ - Burning of paper, $4$ - Boiling of water

Q.

Question 2

You accidentally dropped your favourite toy and broke it. This is a change you did not want. Can this change be reversed?

Q.

Which of the following is an irreversible change?

1. Making structures of sand on a beach.

2. Making paper planes

3. Melting of ice cream

4. Punctured tyre