Question

1. You forget a toast in toaster and it turns black. Can this change be reversed?

2. You blow dry your wet hair, How can you reverse this change?

3. Why is cooking of food an irreversible change?

4 Give an example of a physical change that cannot be reversed.

5. What kind of change is observed when copper utensils appear to be greenish in
colour?

6 Which of these changes can be reversed: grain to flour, bud to flower, melting of
ghee and ripening of fruits?

7 Define the following:
a. Reversible change
b. Physical change
c. Irreversible change
d. Chemical change
G. Answer the following questions in detail.

1. Explain with the help of examples, the difference between the changes that can be
reversed and those that cannot be reversed.

2. Explain the type of changes involved in this sequence
lce cube placed in sun —— puddle of water — disappearance of puddle

3. What are physical changes? Give two examples.

4. Why is getting a new hair cut considered to be a physical change?

5 What do you observe when fireworks explode? Is anything new formed? What type
of change is it?

6. Squeezing oranges for juice is a physical change. Justify.

7 Why does the idli batter rise when kept overnight without refrigeration?

8. Places such as the mountains, where temperatures get very low during winters, the
plastic pipes meant for water transportation break. Why do you think it happens?

9. Differentiate between:
a, reversible and irreversible changes
b. physical and chemical changes
c evaporation and condensation
d. expansion and contraction

10. Look at the following pictures and write down as to whether the changes are
reversible or irreversible. For reversible changes, draw a second arrow below the
first in the opposite direction.​​

Answer 1

Answer:

no ,it is irreversible

Yes , it is reversible

Because while cooking raw food materials get cooked ,and it is irreversible because cooked food cannot be converted into raw food.