Question

Conceptual Questions :-

1. What kind of a change is represented by the freezing of lakes and ponds in cold countries? Explain.

2. Is it essential for two substances to interact for undergoing a change? Explain giving an example.

3. A magnet attracts a piece of iron. What kind of change is this ? Will it be different if you break the magnet into two pieces ?

4. Are chemical changes undesirable changes? Explain all.

5. Are all physical changes reversible? Explain with example.

6. Are changes of states (solid → liquid → gas) reversible incase of all substances? Is it a physical or chemical change?​

Answer 1

${\large{\rm{\underline{\orange{Questions :-}}}}}$

1. What kind of a change is represented by the freezing of lakes and ponds in cold countries? Explain.

2. Is it essential for two substances to interact for undergoing a change? Explain giving an example.

3. A magnet attracts a piece of iron. What kind of change is this ? Will it be different if you break the magnet into two pieces ?

4. Are chemical changes undesirable changes? Explain all.

5. Are all physical changes reversible? Explain with example.

6. Are changes of states (solid → liquid → gas) reversible incase of all substances? Is it a physical or chemical change?

${\large{\rm{\underline{\color{violet}{Answers :-}}}}}$

1. Freezing of lakes and ponds in cold countries does not undergo any change in its composition. Hence is a physical change.

2. Yes. For two substances to undergo a change, the two substances need to undergo an interaction.

3. Attraction of a piece of iron by magnet is a physical change. As the magnetization of a magnet is a temporary, reversible change and without any change in molecular composition. On breaking of a magnet into two pieces each pieces acts as an individual magnet. Hence, no change will take place.

4. No. Chemical changes are desirable. For example digestion of food, respiration, etc, are desirable.

5. No. All physical changes are not reversible. If a glass is broken into pieces. It cannot be formed into the original glass again.

6. No changes of state are reversible in only few cases. But, they are physical changes as there is no change in composition of the substances.