[3 Mark Question Answer]

Question 13 Marks

Give two differences between a physical change and a chemical change.

Answer

Property	Physical change	Chemical change
Nature of change	The change is temporary and can be reversed by simple physical methods.	The change is permanent and cannot be reversed by simple physical methods.
Formation of new substance	No new substance are formed.	New substances with different compositions and properties are formed.

Question 23 Marks

Differentiate between the following changes with suitable examples.
Reversible and irreversible changes.

Answer

Reversible

These are changes that can be reversed (returned to its original form) by reversing the conditions.
Examples : Melting of ice, evaporation of water, glowing of an electric bulb, dissolving sugar in water, etc.

Irreversible changes :

These are changes that cannot be reversed.
Examples : Cooking of food, Rusting of iron, burning of paper, curdling of milk, etc.

Question 33 Marks

Differentiate between the following changes with suitable examples.
Desirable and undesirable changes Ans.

Answer

Desirable

These are changes that are useful to human beings.
Examples : Cooking of food, ripening of fruits, change of season, formation of curd from milk, etc.

Undesirable changes :

These are changes that are harmful to us or cause destruction.
Examples: Cyclone, spoilage of food, curdling of milk, soil erosion, rusing of iron, etc.

Question 43 Marks

Differentiate between the following changes with suitable examples.
Periodic and non-periodic changes

Answer

Periodic

These are changes that are repeated at regular intervals of time.
Examples – Change of seasons, high tides and low tides, heartbeat, swinging of a clock pendulum, etc.

Non-periodic changes :

Question 53 Marks

Differentiate between the following changes with suitable examples.
Slow and fast changes

Answer

Slow :

Changes that occur over a long period of time (few hours or many years) are called slow changes.
Examples : Rusting of iron, germination of seed, tooth decay, soil formation, freezing of water, etc.

Fast changes :

Changes that occur within a very short period of time or within seconds are called fast changes.
Examples : Burning of paper lightning, during a thunderstorm, occurrence of earthquakes, etc.

Question 63 Marks

Differentiate between the following changes with suitable examples.
Natural and man-made changes

Answer

Natural:

These are changes that occur in nature on their own.
We have no control over
Examples : Change of day and night, earthquakes, growth of living beings, volcano etc

Man-made changes :

CHEMISTRY [3 Mark Question Answer]