Short Answer

Interconversion of states of matter is the process in which matter changes from one state to another—solid, liquid, or gas—by heating or cooling. When heat is added, particles gain energy and move faster, causing solids to turn into liquids and liquids into gases. When heat is removed, particles lose energy, and gases turn into liquids and liquids turn into solids.

This process shows that matter is not fixed in one form. It can change its state depending on temperature. For example, ice melts into water, and water boils to become steam. Similarly, steam cools to form water, and water freezes to become ice again.

Detailed Explanation :

Interconversion of States of Matter

Interconversion of states of matter refers to the reversible changes in the physical state of a substance. Matter exists in three main states—solid, liquid, and gas—and can shift from one state to another under certain conditions. These changes happen mainly because of heating or cooling, which affects the energy and movement of particles. Although the physical state changes during interconversion, the chemical composition of the substance remains the same.

Interconversion helps us understand how matter behaves in nature. It explains everyday phenomena such as melting of ice, boiling of water, drying of clothes, formation of dew, and freezing of water. These changes do not create a new substance; instead, they only alter the form of the same substance.

How Interconversion Happens

Role of Heat Energy

Heat is the main factor that causes interconversion. When heat is added to a substance, its particles gain energy and move faster. This increased movement weakens the attraction between particles and leads to a change in state.

When heat is removed, particles lose energy and move slowly. This strengthens the force of attraction, causing particles to come closer and change the state of matter.

From Solid to Liquid – Melting

Melting is the process in which a solid changes into a liquid on heating. When a solid is heated:

Its particles gain energy.
They vibrate faster.
The strong attraction between particles becomes weaker.
Particles break free from their fixed positions.

Example: Ice melts to form water at 0°C.

From Liquid to Gas – Evaporation and Boiling

A liquid can change into gas in two ways: evaporation and boiling.

Evaporation happens slowly at any temperature. It occurs only on the surface of the liquid.
Example: Wet clothes dry because water slowly evaporates.

Boiling happens quickly at a fixed temperature known as the boiling point. It occurs throughout the liquid.
Example: Water boils at 100°C to form steam.

From Gas to Liquid – Condensation

Condensation is the process in which a gas becomes a liquid when cooled. When gas loses heat:

Its particles lose energy.
They move more slowly.
They come closer and form liquid.

Example: Steam cools to form water droplets on a cold surface.

Another example is the formation of dew on leaves early in the morning.

From Liquid to Solid – Freezing

Freezing is the process in which a liquid becomes a solid on cooling. When a liquid cools:

Its particles lose energy.
They move slowly.
The force of attraction increases.
Particles settle in fixed positions.

Example: Water freezes to become ice at 0°C.

From Solid to Gas – Sublimation

Some solids change directly from solid to gas without becoming liquid. This process is called sublimation.

Example:

Camphor, dry ice (solid carbon dioxide), and naphthalene balls sublimate.
Dry ice turns directly into carbon dioxide gas.

From Gas to Solid – Deposition

Deposition is the process in which a gas changes directly into a solid without becoming liquid.

Example:

Frost formation on leaves in winter.
Ice crystals forming on cold surfaces.

Why Interconversion Is Reversible

The states of matter change only because of heat gain or heat loss. If the temperature is reversed, matter goes back to its original state. This is why the process is reversible.

Examples:

Ice → Water → Ice
Water → Steam → Water
Dry ice → Carbon dioxide gas → Dry ice

The chemical identity of the substance remains the same in all states.

Conclusion

Interconversion of states of matter is the reversible change of matter from one state to another due to heating or cooling. Melting, freezing, evaporation, boiling, condensation, sublimation, and deposition are all part of this process. Interconversion happens because particles gain or lose energy, which changes their movement and arrangement. This concept helps us understand many natural and everyday processes involving matter.