Take two ice cubes in a pan, keep it still and observe it. After some time, you will observe that ice has melted to form water. Put the pan on the stove to provide heat or bring the pan in sunlight. You will observe that water has vanished. These observations depict the effect of heat on the state of matter.

Evaporation
On providing the heat to solid-state, it changes into a liquid, and on further heating, the liquid state converts into a gaseous state. But why does it happen? Heat is a type of energy and thus leads to change in the state of matter. Particles of solid absorb heat, and they move far from each other and hence convert into a liquid state. On supplying more heat to the liquid, they will further separate out and lead to a decrease in the force of attraction. This will change their state into a gaseous state. Thus, the change of state of matter is due to the heat provided to it.

Condensation
What happens during cloud formation? Small water vapors combine and form clouds, and when the clouds become heavy, they fall on earth as rain. This conversion of gas into liquid is called condensation.

Freezing
Keep a bowl filled with water inside the freezer. You will observe that after some time water converts into ice. This conversion of liquid into solid at decreasing temperature is called freezing.

Expansion
You might have seen that some gaps are left in the railway tracks during summer. Do you know the reason for that? This is due to expansion. While heating matter, particles undergo expansion since they absorb heat energy. They start moving randomly and far from each other, and the force of attraction decreases between them.

Chemical Change
Above mentioned examples were physical changes in the state of matter resulting from heating, but sometimes heating can lead to a chemical change of the matter. You might have observed a burning candle. On burning the candle, melting of wax is a physical change, while burning of wick in the presence of oxygen is a chemical change.

ICSE, Grade 6, Science

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