### Theory:

Have you ever wondered why ice turns into puddles of water on sweltering day?

We already learn that matter occurs in three states -- solid, liquid and gas.

Know that matters can change its states, when state change occurs a substances properties also change. Similarly if the state change is reversed the substance will recover the properties which it had before.

We will do two experiment to understand this concept clear.

Experiment 1:

Take some water in a vessel and heat it in medium flame, after couple minutes observe what is happening.

Experiment 2:

Get some ice pellets and keep it in room temperature or expose those in low flame, observe what happening to those ice pellets after couple of minutes.

In above two experiments we treated the liquid and the solid (ice) with heat, and we can observe that both liquid and the solid are changed their state.

Therefore if we applied heat energy to liquid it becomes gas and if we do the same thing to the ice it becomes liquid. Therefore we can define the above process as vaporization and condensation.
Vaporization: The process of the liquid converting its physical state to gaseous state is know as vaporization.

Condensation: The process of the gas converting its physical state to liquid state is know as Condensation. This is also called as reverse vaporization
But the question is how this transformation is happening?
How matters transforms it's states:

When we apply the heat energy to the solid, the particles in the solids are absorbs the heat energy and this additional energy break the attracting force between the molecules.

This leads to the rearrangement to the substance because the attracting force no longer holding the particles as tightly. That's why the solid ice cube melts and transform to liquid when heat is applied.
This same will happen if liquid heated, the attractive forces between the molecules break, which leading them to widely dispersed and a gas to form.
Boiling point: The temperature at which a liquid begins to boil at the atmospheric pressure is known as its boiling point
Remember that the boiling point of water is $100\mathrm{°}\phantom{\rule{0.147em}{0ex}}C$.

Similarly, when the solid objects are heated, the attractive force between the molecules break, then the particles leave their fixed positions and start moving more freely.
Melting point: The temperature at which a solid substance melts to become a liquid at the atmospheric pressure is called the melting point of that substance.
The melting point of an ice is $0\mathrm{°}\phantom{\rule{0.147em}{0ex}}C$.

Therefore the matter change its state respective to the energy applied to the matter. The below figure explains how the matter are changing its state once the energy is applied.