Can matter change its state?

 

Let's take an example of water.
We all know from our observation that water can exist in three states of matter.
1) Solid, as ice
2) liquid, as water
3) gas, as water vapour.

Q1.What happens inside the matter during the change of state?

Q.2 What happened to the particle of matter during the change of States?

Q.3 How does this change of state take place?

 
We need to answer these questions.
Let us answer these questions.

A1. When there is change of state, the particles of matter, either gain or lose the energy,

A2. When particles of matter gain energy, they separate away from each other and when particles of matter, lose energy, they come closer to each other.

A3. The change of state can occur by two methods, either by changing the pressure or by changing the temperature.
 

Effect of change of temperature:

A) When a solid is heated, it is changed into liquid or gas. And when a liquid is heated it changes into gas.
That means when you increase the temperature particles of matter, get energy and they separate away from each other.
On increasing temperature, particles absorb energy.

B) And when a gas is cooled down, it is changed into liquid and when a liquid is cooled it changes into a solid. On decreasing the temperature, particles losses energy and they come closer to each other.

Melting point: The temperature at which a solid melts to become a liquid at the atmospheric pressure is called its melting point.

Boiling point: The temperature at which a liquid starts boiling at the atmospheric pressure is known as its boiling point. Boiling is a bulk phenomenon.


Q. When is solid melts? It's temperature remains same. So where does the heat energy go?
Ans. The energy is used in increasing the kinetic energy of the particles so that they get away from each other and that is why the temperature of solid does not increase.
This is called latent heat of fusion.

Latent heat of fusion: The amount of heat energy required to change 1 kg of a solid into liquid at its melting point is called the latent heat of fusion of the solid.

When the liquid is converted into gaseous State, its temperature too doesn't increase because of latent heat of vaporization.

Latent heat of vaporization: The amount of heat energy required to change 1 kg of a liquid to vapour at atmospheric pressure, at its boiling point is called the latent heat of vaporization of the liquid.

Effect of change of pressure on the matter: 
Pressure has no effect on solid and very little effect on liquid. Its effect is mostly seen in the case of gases.

On applying pressure, the particles of matter can be brought close together and the state of matter can be changed.
For example, CO2 gas can be solidified by applying pressure and lowering temperature.