Question

Why does temperature remain constant during the change of state?

Answer 1

Hint: We know that matter exists in three states i.e. solid, liquid and gases. The change of state of matter is the physical changes of matter. Some common changes of state are melting, freezing, condensation etc. we are here to find the reason for temperature constant during the change of state.

Complete answer:
As we all know that there are three states of matter i.e. solid, liquid and gases. The change of state of matter is defined as the change in physical properties of matter. These changes are reversible changes which do not involve the change in chemical properties of matter.
The change of state of matter of a substance occurs when solid is converted to liquid and liquid is converted to gas. This change is brought up by imparting heat energy to it at a constant temperature. Some common changes of state are melting, freezing, condensation, sublimation, deposition and vaporization.
The process of change of a substance from solid state into liquid state by absorbing heat at a particular temperature is called melting or fusion and the temperature at which this happens is called the melting point.
The process of change of a substance from liquid state into gaseous state at a particular temperature is called boiling and the temperature at which this happens is called the boiling point.
The heat energy applied during this change of state of matter is used in breaking the intermolecular forces and other attractive forces. This is due to the latent heat as the heat supplied to increase the temperature of the substance is used up in transformation of states of matter of the substances, hence the temperature remains constant. Therefore, no external heat is absorbed or released.

Note:
The temperature of any substance remains constant as all the heat energy provided is used up in breaking intermolecular or attractive forces to change the states of matter. Also, the latent heat is the property related to enthalpy. It is the heat energy absorbed and released during phase change of a substance either solid to liquid or liquid to gas and vice versa.