Phase Change in a Liquid due to Increase in Temperature:

When the temperature of a liquid increases, it can undergo a phase change from a liquid state to a gas state. This phase change is known as vaporization or boiling. The molecules in a liquid gain energy with an increase in temperature, and as a result, they move faster and have a higher kinetic energy. This increased kinetic energy allows the molecules to overcome the intermolecular forces holding them together and escape into the gas phase.

Explanation:

When a liquid is heated, the temperature of the liquid increases. As the temperature rises, the average kinetic energy of the molecules also increases. The molecules in the liquid move more rapidly and collide with each other more frequently. These collisions cause the molecules to break free from the attractive forces holding them together in the liquid phase.

As the liquid continues to be heated, the molecules gain enough energy to overcome the intermolecular forces completely. At this point, the liquid starts to boil, and the phase change from liquid to gas occurs. The process of vaporization or boiling involves the conversion of liquid molecules into gas molecules.

Key Points:
- An increase in temperature provides the necessary energy for the liquid molecules to overcome intermolecular forces.
- The increased kinetic energy of the molecules allows them to move more rapidly and collide more frequently.
- These collisions lead to the breaking of intermolecular forces and the escape of molecules into the gas phase.
- The liquid undergoes a phase change from a liquid state to a gas state.
- This phase change is known as vaporization or boiling.
- Therefore, an increase in temperature in a liquid causes a phase change to a gas (option A).