Explanation for Constant Temperature during Change of State:
The temperature remains constant during the change of state of a substance because the heat energy being supplied is utilized in overcoming the forces of attraction between the particles of the substance, rather than increasing the temperature.

Key Points:
- When a substance changes its state from solid to liquid or liquid to gas, the intermolecular forces between the particles need to be overcome.
- The heat energy supplied is used to break these intermolecular forces rather than increasing the kinetic energy of the particles.
- This results in a constant temperature as the energy is being utilized in the phase change process.
- Once all the particles have overcome the intermolecular forces, the temperature starts to increase again.

Example:
For example, when ice at 0°C is heated, the heat energy supplied is used to break the hydrogen bonds between the water molecules in the ice, converting it into water at 0°C. The temperature remains constant at 0°C until all the ice has melted, after which the temperature starts to rise.

Conclusion:
In conclusion, the temperature remains constant during the change of state of a substance because the heat energy is being utilized in overcoming intermolecular forces rather than increasing the kinetic energy of the particles. This phenomenon is known as latent heat, and it plays a crucial role in maintaining the temperature during phase changes.