Boiling at Constant Pressure

Boiling is a process in which a liquid changes to a gas at a constant pressure. When a liquid boils at constant pressure, it absorbs heat from the surroundings to overcome the intermolecular forces between the molecules.

Increased Entropy

The correct answer to the question is option 'D', entropy. When a liquid boils at constant pressure, the entropy of the system increases. Entropy is a measure of the disorder or randomness of a system. When a liquid boils, the molecules gain enough energy to overcome the intermolecular forces holding them together, and they escape into the gas phase. This results in an increase in the randomness of the system, which is reflected in an increase in entropy.

Other Parameters

While temperature, heat of vaporisation, and kinetic energy all play a role in the process of boiling, they do not increase when a liquid boils at constant pressure.

- Temperature: The temperature of a liquid remains constant during the boiling process until all of the liquid has been converted to a gas. This is because the energy being added to the system is being used to overcome the intermolecular forces between the molecules, rather than to increase the temperature of the liquid.
- Heat of Vaporisation: The heat of vaporisation is the amount of energy required to convert a given amount of a liquid into a gas at a constant temperature. While the heat of vaporisation is an important parameter in the process of boiling, it does not change when a liquid boils at constant pressure.
- Kinetic Energy: The kinetic energy of the molecules in a liquid increases as the temperature of the liquid increases. However, when a liquid boils at constant pressure, the temperature remains constant, so the kinetic energy of the molecules does not increase.

Conclusion

In conclusion, when a liquid boils at constant pressure, the entropy of the system increases. This is because the boiling process results in an increase in the randomness of the system, which is reflected in an increase in entropy. While temperature, heat of vaporisation, and kinetic energy are all important parameters in the process of boiling, they do not increase when a liquid boils at constant pressure.