As a substance is changing from a liquid to a gas, the distance
between its molecules
A. increases, and the temperature of the system remains the same.
B. increases, and the temperature of the system decreases.
C. decreases, and the temperature of the system remains the same.
D. decreases, and the temperature of the system decreases.

As a substance is changing from a liquid to a gas, the distance between its molecules increases, and the temperature of the system remains the same.

Option A

Explanation:

The external energy required to change from one state to another is mostly considered as temperature. So on increase in temperature, the solid changes to liquid and the liquid changes to gases. But the temperature remains constant in the system after changing the phase.

This is because when the temperature is increased on a liquid system, the rise in temperature is utilized for breaking the bonds and thus the molecules will be distanced from each other. If we consider liquid - gas phase transition, the gas molecules are farther distanced compared to liquid molecules.

So the rise in temperature is utilized for breaking the bonds and also to provide the kinetic energy to the gas molecules as they are tend to move more freely compared to liquid. Thus, the distance between the molecules increases, and the temperature of the system remains the same on changing from liquid to gas.

temp rises, and expansion