As a substance changes from liquid to gas, the average distance between molecules (1) decreases (2)increases

(3) remains the same

is it (2) ?

Certainly.

As a substance changes from liquid to gas, the average distance between molecules (1) increases.

As a substance changes from liquid to gas, the average distance between molecules increases.

To understand why this happens, let's discuss the properties of liquids and gases. In a liquid state, molecules are close to each other and have stronger intermolecular forces that hold them together, allowing them to move past one another. This results in a fixed volume and shape of the liquid.

When heat is added to a liquid, the kinetic energy (or energy of motion) of the molecules increases. As a result, some molecules gain enough energy to overcome the intermolecular forces holding them in the liquid state. These molecules escape from the liquid and become a gas.

In the gaseous state, molecules are much farther apart from each other compared to the liquid state. They have high kinetic energy and move rapidly in random directions. The intermolecular forces in gases are very weak, so the molecules are free to move independently.

Therefore, as a substance changes from a liquid to a gas, the average distance between molecules increases because the molecules spread out in the gaseous state. So, the correct answer is (2) increases.