How does the (a) average kinetic energy (b) average potential energy of molecules of a substance change during its change in phase at a constant temperature, on heating ?

Explanation

To answer the question about how the average kinetic energy and average potential energy of molecules of a substance change during its phase change at a constant temperature while heating, we can break it down into two parts:

### Step-by-Step Solution

#### (a) Average Kinetic Energy
1. **Understanding Temperature and Kinetic Energy**: Temperature is a measure of the average kinetic energy of the molecules in a substance. When a substance is heated, the temperature typically increases, which would normally increase the average kinetic energy of the molecules.

2. **Phase Change at Constant Temperature**: However, during a phase change (for example, melting or boiling), the temperature remains constant despite the addition of heat. This means that the average kinetic energy of the molecules does not change during this phase transition.
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