Internal energy change of a system is the heat absorbed or evolved at constant `"…............."` whereas enthalpy change is that at constant `"…..............."`.

Explanation

To solve the question regarding the conditions under which internal energy change and enthalpy change occur, we can break it down step by step.

### Step-by-Step Solution:

1. **Understanding Internal Energy Change**:
- The internal energy change of a system, denoted as ΔU, is related to the heat absorbed or evolved by the system.
- The formula for internal energy change can be expressed as:
\[
...