When an ideal gas undergoes unrestrained expansion, no cooling occurs because the molecules

Options

A. Are above the inversion temperature
B. Exert no attractive forces on each other
C. Do work equal to loss in kinetic energy
D. Collide without losing energy

Explanation

### Step-by-Step Solution

1. **Understanding Unrestrained Expansion**:
- Unrestrained expansion, also known as free expansion, occurs when a gas expands into a vacuum without doing any work on the surroundings. In this process, the gas molecules spread out to fill the available volume.

2. **Identifying the Cooling Effect**:
- In many real gases, when they undergo free expansion, they can experience a cooling effect due to the Joule-Thomson effect. This effect describes how the temperature of a gas changes when it expands at constant enthalpy.

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