What is critical temperature?

Explanation

### Step-by-Step Solution

1. **Definition of Critical Temperature**:
- Critical temperature is defined as the temperature above which a gas cannot be liquefied, regardless of the pressure applied.

2. **Behavior of Gases**:
- When a gas is cooled below its critical temperature, it can be converted into a liquid by increasing the pressure. This is because the kinetic energy of the gas molecules decreases, allowing intermolecular forces to pull them closer together, resulting in a liquid state.

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