The temperature at which the vapour pressure of liquid becomes equal to atmospheric pressure is called

Options

A. critical temperature
B. melting point
C. freezing point
D. boiling point

Explanation

To solve the question, "The temperature at which the vapour pressure of liquid becomes equal to atmospheric pressure is called," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Vapor Pressure**:
- Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid or solid phase at a given temperature. It indicates how readily a substance will evaporate.

**Hint**: Remember that vapor pressure varies with temperature; it increases as the temperature rises.

2. **Defining Atmospheric Pressure**:
- Atmospheric pressure is the pressure exerted by the weight of the atmosphere above a given point. It is approximately 101.3 kPa at sea level.

**Hint**: Atmospheric pressure can change with altitude; it decreases as you go higher.

3. **Identifying the Temperature Condition**:
- The question asks for the specific temperature at which the vapor pressure of a liquid equals the atmospheric pressure. This is a critical point for phase changes.

**Hint**: Think about the phase transition of liquids to gases.

4. **Recognizing the Boiling Point**:
- The temperature at which a liquid's vapor pressure equals the atmospheric pressure is known as the boiling point. At this point, the liquid can turn into vapor throughout the liquid, not just at the surface.

**Hint**: The boiling point can vary based on the atmospheric pressure; for example, water boils at lower temperatures at higher altitudes.

5. **Conclusion**:
- Based on the definitions and understanding of the terms, the correct answer to the question is that the temperature at which the vapor pressure of a liquid becomes equal to atmospheric pressure is called the **boiling point**.

**Final Answer**: Boiling Point