Which of the following properties of liquid increases on increasing temperature :

Options

A. Vapour pressure
B. Viscosity
C. Surface tension
D. Boiling point

Answer

To determine which property of a liquid increases with temperature, we will analyze each of the given properties: vapor pressure, viscosity, surface tension, and boiling point.

### Step-by-Step Solution:

1. **Understanding Vapor Pressure**:
- Vapor pressure is the pressure exerted by the vapor in equilibrium with its liquid at a given temperature.
- As the temperature increases, the kinetic energy of the liquid molecules also increases. This leads to more molecules escaping from the liquid phase to the vapor phase.
- **Conclusion**: Vapor pressure increases with an increase in temperature.

2. **Analyzing Viscosity**:
- Viscosity is a measure of a liquid's resistance to flow. It depends on the intermolecular forces within the liquid.
- Generally, as temperature increases, the kinetic energy of the molecules increases, which reduces the intermolecular forces and allows the liquid to flow more easily.
- **Conclusion**: Viscosity typically decreases with an increase in temperature, not increases.

3. **Examining Surface Tension**:
- Surface tension is the energy required to increase the surface area of a liquid due to the cohesive forces between liquid molecules.
- As temperature increases, the kinetic energy of the molecules increases, which reduces the cohesive forces and leads to a decrease in surface tension.
- **Conclusion**: Surface tension decreases with an increase in temperature.

4. **Considering Boiling Point**:
- The boiling point of a liquid is the temperature at which its vapor pressure equals the atmospheric pressure.
- While the boiling point is related to temperature, it does not increase with temperature; rather, it is a specific temperature point for a given atmospheric pressure.
- **Conclusion**: Boiling point does not increase with an increase in temperature.

### Final Answer:
Based on the analysis, the property of liquid that increases with temperature is **vapor pressure**.