When we cool a gas below its condensation point, the KE of its molecules

Options

A. increases
B. decreases
C. remains the same
D. first increases then decreases

Answer

To solve the question "When we cool a gas below its condensation point, the KE of its molecules," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Kinetic Energy and Temperature Relationship**:
- Kinetic energy (KE) of gas molecules is directly related to the temperature of the gas. The equation for the average kinetic energy of gas molecules is given by:
\[ KE = \frac{3}{2} k T \]
where \( k \) is the Boltzmann constant and \( T \) is the absolute temperature.

**Hint**: Remember that kinetic energy is a function of temperature.

2. **Cooling the Gas**:
- When we cool a gas, we are effectively lowering its temperature \( T \). As the temperature decreases, the kinetic energy of the molecules also decreases because they are inversely related.

**Hint**: Think about how temperature changes affect the motion of molecules.

3. **Reaching the Condensation Point**:
- As we continue to cool the gas and it reaches its condensation point, the molecules lose enough kinetic energy that they can no longer overcome the intermolecular forces. This leads to the molecules starting to bond together.

**Hint**: Consider what happens to molecular motion when the temperature drops significantly.

4. **Behavior Below the Condensation Point**:
- Once the gas is cooled below its condensation point, the kinetic energy of the molecules continues to decrease. This decrease in kinetic energy allows the molecules to come closer together and form a liquid phase.

**Hint**: Visualize the transition from gas to liquid and how molecular interactions change.

5. **Conclusion**:
- Therefore, when we cool a gas below its condensation point, the kinetic energy of its molecules decreases.

**Final Answer**: The kinetic energy of the molecules decreases.