Choose the correct statement . When the temperature of a gas is increased

Options

A. its molecular kinetic energy increases
B. Molecular kinetic energy and potential energy decreases, total energy remaining constant
C. molecular potential energy increases and molecular kinetic energy decreases, total energy remaining constant
D. its molecular-potential energy increases

Answer

To solve the question regarding the behavior of a gas when its temperature is increased, we will analyze the relationship between temperature, kinetic energy, and potential energy of gas molecules.

### Step-by-Step Solution:

1. **Understanding Kinetic Energy and Temperature**:
- The average translational kinetic energy (KE) of a gas molecule is given by the formula:
\[ KE = \frac{3}{2} k T \]
where \( k \) is the Boltzmann constant and \( T \) is the temperature in Kelvin.
- This equation shows that the kinetic energy of gas molecules is directly proportional to the temperature of the gas.

**Hint**: Remember that kinetic energy increases with temperature.

2. **Effect of Increasing Temperature**:
- When the temperature of the gas increases, the average kinetic energy of the gas molecules also increases. This means that the molecules move faster and have more energy.

**Hint**: Think about how temperature relates to molecular motion.

3. **Intermolecular Forces and Potential Energy**:
- In the kinetic theory of gases, one of the assumptions is that intermolecular forces are negligible. Therefore, the potential energy (PE) associated with these forces is considered to be zero.
- Since the potential energy is zero and does not change with temperature, we conclude that the potential energy remains constant regardless of the temperature change.

**Hint**: Consider the assumptions of the kinetic theory regarding intermolecular forces.

4. **Total Energy of the Gas**:
- The total energy (E) of the gas can be expressed as:
\[ E = KE + PE \]
- Since the potential energy is zero, the total energy is equal to the kinetic energy:
\[ E = KE \]
- As the temperature increases, the kinetic energy increases, leading to an increase in the total energy of the gas.

**Hint**: Total energy is influenced by kinetic energy since potential energy is negligible.

5. **Evaluating the Statements**:
- **Statement 1**: Average molecular kinetic energy increases. (This is correct)
- **Statement 2**: Potential energy decreases. (This is incorrect; potential energy does not change)
- **Statement 3**: Potential energy increases. (This is also incorrect; potential energy remains zero)
- **Statement 4**: Potential energy remains constant. (This is correct but not listed as an option)

**Hint**: Compare each statement against your findings about kinetic and potential energy.

### Conclusion:
The correct statement when the temperature of a gas is increased is that the average molecular kinetic energy increases.

**Final Answer**: Option 1 is correct.