If the pressure remains constant and the volume increases, what happens to the temperature?

• A. Temperature increases.
• B. Temperature remains the same.
• C. Temperature becomes negative.
• D. Temperature decreases.

Answer: (D)

When a gas is kept at constant pressure, temperature is directly related to volume for a fixed amount of gas. This follows the relation PV = nRT, so with P and n fixed, temperature is proportional to volume: T = PV/(nR). If you increase the volume while keeping pressure constant, the temperature must rise to maintain the equality. Remember to use Kelvin for temperature in gas-law calculations; doubling the volume at the same pressure and amount of gas doubles the temperature in Kelvin. So the correct outcome is that the temperature increases. The idea that temperature would stay the same or decrease doesn’t align with this direct V–T relationship under constant pressure.