According to the description of the ideal gas law, what happens to volume when temperature increases at constant pressure?

• A. Volume decreases.
• B. Volume increases proportionally to the temperature.
• C. Volume remains constant.
• D. Volume increases with pressure.

Answer: (B)

At constant pressure, the volume of an ideal gas is directly proportional to temperature (in kelvin) because PV = nRT with P and n fixed gives V = nRT / P. As temperature rises, the gas particles gain kinetic energy and need more space to maintain the same pressure, so the volume increases linearly with T. For example, doubling the temperature in kelvin doubles the volume. Remember to use kelvin for temperature (T(K) = T(°C) + 273.15). The volume would not stay the same or decrease with rising temperature at constant pressure, and it isn’t determined by pressure alone in this condition.