At constant volume, for a fixed number of moles of a gas the pressure of the gas increases with rise of temperature due to

Pressure exerted on the walls of the container by gas molecules is equal to the change in momentum per unit time and area. At constant volume, for a fixed number of moles of a gas, with increase in temperature, the pressure of the gas increases due to increase in their average molecular speed. This increase leads to change in momentum during collisions.