A gas in a sealed container is kept at a constant volume. The temperature of the gas is increased. What happens to the pressure of the gas?
Let’s say that this is our gas in a container of fixed volume. If we heat the gas, that will increase its temperature. And that means that the average kinetic energy, the average speed of the particles in the gas, will increase. Therefore, when a particle of gas runs into the wall of the container, it will now exert a greater force on that wall because of its greater speed. If we add up the effect of all the collisions of these faster-moving particles with the walls of the container, that is equal to what we call the pressure of the gas.
We’ve seen that through heating the temperature of our gas is increased. This increases the average speed of particles in the gas, which means that they collide with the walls of the container at that much greater speed, which will have the overall effect of increasing the gas pressure.
The phenomenon we’re describing goes by the name of Gay-Lussac’s law. This law says that when a gas is at a constant volume, the gas pressure is proportional to the gas temperature. And this tells us how to answer our question. When the temperature of a gas held at constant volume increases, the gas pressure also increases.