Explain why the pressure exerted by a gas increases as they are heated at constant volume, with references to the kinetic theory of gases.

The kinetic theory models gas particles as points moving around with a given velocity. Heating the particles causes the transfer of heat energy, which is then used to increase the particles kinetic energy. This causes them to move with a greater velocity and hence exert an increased force on the sides of the container, which in turn causes the pressure to increase (recall pressure is defined as the normal force per unit area).