Final answer:
The behavior of a gas within a container is such that when the temperature rises, the gas molecules move faster, leading to more frequent and forceful collisions with the container walls, thus increasing the pressure.
Step-by-step explanation:
The phenomenon being described is related to the behavior of gases, and it can be explained using the ideal gas law and kinetic theory. As the temperature of a gas in a rigid container increases, the kinetic energy of the gas molecules also increases. This higher kinetic energy means the molecules move faster and collide with the container walls more often and with greater force. According to the ideal gas law (PV=nRT), if the volume (V) is constant, and the amount (n) of gas inside the container does not change, an increase in temperature (T) will result in an increase of pressure (P). Consequently, when it gets warmer, the pressure exerted by the gas on its container increases.