Part 1) A lightly inflated balloon is placed in a freezer. Explain the change to the size of the balloon based on the kinetic molecular theory.

Part 2. What would most likely happen to the balloon if it was instead kept outside in the sun for some time? Explain your answer based on the kinetic molecular theory.

In both cases, assume the balloon is tied tight enough so that air does not escape.

 

Part 1. A lightly inflated balloon is placed in a freezer. Explain the change to the size of the balloon based on the kinetic molecular theory.

The volume of the balloon will decrease. The kinetic molecular theory says that the particles that make up a gas are in constant, random motion and these particles collide with the walls of the container, pushing it outward until the internal pressure is equal to the outside atmospheric pressure. According to the kinetic molecular theory, temperature is the measure of average kinetic energy so if the temperature decreases, the average kinetic energy of the particles decreases so they move slower. Because of this, the particles do not collide with the inside walls of the balloon as hard so the internal pressure momentarily becomes less than the outside atmospheric pressure. As a result, the atmospheric pressure pushes on the balloon and causes its volume to decrease until these pressures are again balanced. Charles's Law explains that the volume and temperature of a gas are directly related so if the temperature decreases, the volume decreases.

Part 2. What would most likely happen to the balloon if it was instead kept outside in the sun for some time? Explain your answer based on the kinetic molecular theory.

The volume of the balloon will increase. Since the kinetic molecular theory says that temperature is the measure of average kinetic energy, if temperature increases then the average kinetic energy of the particles increases and they move faster. Because of this, the particles collide with the inside walls of the balloon more forcefully and the internal pressure is momentarily greater than the atmospheric pressure. As a result, the gas particles inside the balloon push the walls outward and cause the balloon to expand until the internal pressure decreases until this pressure is again balanced with the atmospheric pressure. Charles's Law explains that the volume and temperature of a gas are directly related so if the temperature increases, the volume increases.