Final answer:
When an air-filled balloon is squeezed, the air molecules inside move closer together due to increased pressure from reduced volume.
Step-by-step explanation:
When an air-filled balloon is squeezed on all sides, the air molecules move closer together. This happens because squeezing the balloon decreases its volume, which increases the pressure inside the balloon. According to Boyle's Law, for a given mass of gas at constant temperature, the volume of the gas is inversely proportional to the pressure.
Thus, when you squeeze the balloon and decrease its volume, the pressure inside increases, pushing the air molecules closer together. This is similar to what happens in hot air balloons when they rise. The hot air inside is less dense than the surrounding cool air, resulting in a buoyant force that allows the balloon to rise.