From kinetic theory, the ball is filled with gas molecules that is colliding with each other and moving at different speed (kinetic energy) and temperature will increase. So, when is it froozen, the temperature of the gas decrease causing a slowing down in the speed of the gas molecules and therefore, the balloon will shrink.
The balloon will shrink because the average kinetic energy of gas molecules in a balloon decreases with fall in temperature. Butif we warm the balloon , it will rise.
