Final answer:
A balloon shrinks when cooled because Charles's Law states that the volume of a gas is directly proportional to its temperature at constant pressure. As the balloon cools, the gas molecules slow down, take up less space, and the balloon's volume decreases.
Step-by-step explanation:
The reason a balloon shrinks when it is put on the snow or cooled in a refrigerator is due to the principles of gas laws, specifically Charles's Law. This law states that the volume of a gas is directly proportional to its temperature when the pressure is held constant. When the balloon is placed in a cold environment, the gas molecules inside the balloon slow down and take up less space, causing the balloon to shrink in size.
In the case of the classroom demonstration, the shrunken balloon contains liquid nitrogen, which is the light blue liquid, and likely nitrogen in solid form as snow-like crystals. As the balloon warms up, the nitrogen transitions from its solid and liquid states back to a gas, causing the balloon to re-expand.
In summation, the decrease in temperature causes the gas molecules within the balloon to slow down and take up less space, which decreases the internal pressure and volume, leading to the balloon's shrinkage.