Question

One winter evening, after drinking a soda, you tighten the cap back on its empty 20 ounce plastic bottle and leave it in your car. Returning to your car the next morning, you find that the bottle has collapsed, looking like it was crushed overnight. In terms of heat and thermodynamics, explain what has happened to this bottle.

Answer 1

According to ideal gas law, the pressure of the gas is proportional to its temperature.

When you the empty and closed soda bottle in your car overnight in the winter, the temperature of the gas molecules inside the bottle decreases because of the heat that goes out of the bottle to the surroundings.

When the gas molecules inside the bottle cool down, its kinetic energy decreases and hence the pressure exerted by the gas on the walls decrease. Since the pressure in the bottle is less than the pressure outside, the bottle collapses because of the pressure gradient.