Thermodynamics In Action

I take a normal empty gallon jug out of the refrigerator after it has been in there for several hours. Thus sufficiently lowering the temperature of the air inside the jug. After I take the jug out, the room temperature starts to slowly warm the jug, causing the air in the jug to expand and in turn creating pressure inside the jug. If you place the lid back onto the jug in just the right way, you can see the effect of this law of heat exchange.