Question

What would happen if you put a balloon in the refrigerator ?

Answer 1

As the air cools it compresses and therefore exerts less pressure on the balloon. If cold enough your balloon will be visibly deflated. If you then bring back to room temperature it will return to normal. And if you heat it, it will get bigger as the air expands.

You can see this in lots of examples. Put an empty plastic bottle with a tight lid in freezer, same thing. Plastic gas cans in a hit garage expand and look like they will burst.