We could get a bottle to talk to us.
We put cold water into a bottle, left it outside until the water was really cold, emptied the bottle, then brought it inside again.
We splashed a little water onto the lid of the bottle and turned the lid upside down on the bottle.
The bottle looked empty (but was in fact filled with cold air).
When we pur our warm hands around the bottle the cap jumped up and down on the top of the bottle.
Here's the explanation: When you place your hands around the bottle, you warm the air inside it.
Air expands when it warms up and tries to escape from the bottle. The wet cap at first acts as a seal and keeps the air in place, but eventually the air has expanded enough to push the top upwards. If the cap doesn’t slide or fall, and you keep your hands placed around the bottle, you can continue to make it jump. The bottle looks like it is chatting to us.