BALLOON IN A BOTTLE
Fill the plastic bottle with hot water.
Swirl the water around to make the bottle hot and then pour it out.
Refill the bottle one-fourth full with hot water and place the balloon over the mouth of the bottle.
Fill the large bowl with ice water and place the bottle in the bowl.
Watch as all of the air is taken from the balloon. It might even get sucked into the bottle.
What happens? The hot air in the bottle expands as the cool air outside the bottle contracts. When you first place the balloon over the mouth of the bottle, the air in the bottle is hot. As the air cools from the ice water outside the bottle it contracts and pushes the balloon into the bottle. This is why the air is taken from the balloon and sometimes gets sucked into the bottle.