Air is a gas and as such has the property of expanding, increasing its temperature, that is to say, increasing its volume and on the contrary, when this gas decreases its temperature, it tends to contract and with it to decrease its volume.
Materials: a plastic bottle, a balloon, water and two containers. Procedure: On the one hand, water is boiled in a container and on the other hand, cold water is placed in the second container and ice cubes are added. Afterwards, the big balloon is placed in the bottle's peak, taking care that the balloon does not break or that the air escapes from the bottle. Then, the bottle is introduced into the boiling water and we watch how the balloon inflates. Then we introduce the bottle but this time in the cold water and observe that the balloon completely deflates.