Can you blow up a balloon without blowing?

(according to subject by Pavel Cerný, Martin Lopatár a Aleš Sirný z KMD Klobouky u Brna)

Materials:

• plastic bottle with screw cap, small hose, pipe, balloon, drill, rope, paste (putty or plasticine)

Preparation and application:

• ask for help an adult and drill into the screw cap two openings for pipe and small hose
• put them into this openings and fasten them with a paste
• put a balloon on the pipe and bind it
• let water through the hose in the bottle (see a picture). Why does balloon start to blow up?

Explanation:

Water, that you fill the bottle drive out air into the balloon and it blows up.