Fountain

Punch two holes in the lid of a jam jar and push a plastic straw a distance of two Inches through one. Fix three more straws together with adhesive tape and push through the other hole. Seal the joints with warm plasticine. Screw the lid to the jar, which should contain some water, turn it upside down and let the short straw dip into a bottle full of water: a fountain of water rises into the upper jar until the bottle is empty.
The water pours out through the long tube, and the air pressure in the jar becomes less. The air outside tries to get in and pushes the water from the bottle.