Things need :
§ Piece of balloon
§ Lemon peel
§ Broad mouthed bottle or rubber band
v Fill the bottle with water till the brim.
v Put a peel or lemon in the shape of a boat in water.
v Stretch the piece of balloon on the mouth of the bottle and with the rubber band seal it in place on the mouth of the jar. The balloon should be slightly stretched. It should not sag.
v Using you finger gently press down on the lid (balloon cover ) and the lemon peel will dive to the bottom of the jar.
v Release you finger the lemon peel will return to the top of the jar.
The pressure exerted by hand squashes air bubbles in the lemon peel allowing the water. This makes the lemon peel heavy and sink. When the finger is released the air in the lemon peel expands and returns to the top.