How to Make a Pen Cap Submarine – Easy and Simple – Simple Science Experiment

All you need is a pen top, blue tack or plasticine, a paper clip, an empty plastic drink bottle, and some water. There is a little bit of trapped air inside the pen cap. When the air pressure increases in the bottle (i.e. when you press on the bottle’s sides) more water is forced up into the pen cap and the pen cap will sink. Release the pressure and the pen cap will rise.