All you have to do is poke holes in a plastic bottle, fill it up with water and close the cap. The tricky part is doing this with out getting yourself wet. You can either fill the bottle up with water before you poke the holes, or poke the holes in the bottle, place tape over teh holes and then fill the bottle up. Either way it will work, but be prepared for a little bit of leakage here and there.

The reason this works is a combination of pressure and surface tension of water. When water is close together, like in a bottle, the water molecules tend to stick to other water molecules. This creates a skin-like substance around the water that we call surface tension.

Also, when water comes out of a closed container something has to take its place! So by putting the holes at the bottom of the bottle we are not allowing air in the bottle. Think of it as an even exchange. However much water comes out of the bottle, the same amount of air goes inside the bottle. So while the top is closed no water leaks out but when it is open, water will start leaking!

Try this at home! See what happens when you put lots of holes in a bottle and experiment with the placment of the holes. What happens if you put the holes vertical instead of horizontal? Let us know what happens!