Do Not Open Bottle - Soda Prank It's the ultimate prank... email to friend
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It's the ultimate prank using the simplest of props... a plastic soda bottle filled with water. Even though the words, "DO NOT OPEN" are printed on the bottle, people just can't resist the temptation. Watch out, the fun is just beginning.

Materials

Two plastic soda bottles (1-liter size works well)
Cap
Large nail
Sharpie pen
Thumb tack

Hey, if you're a kid who is trying to do this experiment, get an adult to help you poke the holes in the bottle. You don't want to hurt YOUR hand!

Experiment
Video

The Leak-Proof Bottle

Use the nail to poke a hole on the side of the bottle close to the bottom.
Cover the hole with your finger while you fill the bottle with water all the way to the top. Screw on the cap.
Slowly take your finger away from the hole. Are you ready for the water to come rushing out. Hey, there's no leak?
Unscrew the cap and watch what happens. Okay, now it's time to stand back!

The "Do Not Open" Bottle Trick

Start with a new plastic soda bottle (don't use the one from the previous experiment). Use the permanent marker to write DO NOT OPEN! in fat letters on the bottom half of the bottle.
Use a sharp push pin (thumb tack) and carefully poke tiny holes through the bottle at the bottom of the letters (the letters will help hide the holes).
Place the bottle in a deep sink or pan and fill it with water. The tricky part is that the water will leak out of the holes as you're filling the bottle. Keep the water running as you screw on the cap. Don't squeeze the bottle or it will start leaking before you're ready.
Set the bottle on the kitchen counter (word-side out) where someone can see it as they pass by. Stay close enough to watch what happens. Eventually, someone is bound to ask about the bottle. Play dumb with, œI dunno when they ask about it. Let them unscrew the cap and you'll witness science in action!

How does it work?

Think about why the bottle spews water when the cap is loosened. It's kind of a tag team combo between gravity and air pressure. Gravity is pushing downward on the water whether the lid's on the bottle or not. Air pressure can't do anything until it somehow gets into the bottle. When the lid is on, air pressure can't get into the bottle to push on the surface of the water. It does, however, push against the outside of the bottle on all sides. Since the outside atmospheric pressure is greater than the force of gravity, most of the water stays in the bottle. When the lid is uncapped, though, the outside atmospheric pressure (14.7 pounds per square inch at sea level) and the force of gravity push down on the water at the same time. The water shoots out and the nosy person gets a scientific (but well-deserved) soaking.