## Introduction: Water Bottle Pressure Prank! (pranked by Science)

Have a drink thief on your hands? They may be able to sneak around you, but there's no way for them to sneak around SCIENCE! With the quick water bottle pressure prank, you can thwart thieves or fascinate them with physics. Often both will happen simultaneously.

• What: Water Bottle Pressure Prank
• Does it really work: Well, are you really soaked?
• Concepts: air pressure, hydrogen bonding, cohesion
• Materials:
• 1 water bottle
• 1 pin
• 1 sucker

Truly this is one of my favorite simple demonstrations of air pressure in action. Grab a water bottle, and let's get down to pranking! It's so easy, and science will do most of the work. :)

## Step 1: Poke Tiny Holes

Grab a water bottle (the taller the better), and grab a thumbtack, pushpin, or sewing pin to poke some holes in it. With the cap still screwed on, poke several holes fairly close to the bottom. If the holes are small enough, no water should flow out except when you squeeze the bottle. If water is flowing out, you may need a smaller pin or to not poke as deeply.

## Step 2: Test Uncapping and Re-Capping

Test for bottle for prankability and get a preview of the aquatic carnage that lays ahead. Uncap your bottle to see the water flow out of your bottle, and re-cap it to make the water stop. You can even make pretty neat art this way, too if you color the water or use other liquids.

How does this work? Well, head to the next step, silly!

## Step 3: Air Pressure: the True Prankster

At all times, the air is giving you a tight hug with the force of around 14.7 pounds per square inch (at sea level). Eep! Luckily, at the same time, our body is pushing out with the same amount of force so we don't get crushed. As you're walking around, that amount of force is being directly applied all around you by the big column of air above your head.

When our bottle is capped, that force is applied to the plastic of the bottle, which pushes back with an equal force. Because the holes in the bottle are tiny, the water stays in partly because of hydrogen bonding and Van der Waal forces which makes it stick together. This is also why water drops stay together.

When the bottle is uncapped, this 14.7 pounds of pressure gets applied directly to the surface of water, which overcomes the cohesive forces of the water and makes it fly out the holes. You can also add this amount of pressure by squeezing the bottle.

Pressure on to liquids is also what lets us drink through straws. Pressure pushed down on the liquid, and we lessen the pressure inside our straw with our lungs, causing the water to fly up into it. You can give air pressure a pat on its collective back for that.

Air: the world's number one prankster!

## Step 4: Place for Pranking!

After you're all done science-ing, dry off the bottle with a towel and place in the fridge or on a table so your prank recipient is likely to grab it. Throw their name on it, offer it as a gift, any way that you think will get them hooked. Choose pranking recipients wisely. For this one, it's nice to get somebody that can appreciate science as they're getting soaked.

Should you be in a classroom setting, asking how this happens is a great and complicated question for an entire unit on air pressure. And, after all, pranking is probably humanity's best method of education. :)

Keep pranking and keep exploring! Let us know how many enemies you make!