Air Pressure Prank – Fun with Frederick and Fleming

In our weekly summer segment Friday Fun with Frederick & Fleming, we do different little science experiments that would be fun to do with your kids. The goal with all of these is to use things you could find around the house or pick up at almost any store for a very little amount of money.

In today’s segment we did an example of the air pressure pushing down around us that can also be done as a little practical joke.

Items Needed:

  • Plastic bottle
  • Push pin
  • Water
  • Marker

Instructions:

  1. Fill the bottle with water all the way to the top and screw the top on tight.
  2. Take your marker and write something like “Do Not Open” on it to peak the interest of those who see it.
  3. On the marker lines, carefully poke a few holes with the push pin. Adult supervision with the push pin is advised.
  4. Leave the bottle around and see if anyone opens it up.  If they do, water will come out the holes.

Science:

We have air pressing down around us at all times.  We typically don’t feel it though because we are so used to it.  By putting the lid on the bottle and poking only small holes, between the air pressure and the surface tension of the water, the water won’t come out.  The air is pressing down on the outside of the bottle and that is keeping the water in it as the pressure outside is greater than the pressure inside.

BUT, if you open the lid on the bottle, the air pressure now is able to push against the water from the top and therefore push it out the holes in the bottle giving the person who opened it a little surprise shower.

By squeezing the bottle, you are increasing the pressure on the inside of the bottle so it is now a greater pressure inside than outside and the water will squirt out.

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