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Air Pressure- Magic Bottle (Katie Flanagan)

Author

Katie Flanagan

Principle(s) Illustrated

  1. Air Pressure

Standards

  • 6.6.e - Students know differences in pressure, heat, air movement, and humidity result in changes in weather.
  • There are many other concepts in science that relate to this concept of air pressure, however, I could not find any other standards that directly addressed it.

Questioning Script

Prior knowledge & experience:

Students need to know about atmospheric pressure.

Root question:

What will happen to the water when a hole is drilled in the bottom of a bottle, the bottle is filled up with water, but the cap is left on the bottle?  Now what will happen if the cap is removed from the bottle?

Target response:

When the cap is on the bottle the water will not drip out of the bottle, however, when the cap is removed the water will drain out. The reason the water will not drain out when the cap is on is because the pressure outside the bottle is the same as the pressure inside, so the water will stay where it is.  However, when you remove the cap, air will enter the bottle making the pressure inside greater than the pressure outside so the water will want to go to the area with lower pressure. 

Common Misconceptions:

The common misconception is that if there is a hole in the bottle, regardless if the cap is on or not, the water will drip out of the hole.

Materials & Procedures:

Materials:

  • Plastic Bottle with cap (any size will work)
  • Water
  • Food Coloring 
  • Nail
Procedures:
  • Poke the nail through the plastic bottle on the side in the bottom 1/4 of the bottle
  • Make sure you have a good size hole that water could easily flow through
  • Drop a couple of drops of food coloring in the bottle so students can easily see the water flow
  • While covering the hole with your finger, fill the bottle with water
  • Screw the cap on the bottle
  • Show the students that no water is flowing out the hole
  • Now unscrew the cap (make sure you are holding the bottle over a sink or a bin) and the water should flow out.
  • Take the cap on and off a few times to show the effect.

Other Variations:

Another variation that shows a similar concept is to take a larger 2 L bottle and poke three holes in the side. This will show that the bottom hole has the most pressure and therefore the water will pour out the furthest, while the top hole has less pressure and will only pour out a short distance.

Photographs and Movies


References

The Motivational Power of Discrepant Events

The Science Wondershop
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