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How to Demonstrate a High Pressure System

Air pressure is the force exerted on the earth's surface by the weight of tiny air particles. When air molecules cool, they become more dense. As molecule density increases, so does the weight. The heavy, dense air molecules plummet toward the earth's surface. When the molecules collide with the surface, they exert a force. This force is known as high air pressure. Demonstrating high air pressure isn't difficult as long as you have the right illustrations and knowledge.

Things You'll Need

Pressure system illustrations
Balloon
Small fan
Pin

Instructions

- 1
  Gently squeeze the person's arm to whom you're demonstrating high air pressure and explain that the person felt a force exerted on her arm as a result of the molecules in your hand colliding with her arm. Explain that this is roughly the same thing that happens in atmospheric pressure, just not on the same scale. In this case, the person's arm is the earth's surface and your hand is densely compacted air molecules.
- 2
  Show an illustration of a low pressure system and an illustration of a high pressure system. Explain that in a low pressure system the surface of the earth is warm, which heats the air molecules. Explain that when molecules heat up they scatter and that air molecules on their own are extremely light so they rise up away from the earth's surface, relieving pressure.
- 3
  Explain, using the illustration of the high pressure system, that high atmospheric temperature is cold and when heated rising air molecules get high enough they cool. Explain that cooling molecules clump up together, becoming densely packed balls of air molecules. Explain that these cold, dense clumps get too heavy for the hot air to keep pushing up so they fall back down to the earth and exert the force of high air pressure on its surface.
- 4
  Take a balloon and blow it up. Explain that as it fills with hot air from your lungs the surface area expands making the balloon light, just like heated air molecules. Turn on a small air fan and blast the underside of the balloon to demonstrate how the light, scattered air molecules rise. Turn down the power of the fan and do your best to keep the balloon hovering above it.
- 5
  Pop the floating balloon with a pin and explain why it falls. Explain that the balloon falls because the rubber contracts as a result of the hot air escaping. Explain that the air pressure from the fan isn't enough to keep the dense rubber afloat so it falls to the ground. Explain that when the balloon hits the ground it exerts a force as a result of the molecules in the balloon colliding with the molecules in the floor.

Nature