Learning Intentions
- To learn what pressure is
- To learn how pressure affects the boiling point of a substance
Media
Pressure is the amount of force on an object divided by the area the force is exerted on.
P = F / A
The larger the force exerted, the larger the pressure.
The small the area the force is exerted on, the larger the pressure.
How much would it hurt to:
- Have a Lego brick placed on your foot?
- Step on a Lego brick?
- Be poked with a baseball bat?
- Be poked with a pen?
- Be poked with a knife?
TODO: Add pressure video
Altitude and Pressure
As the altitude increases, the amount of air pushing down from above decreases, and so the pressure on an object decreases.
Boiling Water On Mount Everest! | Earth Lab (3:28)
When there is less pressure (i.e. at high elevations, in a plane, in a vacuum chamber), substances will transition from solid to liquid (melt) and from liquid to gas (evaporate or boil) at lower temperatures. If you go very high, up into outer space 400 km above the surface of the Earth, water will boil at far below 0 degrees Celsius.
Blood Boiling Death in Space – Dara Ó Briain’s Science Club (2:39)
Would Your Blood Actually Boil In Space? (0:58)
A similar demonstration can be done with a vacuum chamber and a marshmallow.
Planet: Animal – Blobfish True Appearance! (0:11)
Demonstration – Vacuum Chamber
- I will now place a balloon in a vacuum chamber and remove the air from the chamber. What do you think will happen to the balloon?
- I will now release the vacuum, allowing air to return to the vacuum chamber. What do you think will happen to the balloon?
- I will now place a marshmallow in a vacuum chamber and remove the air from the chamber. What do you think will happen to the marshmallow?
- I will now release the vacuum, allowing air to return to the vacuum chamber. What do you think will happen to the marshmallow?