Lesson 40: Vacuums and Suction
A vacuum is a region containing very little gas, with lower pressure than its surroundings. Suction cups, vacuum cleaners, and barometers show how pressure differences produce effects commonly described as suction.
Key Ideas
- A vacuum is a space with very little gas. A partial vacuum still contains some gas.
- Lowering air pressure in one place can let higher pressure elsewhere push air or liquid toward it. This explains many things we call suction.
- Air pressure is usually lower higher up a mountain because there is less air above us.
- Earth’s gravity helps keep the atmosphere around our planet, although some gas escapes into space.
- Differences in air pressure help create wind. Earth’s turning and features of the land also affect where the wind goes.
Vocabulary
- Vacuum: A space containing very little gas.
- Partial Vacuum: A space with less gas and lower pressure than the air around it.
- Total Vacuum: An ideal space with no gas particles. Real vacuums still contain some particles.
- Atmospheric Pressure: The push of the air around us. It acts in all directions.
- Barometer: An instrument that measures atmospheric pressure.
- Elevation: Height above sea level. As elevation increases, less air is above you, so atmospheric pressure decreases.
Discussion Questions
- In 1654, 16 horses could not pull apart two metal bowls with a vacuum inside. What force was actually holding the bowls together, and why did they fall apart the instant a valve was opened?
- Why do astronauts need pressurized suits outside the International Space Station? What would happen to the body if they did not?
- Weather maps show H for high pressure and L for low pressure. How can the pressure difference help drive wind, and why might Earth's rotation and friction keep its path from being a straight line?