Vacuum Pump (Sara Wilson)
Author
Sara Wilson
Columbus Middle School - 7th/8th grade teacher
Principles
Differences between sound/light waves
Air pressure
Boiling as a function of pressure
Standards
6.4.e Students know differences in pressure, heat, air movement and humidity result in changes of weather.
7.5.g Students know how to relate the structure of the eyes and the ears to their function.
Physics 4.a Students know waves carry energy from one place to another.
Materials needed
Bell Jar and Silicone gel/Rubber pad for airtight seal
Small buzzer
Shaving cream
Balloon filled with air
Flask with water
Procedure
Sound wave investigation
Put a small buzzer underneath the bell jar and turn on
Place silicone around the base of the jar
Turn on the vacuum pump and make observations of changes to the sound level
Air Pressure investigation
Put a small amount of shaving cream or a balloon filled with air under the bell jar
Place silicone around the base of the jar
Turn on vacuum pump and make observations of changes to the shaving cream or balloon
Place a flask partially filled with water under the bell jar
Place silicone around the base of the jar
Turn on vacuum pump and make observations of changes to the water in the flask
Explanation
Sound wave investigation - Sound requires a medium (air) to travel through. When the vacuum removes all the air then the sound can no longer travel without the medium to travel through. Sound is a wave that travels by vibrating the air particles in the environment and if there is no air to vibrate no sound will occur. (Like in a vacuum)
Air Pressure Investigation - The air in an environment exerts a force (usually 1atm of pressure). If you remove the air then you remove that force and matter will expand without the force holding it in place.
Boiling as a function of Pressure Demonstration - The boiling of a liquid is a function of not only temperature but of pressure. By removing the air from a vacuum pump it causes the liquid to boil and change state to a gas.
Questions
How are sound waves different than light waves? Explain.
- Ans. - Sound waves need a medium (material like air, etc...) to travel through and light waves don't. That is why light reaches us from the sun but sound doesn't.
Why do astronauts have to use a spacesuit to live in space? Why don't they just use a mask and oxygen tank like scuba divers? Explain using academic language. - Ans. - Air exerts pressure on your body. Without that pressure your body may have problems functioning beyond not being able to breathe.
Why does water boil at a lower temperature at higher elevations? Explain with evidence. - Ans. - When there is less air pressure, like at higher elevations, then the pressure contributes to the boiling of water and allows it to boil at lower temperatures.
Everyday examples of the principles illustrated
Boiling as a function of pressure demonstration
High altitude adjustments to cooking recipes
Insulated glass limiting sound transmission
Driving to high elevations, sometimes chips bags explode from air pressure differential
Ear-popping at high elevations as well.
Photos
Image of large vacuum pump in my classroom. Missing bell jar.
Movies
Include movies that you have taken. Your movies should be placed in your youtube account.