January 18, 2014

Hey guys,

Today we’re going to look at what happens when you lower the pressure inside a sealed container.  We’ll be using the vacuum chamber to do a couple of cool demos.  We’ll then show you how to make a mini version of a vacuum chamber yourself!

Episode 4: The Vacuum Chamber

 

Remember from the last episode (barefoot on a bed of nails) that Pressure = Force/Area.

Pressure differences create unbalances forces and those forces make things move.  (don’t forget about the marshmallow going through the soda can!)  There was a pressure difference between the inside and the outside of the balloon and that’s why the balloon expanded outward.  There was a pressure difference between the air in the shaving cream and the surrounding air so the shaving cream also expanded.  Pressure differences can sometimes create huge forces.  This You Tube video shows how pressure differences can crush a barrel…Check it out:

Isn’t that cool!!!

In this case, water was boiled in the barrel which pushed most of the air out of the barrel.  The lid was then screwed on and the water vapor was quickly cooled in ice water.  As it cooled, the water vapor turned back into liquid water and took up way less space and so the pressure became very low inside the barrel.  The pressure outside the barrel (normal air pressure) was bigger and so it pushed in on the barrel and crushed it.

The Challenge:

Remember the challenge was to make your own balloon bottle and get the balloon to inflate without blowing into it.  You’ll need a bottle that has stiff sides to get it too work.  Don’t forget to drill a small hole in the side at the bottom for air to escape.  You can also use the balloon bottle as a water pump; I’ll leave that to you to explore for yourself.  Good luck and email me a video of your finished product in action!

chris@stokedaboutscience.com