Liquid Nitrogen Cannon

States of Matter

• LN₂ cannon
• cork(s)
• Liquid Nitrogen
• Mallet to pound in cork (optional)
• Cork screw, for when you pound the cork in too hard.

Key Points:

• The cannon is very warm compared to the LN₂.
• When the LN₂ is poured into the cannon, the cannon starts to warm it up.
• When you heat a liquid it turns into a gas.
• Gases take up much more space than liquids.
• As it expands, the Nitrogen tries to take up more space, but the cork is stopping it.
• After a second or so, the Nitrogen is pushing hard enough to pop the cork out.

Warnings:

• Like any projectile weapon, don't fire the cannon directly at anyone.
• When the cork is ejected, some LN₂ also flies out the barrel. Be sure not to aim the cannon over anyone, as the LN₂ might spray onto them (yes this has actually happened)
• If the cork gets stuck, open the valve before you start messing with it and trying to free it.

Things to talk about:

• This demo should be done quickly. There are a lot of states of matter demos, and they all show pretty much the same thing, so there's no need to drag them all out.
• Restate that a gas takes up much more space than a liquid, and we can use this to do work.
• Show them the cannon and tell them how it works.
• There usually isn't much time to talk once you've started pouring the LN₂. in, so it's a good idea to get done explaining before you DO the demo.
• Make sure the valve is open. The valve we currently use is open when it's pointing directly outward.
• Pour in (a couple tablespoons of) LN₂. Quickly pound in the cork. It doesn't have to be jammed all the way into the barrel. Just try it a few times and you'll get the hang of it.
• As soon as the cork is set, close the valve.
• After launching the cork, you can ask them if they want to see that again. Open valve, pour in a little more LN₂, put in another cork, close valve.

Click here for the Adobe PDF version of this demo (text only), for printing purposes.