Heat and Liquid Nitrogen

CloudsGarbage can in the air

Throw a polystyrene coffee cup full of liquid nitrogen high into the air. Don't throw the cup! A cloud will temporarily be formed. This shows that if you cool the air enough, the water vapor in it condenses.  

Balloons in Liquid Nitrogen

Pour liquid nitrogen over an air filled balloon, it will collapse in a vivid demonstration of the relationship between temperature and volume for a fixed mass of gas at a constant pressure. If immersed in a container of liquid nitrogen, the air in the balloon liquefies. Try it with helium instead of air, that way the balloon ascends when it warms, a nice discrepant event.

Carnations in Liquid Nitrogen

Flowers are frozen in liquid nitrogen and then smashed, showing that temperature has a dramatic effect on the properties of materials, especially if they contain water.

Liquid Nitrogen Cannon

The world's best pop-gun can be made from a piece of steel pipe, closed at one end, and a small metal 'test tube' fastened to a short length of wire, used as a dipper. Fill the dipper with liquid nitrogen after having cooled it in the nitrogen. Carefully lower this dipper with liquid nitrogen into the pipe and cork off the pipe. When the pipe is shaken the liquid spills from the dipper and rapidly becomes a gas when it contacts the pipe. The gas produced when the liquid nitrogen vaporizes, at atmospheric pressure occupies about one thousand times the volume of the liquid. Confinement in the tube causes high pressure and violent expulsion of the cork.

Explosion of a Soda Bottle

A 2-liter soda bottle is tightly capped off with about a pint of liquid nitrogen in it. Then it is placed on the ground with a 50 gallon plastic, not metal, garbage can inverted over it. It takes a few minutes before the bottle explodes and projects the garbage can 10 to 20 meters into the air. This demonstration of a liquid turning into a gas should never be done in a small room and should only be done in a large room, such as a gymnasium, with a plastic garbage can over the bottle to muffle the noise. Outside using a 2-liter bottle with a cup of liquid nitrogen, it's louder than both barrels of a 12-gauge shotgun going off together and the small pieces of frozen plastic will be both sharp and fast moving, so make sure no one is within 30 meters or so of it.

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