Editing Liquid Nitrogen (section)

== Why This Works ==

Liquid Nitrogen is extremely cold, and sits at about -321 degrees Fahrenheit, or about -196 degrees Celsius. It is very dangerous that it is this cold, which is why we state time and again throughout this write-up to use all necessary safety precautions. The expansion rate of liquid Nitrogen is about 700:1, or for every 1 liter of liquid Nitrogen we have, we will get 700 liters of Nitrogen gas when it warms to room temperature. Please make sure the lid on the container is never tight for this reason, because it can explode if that expanding gas builds up pressure. This is also why this demonstration needs to be performed in a ventilated area.

;Molecule Dance: This is a fun way to have kids recognize how molecules interact. When the kids are moving fast, they are like gas molecules, which fill their entire container and move very quickly. When they were moving moderately, that is like liquid molecules, which spread out over an area but stay relatively close together. When they moved slowly, that was like solid molecules, which do not move very much and stay very close together. Make sure to remind them that they were able to move from these different states by either adding heat (liquid to gas) or removing heat (liquid to solid).
;Balloon: This helps to build the connection between moving molecules and temperature, which was started in the Molecule Dance. When the balloon is at room temperature, the air inside is moving quickly, and takes up a lot of space. As the balloon is cooled by the liquid Nitrogen, the air inside moves much more slowly, as it loses heat to the LN2. This makes the air inside condense, and allows the balloon to "deflate" and fit into the thermos. After pulling it out, the air inside will warm back up and expand the balloon back to its original size.
;Banana and Flowers: This shows the effects of heat loss on living organisms, such as ourselves. We know that we have water inside of our bodies, and plants are similar in that they have a lot of water. When the flower or Banana are put inside of the liquid Nitrogen, the water in their cells starts to freeze. Water is unique in that, when it goes from a liquid to solid, it expands. Most of the rest of matter contracts when it goes from a liquid to solid state! When the ice forms in those cells, it causes them to expand as well, and this can break some of the cells as it happens. The frozen water and broken cells become apparent when we pull the plant out of the liquid Nitrogen and shatter it! At the end of the performance, you can show students that the banana and flower petals rapidly wilt and brown when they thaw, due to these broken cells.
;Leidenfrost Effect: We need to remember two things to understand this effect. First, that the liquid Nitrogen is extremely cold. Second, that we are extremely hot compared to it. There is an over 400 degree difference (Fahrenheit) between our bodies and the liquid Nitrogen. So, when it first comes in contact with our hand, some of this liquid will ''instantly turn to gas''. The rest of the liquid lands on this gas layer, and rolls across it, never touching us! This effect only works, however, if we do not keep prolonged exposure to the cold liquid. Prolonged exposure allows the gas layer to escape, and that would result in frostbite or worse. Also, this does NOT work for solid-on-solid contact. The solid objects we use are solids at room temperature as well, so they would not create this gas layer, and would quickly freeze to your exposed hand. That is why you need to wear gloves when handling a cold solid.
;Bimetallic Plate: Metals are solids at room temperature, and are known for being very strong and durable. Metals cannot become "more solid" by cooling them down, but they can contract slightly. The bimetallic plate takes advantage of this fact. Certain types of metal contract at different rates, and some contract more than others. In the case of this strip, we know we have Bronze and Nickel, and we can see that by cooling it, the bronze side curls over. This tells us that the Bronze side contracts at a faster rate than the Nickel! As we let the strip warm back to room temperature, we will see that it straightens out again. This is because the opposite is also true; the Bronze side expands at a greater rate than the Nickel as well!
;Racquetball: This demonstration shows how the elasticity of a material is temperature dependent. Many of us heard as kids that you need to "warm up" a rubber band before you use it, and there is some fact to that. A materials elasticity, or how much it can stretch or bounce, is dependent on the temperature of the material. The racquetball we know is elastic at room temperature, but after we put it in the thermos it will start to cool rapidly. Remind students that the racquetball cannot freeze, since it does not have a lot of water in it. What can happen, however, is that the ball will get less and less elastic, to the point where it will not bounce or stretch at all. It is also worth noting that racquetballs are hollow, with air in the center to help with the bounce. We know that air will contract and condense when cooled, so the inside of the ball will have a small ''vacuum'', or empty space, inside of it. This empty space is what causes it to make a loud popping sound when it shatters!
''Note: The reason why the ball will not shatter when thrown against a wood surface is because, surprisingly, the wood is too elastic!''