Have you ever been amazed by a magic trick? Have you watched someone make something disappear, then make it come back again, and you had no idea how the magician did it? Now, have you ever figured out how a magic trick works and thought, "That's so easy!" Understanding how a magic trick works is just knowing the science behind it. So here's a wand. You get to do the magic trick today.
Someone find me a rabbit!
There is a large tank in front of you. Inside the tank is something that looks like a bunny made of glass. You tell your audience that you are going to make this bunny disappear, come back as gas, and then turn into a glass bunny again. How are you going to do it? Well, do not tell anyone else, but the bunny is actually made of ice. Water can come in many different forms depending on how hot or cold it is. A phase
is one stage of matter, like solid, gas or liquid, and it can change. Matter will change phases with more or less energy. With your left hand, you can turn the heat inside the tank up or down with a small twist. The wand is there to keep everyone's eyes away from what your other hand is doing.
Throw a cover over the tank. Now, turn up the heat in the tank with your left hand while you point at the audience with your wand and you ask them some questions. All things will melt if they get hot enough. The melting point
is the temperature where the building blocks in a solid begin to move around and turn into a liquid. You just turned the temperature in the tank up to 32 degrees Fahrenheit. This is where ice starts to melt. Turn it up a little higher. You want it to melt fast. All of the bonds that held the ice bunny together start to break down in the heat. Beneath the cover, the bunny starts to droop and then goes away, pouring into a drain in the tank that goes under the table. This is taking a while. Time for a joke. You ask the audience, "Where is the bunny going? It's flying away by hareplane." (Hare is another word for bunny. Get it? Now it's funny.)
You tap the tank three times with your wand for show and then throw off the cover! The bunny is gone! Everyone claps. But what's a magic show without a little smoke . . . I mean steam! Now you turn the heat up even higher, to 212 degrees Fahrenheit. The boiling point
is the temperature where a liquid turns into a gas. Now the molecules in the water below the tank start to get really excited. So excited that they start bouncing off of each other and flying up into the air. The tank starts to cloud up with all the little water molecules. It's almost like they are dancing. "What music do rabbits most like to dance to?" you ask the audience. "Hip-Hop!"
Throw that cover over the tank one last time. Remember when the water poured down the drain earlier? I did not tell you that it was pouring into a bunny-shaped mold. Now make it really cold in the tank again: 32 degrees Fahrenheit. The freezing point
is the temperature where all of the molecules start to settle down and turn into a solid. Since the building blocks do not have as much energy, they start to settle down. Not only does the steam gather back into water, but it starts to turn into ice inside our bunny mold. This might take a minute. Time for one more joke. Tell everyone that the bunny is on its way back! "What do you call a group of rabbits hopping backwards? A receding hare line."
Not so sure I want to go inside that hat again!
Fun Fact: In this trick we used water, but we could do this with anything. It would just have to get A LOT hotter and A LOT colder. It's easier to get water to change from one phase to another than most of the other things around us.
You throw off the cloth and ta-da, the bunny is back! Screaming applause, tossed flowers, bravos . . . so maybe the trick was not that great. But still. Water has three different phases: a melting point, a boiling point, and a freezing point. By changing the energy going into something, you can choose what it will look like. And you can do this magic trick over and over and over again! There's only one thing to watch out for. What do you call a rabbit who is angry over getting burnt? A hot cross bunny . . . References:
Ducksters. "Melting and Boiling" Ducksters, 2010. <http://www.ducksters.com/science/melting_and_boiling.php