I'm going to throw you into the middle of Antarctica.  Why?  Science!  That's why.  What better place to learn about heat and how it moves than in one of the coldest places on Earth?  Do not worry, I will make it up to you in three paragraphs.  Before we get started, though, there's a word that I want you to learn that is not really a word.  Confused?  Of course you are.  This is a root word that can be used to build other words.  Here's the word: therm.  It means heat.  Now any time you see "therm" in a word, you'll know its meaning has something to do with heat.  Just don't use it all by itself.  You will sound strange.

Who wants to go play outside?

Your teeth are chattering.  We better get you warmed up.  To do that, we will need to move the energy out of something and into you.  Exothermic means to let out heat.  "Exo" means outside, while . . . wait, what does "therm" mean again?  Heat!  Right!  So exothermic means "to let out heat."  Lights and heaters let off heat, but they kind of cheat because they use electricity and fire.  We do not have that down here in Antarctica.  What can we use?

Luckily for us there are other ways of getting heat out of something.  There are things you can mix together that will become hot without using fire or electricity!  To liberate means to set free.  In science we can use liberate to talk about letting out energy.  When we mix this salt water with this magnesium powder, it will let off heat and get up to a very hot 98 degrees in just over a minute!  Feeling warm?  Good!  Now I am going to toss you into the middle of the desert.  Told you I would make it up to you.

You are sweating a lot.  We need to cool you down.  Get ready to put those root words to work again.  Endothermic means to take in heat.  "Endo" means inside.  "Therm" means . . . right, heat!  So endothermic means to pull heat inside.  Many reactions will let out heat and make the things around them hotter, but some will make the things around them colder!  If you thought letting out heat was a good trick, wait until you see this.  You might want to wipe the sweat out of your eyes so you can really see.

Looks like a great day for a walk!

I do not need to tell you that we do not have a refrigerator out here in the desert.  Also, all the ice has melted.  Again, there are other ways of making cold.  To absorb means to take in.  When it comes to heat energy, we can make something colder if we absorb heat.  By mixing two new things, like water and this ammonium nitrate powder, we will make something new that will pull heat in and then grow colder and colder until . . . it freezes.  Here, put this on your head.  Nice, right?

How can this refrigerator keep me cool if it's covered in magnets!

So, we warmed you up in Antarctica but did not use any fire or electricity.  We cooled you down in the desert with no refrigerators or ice.  By understanding how to make something let out heat or take it in, we can change our heat with some water and different kinds of powder.  You know the old saying: The early scientist gets the therm . . .  Just kidding.  I made that up.


WBGU.  "Exothermic and Endothermic Reaction"  Got Science, 2006.  <http://wbgu.org/wbgumultimedia/gotscience/page110117.php>