Recess is over and it's time to go back into the classroom and settle down.  All the students sit in nice, neat rows of desks and start to study, but you still have that little bit of energy left.  You want to go outside and run around some more.  Believe it or not, the building blocks that make up everything in our world feel the same way.  When they have a lot of energy, they want to break away, but sometimes, when they have a little less, they need to settle down.  If you still want to move around, but need to sit in a chair then you know just how a molecule feels. 

In order for a class to work, all of the students have to sit still.  In order for a solid to stay the same shape, in order for a table to hold up books, in order for a chair to hold up a person, or a wall to hold up a building, molecules have to sit still too.  They cannot go off on their own.  To be connected means to stick together.  But just because something is together does not mean it does not want to move.

We found the chairs. What happened to the students?

Once you are in class, you might still move around a little.  You might drum your fingers on the desk or tap your feet.  Even when molecules are locked together, they still move.  To vibrate means to shake back and forth, in one place.  This is the extra heat that a molecule still has from when it was flying around free as a gas.  It's kind of like the feeling you have when you were just running everywhere and you still want to run all about.  So what keeps you in class and a molecule inside of a table?

You get tired, of course!  Sometimes you ran around just enough and now sitting in class to learn feels just right.  When molecules lose heat, this makes them quiet down and want to be with others.  To attract means to pull together.  When you are tired, you might want to come together in a classroom.  When a molecule is cooled down, it wants to come together into something like a table.  Sitting in chairs is nice, since you have some space from the people around you.  You need to cool off!

These books must be very attracted to each other. They're all standing together.

Molecules feel the same way.  When they lose a lot of heat they get pulled together, but they do not touch.  Just like when you get back into class and sit down in chairs.  You are still too hot to be very close to other people, but you want to sit down and learn.  It might not last too long!  If I give you a bunch of candy, you might just start to bounce around again.  The same thing happens to molecules when they get really hot and they have enough energy to break away from the others.  To repel means to push away from something.  Just like kids, the building blocks that make up everything want to be together, but still are too hot to be right next to each other.  Molecules never lose all their energy, but they do get close enough to be locked together near each other.

Wait, are his fingers pressing down? What's wrong with this picture?

Just like you in class, a molecule can feel like it wants to be there or it can make it feel like it wants to fly away.  Even if it is tired, it still has a little bit of heat, so it still shakes a bit.  With a little more energy, it can break away and go fly around the world again.  Just like you, but not until after you are done with your classes, of course.


Science World.  "Ions, Molecules, and Compounds"  Scholastic, 2011.  <>