You know those kids.  The ones that run screaming around the playground, bumping into everyone and everything and trying to get as far away from the school as they can.  Maybe you are one of these kids.  That's just fine.  I am here to tell you that when kids run around and scream and bump into each other with a lot of energy, they are acting a lot like excited molecules.  When kids or molecules have a lot of energy, there's no telling what they will do.

The teacher lines all of the kids up outside.  Everyone is nice and quiet, but then the bell rings.  The kids break free!  They all go different ways, away from each other and the classroom.  Molecules do the same thing when they heat up.  If water gets hot enough, the small parts break away from each other and fly up into the air.  To be independent means to be free from all other things.  When the bell rings for recess, the kids are free from the school.  When things get hot enough, molecules break free from each other.

Hey, where's everybody going?

Of course, kids who are set loose might not look where they are going.  They will run every which way and might even crash into each other, only to get right back up again and run the other way.  Hot molecules are no different.  They have so much energy, they crash into each other like bumper cars but then keep right on going just to crash into another soon after that.  To collide means to run into something else.  But you know this will not stop the crazy kids.  And it will not stop molecules either.  They have got places to go.

Oh boy, will they ever go places.  Anywhere you let them, really.  If you release a group of kids into a classroom, they will fill it.  A playground?  They will fill it.  A park?  They will run to its very ends.  If you think kids are hard to keep in one place, try gases.  They can fly, so they will fly every way possible.  If you put a gas in a balloon, molecules will fill every part of it.  If they are let loose in the sky, they will spread out as far and wide as they can.  Volume is how much space something takes up.  No matter how small or how big the space is, gas (and a group of kids) will fill the shape.  Sometimes this can mean trouble for the space.

Most playgrounds have a fence around them.  That does not stop the crazy kids.  They like to bang up against that fence or even try to climb it.  Molecules also try to get out of the space they are in.  They crash into each other and they crash into whatever walls are holding them inside.  Pressure is how much force something puts against something else when touching it.  Gas wants out of the balloon.  Kids want out of the playground. 

Watch your step. The first one is a long one.

And you thought kids could be crazy.  They may run away from the school.  They may bump into each other.  They may fill every space they go into.  And they may almost break the fences that hold them in.  But at least they cannot fly up into the air like gases.  If kids could do that, I think a lot more teachers would quit their jobs.


Chem 4 Kids.  "Looking For a Gas"  Chem 4 Kids, 2010.  <>

Science Kidz.  "Gas Facts For Kids"  Science Kidz, 2012.  <>