You can give someone a present.  You just hand it to them.  You can give someone a cold.  You might sneeze or touch food with your germy hands.  You can even give someone a headache by screaming too much.  But how do you give someone heat?  What happens when you give someone a bear hug or throw a blanket around them?  What happens when you touch the stove and yell YOUCH!  We can see gifts.  We can find germs with a microscope.  We can hear screams moving through the air.  How does heat move from one thing to another?  I hope you are scratching your head over this one, because scientists did for thousands of years.


Scientists can be a lot like you as you go through school.  A long time ago, it was like they were in scientific preschool.  They did not know many things about how the world works.  When they could not understand something, they would make up an answer, just like a little kid might tell you that rain is elf tears (it's not).  People used to believe that things had stuff called caloric inside them that made things hot, and things got hotter by getting caloric from something else.  Scientists used to believe that this was actual matter that moved between things, like a gift or a germ.  This was proved wrong when a man named Count Rumford saw that you do not need fire to boil water.  Instead, he could use something rubbing up against something else to make heat.  Like when you rub your hands together very fast.  The energy from the movement of your hands changes into heat when they rub.  This was the time that a lot of scientists moved on from preschool.


Heat is just a kind of movement, same as what spins the Earth or turns a wheel or lets you run.  It is not something we can pick up and hand to someone.  It's what lets all of the little building blocks of our world move from one place to another.  Energy is the ability to cause change.  When things heat up, these blocks really start to move, and they can change other blocks by making them move too.  They get so excited they start to dance.  When something cools down, it loses energy to the air around it.  It's like when you dance until you are tired and all your dancing made the room really warm.

Hello Mr Sunshine!


Fire crawls across the dry forest.  Bacon sizzles in a pan.  People sweat on the beach.  We see heat move all the time.  Heat flow is the idea that heat can and will move from one object to another, but only from hot to cold.  Wait wait wait.  That has to be wrong.  You have touched an icicle or a cold soda can in the past and felt the cold enter your fingers.  This is really the heat leaving your fingers and going into the cold soda.  You are feeling the missing heat!  What does the cold soda can feel?


If one person starts dancing at a party and doesn't look too silly, another person might start dancing.  Then another.  And another.  Soon the whole party will be dancing.  Now think of the building blocks of our world.  If one of them starts shaking with the energy of heat, it can start shaking the blocks around them.  Then things really start to heat up.  Transfer is when something moves from one thing to another.  Heat is energy moving from one thing to another.  If you put your hand near a toaster and feel the heat, that's just the toaster making the air around it dance!


The sun might give you a little heat.  A cold soda can might steal a little back.  But heat is not a thing.  On a small scale, it's just the building blocks in your fingers starting a dance party when the sun is out.  That is until the cold can comes along and stops the party.  Cold is a party pooper.  Maybe a hot toaster will come along and start the party up again, just as you can get a whole party dancing with your dance moves.  That is, if your dance moves are hot enough.


References

The Physics Classroom.  "Heat and Temperature."  The Physics Classroom, 2012.  <http://www.physicsclassroom.com/Class/thermalP/u18l1d.cfm>

Beyond Penguins and Polar Bears. "Cool Facts About Heat."  Ohio State University, 2009.  <http://beyondpenguins.ehe.osu.edu/issue/keeping-warm/cool-facts-about-heat>