Lesson 1.1 - What is Heat?

The world around you is filled with things that you can use without knowing anything about them.  One of the important things that separates people from animals is that people can learn about how things work and manipulate them to satisfy their needs. 

Imagine it is very cold outside, and a bird is sitting in a tree and a girl sitting under that tree.  The bird has to rely on its feathers to keep warm; it has no other options for the bird.  The girl is probably warmly dressed, and if she gets cold, she can go inside her house to warm up.  The girl did not have to know anything about how the clothes keep her warm or how the furnace transfers heat to warm the house. 

To make intelligent choices, people need to understand the basic science of the things they use.  In this lesson, you will learn all about heat. 

Read the first two paragraphs in The Nature of Heat on page 82.

Was Count Rumford the first person to observe that heat was generated by friction?

Not likely! People used friction to start fires for thousands of years before Rumford.  Look back at the picture of a bow drill in use on page 81. 

What is so great about Count Rumford noticing that heat is produced when metal cuts metal?  What the story did not tell was the scientific theory of heat before the 1800s. 

The theory that scientists had about heat involved a fluid called caloric.  The theory said that heat was a fluid that could flow from one object to another.  Every object had a certain amount of this fluid in it.  For example, imagine an ice cube in your hand.  The caloric fluid in your hand would flow to the ice cube.  Because your hand has less caloric fluid in it that the ice cube does, you hand feels colder.  Because the ice cube now gains more caloric fluid, it melts.  Let's hope it sounded like a good theory at that time!

Rumford noticed that friction could produce unlimited heat.  If heat was this caloric fluid, there should only have been so much of it in objects such as the drill and the cannon.  Both the drill and the cannon became very hot when the hole was drilled. Where did the caloric fluid come from?  It was his observations that made other scientists look more closely at the nature of heat.  Eventually, the caloric theory of heat was replaced by the modern theory of heat.   


Go to the next page to learn more about heat.