Section 3: Controlling thermal energy offers many advantages.

Key Ideas   Unit Checklist

  Unit C: Section 3 – Introduction

Figure C.S.3.1 – Friction on car brakes produces enough heat to make the brakes glow red.
Figure C.S.3.2 – Car radiators cool hot engines

Hot Wheels

Moving cars generate a lot of heat. Too much heat in a car can cause car parts to break. This is why controlling heat in cars is important.

For example, car engines become very hot from burning gasoline. Overheating will wreck the engine quickly. Coolant liquid (mostly water) in various a closed system of tubes within the engine absorbs heat from the engine. Hot coolant cools in the radiator, releasing heat to the atmosphere.

Another way that cars generate heat is through friction. Friction occurs when moving parts rub against each other. For example, friction is produced when the tires on a car rub against the road. Friction is necessary to give the vehicle traction so the driver can control it. 
Figure C.S.3.3 – Tire skid marks are caused by friction.

When a driver brakes suddenly, lots of friction is produced between the tires and the road. The heat resulting from friction sometimes leaves skid marks.  If the driver accelerates quickly, the result might be smoking tires—and rubber on the road! Skid marks are the hot, disintegrating tire rubber left behind on the road.

Friction also produces heat between the brake pads and the brake disks. Sometimes, on race cars, you can see the brakes glowing bright red because they are so hot from braking on the corners!

 Watch More

Spacecraft Heat Shields

Watch this video to learn more about why spacecraft need heat shields. Space scientists are developing some new types of heat shields, such as fabric that can resist up to 3000°C.

Words to Think About:

Check out the word cloud below. It pictures the important words that you are going to learn in this section. Watch for these words, and combinations of these words, as you read. When you see them highlighted, you can click on them to learn more about what the word means.

Lessons in This Section

Lesson C8: Thermal Energy: Natural Sources
Key Question – Where is thermal energy produced naturally?

Lesson C9: Solar Energy: A Good Choice?
Key Question – What role can solar energy have in our need for energy?

Lesson C10: Thermal Energy: Technology
Key Question – How can we use technology to get the most from thermal energy?

Lesson C11: Controlling the Flow of Thermal Energy
Key Question – How can we keep heat where we want want it and prevent it from escaping?

Reading and Materials for This Section

Science in Action 7
Reading Pages: 222–237

Materials Lists for Unit:

  Try It!

Friction and Heat

Try this simple experiment to determine which types of objects generate the most heat by friction.


Materials:

  • cloth
  • metal spoon
  • wooden popsicle stick
  • plastic pen
  • strip of cardboard
Instructions:

    1. Touch the metal spoon and feel its temperature.

    2. Wrap the cloth around the metal spoon. Rub the cloth quickly 50 times up and down the metal spoon.

    3. Remove the cloth and touch the metal spoon again. Does the spoon’s temperature feel different?

    4. Repeat Steps 1 to 3 for the wooden popsicle stick, the plastic pen, and the strip of cardboard.

Questions:

Think about the following questions very carefully. Then, type or write your answers. After you have your answers, click the questions for feedback.

The metal spoon and plastic pen did not change in temperature very much. They are very smooth objects, which produced less friction and heat.
The cardboard and wooden stick warmed up most. These objects have rougher surfaces, which produced more friction and heat.