20.1: Energy Resources

How can a trip to an amusement park be a learning experience?

Amusement parks use the laws of physics to generate fun! Gravity, energy, and centrifugal forces are all harnessed on various rides. Which is your favorite?

Energy

Energy is the capacity to do work. Work is the transfer of energy, so moving an object or changing the state of matter (for example, from solid to liquid) can be considered work. These activities require energy. Every living thing needs energy to live and grow.

What makes energy available whenever you need it? If you unplug a lamp, the light goes off. The lamp does not have a supply of energy to keep itself lit. The lamp uses electricity that comes through the outlet as its source of energy. The electricity comes from a power plant. The power plant has a source of energy to produce this electricity.

Fuel

The energy to make the electricity comes from fuel. Fuel stores the energy and releases it when it is needed. Fuel is any material that can release energy in a chemical change. The food you eat acts as a fuel for your body. Gasoline and diesel fuel are fuels that provide the energy for most cars, trucks, and buses. But there are many different kinds of fuel.

For fuel to be useful, its energy must be released in a way that can be controlled.

Heat

When fuel is burned, most of the energy is released as thermal energy. Heat is the transfer of thermal energy. Heat can be used to do work. Heat cooks food or warms your house. Sometimes the heat is just waste heat. It still heats the environment, though.

Thermal energy from a wood fire can boil a pot of water. If you put an egg in the pot, you can eat a hard boiled egg in 15 minutes (cool it down first!). The energy to cook the egg was stored in the wood. The wood got that energy from the Sun when it was part of a tree. The Sun generated the energy by nuclear fusion. You started the fire with a match. The head of the match stores energy as chemical energy. That energy lights the wood on fire. The fire burns as long as there is energy in the wood. Once the wood has burned up, there is no energy left in it. The fire goes out.

Using Energy

Your body gets its energy from food, but that is only a small part of the energy you use every day. Cooking your food takes energy, and so does keeping it cold in the refrigerator or the freezer. The same is true for heating or cooling your home. Whether you are turning on a light in the kitchen or riding in a car to school, you are using energy. Billions of people all around the world use energy, so there is a huge demand for resources to provide all of this energy. Not everyone uses energy equally, however. People in industrialized countries, especially the U.S., use a lot more energy than people in developing countries. Why do we need so much energy? The main reason is that almost everything that happens on Earth involves energy.

This lantern festival uses hundreds of candles for light.

The Sources of Earth's Energy

Almost all energy comes from the Sun. Plants make food energy from sunlight. Fossil fuels are made of the remains of plants and animals that stored the Sun's energy millions of years ago.

The Sun heats some areas more than others, which causes wind. The Sun's energy also drives the water cycle, which moves water over the surface of Earth. Both wind and water power can be used as renewable resources.

Earth's internal heat does not depend on the Sun for energy. This heat comes from remnant heat when the planet formed. It also comes from the decay of radioactive elements. Radioactivity is an important source of energy.

Summary

• Energy is the ability to do work or change matter.
• Energy from the Sun drives atmospheric processes on Earth, which leads to wind.
• Ancient energy from the Sun is stored in fossil fuels.

Review

1. What is energy?
2. What does it mean to say that energy changes matter from one state to another?
3. What are fuel and heat?
4. Where does the lamp in the room you're in now get its energy?

Explore More

Use this resource to answer the questions that follow.

1. What is energy? Where is energy? Where is energy in the universe?
2. Define energy. What do you apply?
3. Where do you get your energy? What type of energy is that?
4. What type of energy does a log have? What happens if you add heat to the log?
5. What is nuclear energy? What would happen if you could release the nuclear energy in a log?
6. What is the same thing as energy?
7. What does dark energy do?
8. Where does energy go? How is it created? What happens to energy? What is the universe in terms of energy?