What Is Energy?

Core Idea

Energy is the ability to make things happen — to move objects, create heat, produce light, or cause change. Energy is everywhere: in sunlight, in food, in a stretched rubber band, and in a rolling ball. You cannot see energy itself, but you can see what it does. Without energy, nothing in the universe would ever change or move.

How It's Best Learned

Have students identify "what has energy" in photos of everyday scenes (a burning candle, a moving car, food on a plate). Wind up a toy and watch it go to see stored energy turn into motion. Discuss how their breakfast gave them energy to run at recess.

Common Misconceptions

• Energy is a substance you can hold or see. (Energy is not a material; it is a property that describes an object's ability to cause change.)
• Only moving things have energy. (A rock at the top of a hill, a stretched spring, and food all have stored energy even though they are not moving.)
• Energy gets "used up" and disappears. (Energy changes form but is never created or destroyed.)
• Only electricity is "real" energy. (Heat, light, sound, motion, and stored chemical energy are all forms of energy.)

Explainer

Energy is one of the most important ideas in all of science. You cannot hold it in your hand or put it in a jar, but energy is behind every single thing that happens in the universe. When a ball rolls, that is energy. When a light bulb glows, that is energy. When you eat breakfast and then run around at recess, energy from food is powering your muscles. Energy is the ability to cause change.

Energy comes in many forms. A moving soccer ball has energy because of its motion. A book on a high shelf has energy because of its position — if it falls, that stored energy turns into motion. The food you eat has chemical energy stored in its molecules. A battery has chemical energy too. Sunlight carries energy that plants use to grow. Even the warmth you feel from a campfire is energy in the form of heat.

One of the trickiest things about energy is that you cannot create it or destroy it. Energy only changes from one form to another. When you turn on a flashlight, chemical energy in the battery becomes electrical energy, which then becomes light and a little bit of heat. The total amount of energy stays the same — it just moves around and changes form.

Scientists study energy because understanding it helps explain how everything works, from tiny atoms vibrating to enormous stars shining. Once you start noticing energy, you will see it everywhere: in the wind blowing through trees, in the sound of music, in the warmth of the Sun on your face, and in every step you take. Energy connects all the different parts of science together.