What Is Energy? Light, Heat, and Sound!

What You'll Learn

• Light energy travels super fast — it's the fastest thing in the universe.
• Heat (thermal) energy moves from warmer things to cooler things.
• Sound energy is made by vibrations — tiny invisible back-and-forth movements.
• Sound travels slower than light, so we see lightning before we hear thunder.
• Energy can change form — the Sun gives us BOTH light and heat at the same time.

Words to Know

Energy

The ability to make things happen or cause change.

The Sun's energy makes plants grow and warms your skin.

Light energy

Energy you can see, like from the Sun, a lamp, or fire.

A flashlight turns battery energy into light energy.

Heat energy

Energy you feel as warmth, like from a fire or the Sun.

Rubbing your hands together makes heat energy.

Sound energy

Energy made by vibrations that travel through the air to your ears.

A clapping hand makes sound energy.

Vibration

A tiny, fast, back-and-forth movement.

A guitar string's vibration makes the sound you hear.

Thermal energy

Another name for heat energy inside things.

A hot cocoa has more thermal energy than a cold lemonade.

Check What You Learned

Fun Facts

• Energy is the ability to do work — to make things happen or cause change.

  Source: U.S. Energy Information Administration, "Energy Explained for Kids"

• Light travels at about 186,000 miles per second (299,792,458 meters per second) in a vacuum — the fastest speed in the universe.

  Source: NASA, "How Fast Does Light Travel?"

• Sound travels slower than light — that is why you see lightning before you hear thunder.

  Source: NOAA National Severe Storms Laboratory, "Lightning Safety"

• Sound is caused by vibrations — back-and-forth movements that travel through air (or water, or solids) to our ears.

  Source: NASA, "What Is Sound?"

• Heat (thermal) energy always flows from a warmer object to a cooler one until they are the same temperature.

  Source: American Chemical Society, "Energy Foundations for High School Chemistry" — 2nd Law of Thermodynamics, heat flow

• The Sun gives off both light energy and heat energy at the same time — energy can change from one form to another.

  Source: NASA, "The Sun's Energy"