Heat, Light, and Sound Energy

Energy makes things happen. Heat, light, and sound are three forms of energy we experience every day. Each type travels differently and has its own properties.

Heat Energy

Heat energy comes from the movement of tiny particles inside an object. The faster the particles move, the hotter the object. Heat travels by conduction (through solids), convection (through liquids and gases), and radiation (through empty space).

• A camp fire gives off heat that you feel on your skin.
• A hot stove burner transfers heat to a pot by conduction.
• The Sun warms the Earth by radiating heat through space.
• Steam rising from soup is convection — warm air carrying heat upward.

Light Energy

Light energy travels as electromagnetic waves at about 300,000 km per second — faster than anything else. Light can travel through empty space. When it hits an object it can be reflected, absorbed, or transmitted.

• Sunlight is the most important natural source of light on Earth.
• A flashlight beam travels in a straight line from the bulb.
• A light bulb converts electrical energy into light energy.
• Lightning produces a flash of visible light during a storm.

Sound Energy

Sound energy travels as vibrations through matter — solids, liquids, and gases. Sound cannot travel through a vacuum. Sounds have pitch (high or low) and volume (loud or quiet).

• A drum beat creates vibrations that travel through the air to your ears.
• Your voice produces sound when your vocal cords vibrate.
• Thunder is the sound of rapidly heated air expanding during lightning.
• Music from a speaker comes from vibrating parts inside the speaker.