Why Are Light and Heat Not Matter?

In science class, you might have learned that everything is made of matter. However, you can see and feel things that aren't made up of matter. For example, light and heat are not matter. Here's an explanation of why this is and how you can tell matter and energy apart.

Why Light and Heat Aren't Matter

The universe consists of both matter and energy. The Conservation Laws state that the total amount of matter plus energy are constant in a reaction, but matter and energy may change forms. Matter includes anything that has mass. Energy describes the ability to do work. While matter may contain energy, the two are different from one another.

One easy way to tell matter and energy apart is to ask yourself whether what you observe has mass. If it doesn't, it's energy! Examples of energy include any part of the electromagnetic spectrum, which includes visible light, infrared, ultraviolet, X-ray, microwaves, radio, and gamma rays. Other forms of energy are heat (which may be considered infrared radiation), sound, potential energy, and kinetic energy.

Another way to distinguish between matter and energy is to ask whether something takes up space. Matter takes up space. You can put it in a container. While gases, liquids, and solids take up space, light and heat do not.

Usually, matter and energy are found together, so it can be tricky to distinguish between them. For example, a flame consists of matter in the form of ionized gases and particulates and energy in the form of light and heat. You can observe light and heat, but you can't weigh them on any scale.

Summary of Matter Characteristics

• Matter takes up space and has mass.
• Matter may contain energy.
• Matter may be converted to energy.

Examples of Matter and Energy

Here are examples of matter and energy that you can use to help distinguish between them:

Energy

• Sunlight
• Sound
• gamma radiation
• Energy contained in chemical bonds
• Electricity

Matter

• Hydrogen gas
• A rock
• An alpha particle (even though it can be released from radioactive decay)

Matter + Energy

Nearly any object has energy as well as matter. For example:

• A ball sitting on a shelf is made of matter, yet has potential energy. Unless the temperature is absolute zero, the ball also has thermal energy. If it's made of radioactive material, it may also emit energy in the form of radiation.
• A raindrop falling from the sky is made of matter (water), plus it has potential, kinetic, and thermal energy.
• A lit light bulb is made of matter, plus it emits energy in the form of heat and light.
• The wind consists of matter (gases in air, dust, pollen), plus it has kinetic and thermal energy.
• A sugar cube consists of matter. It contains chemical energy, thermal energy, and potential energy (depending on your frame of reference).

Other examples of things which are not matter include thoughts, dreams, and emotions. In a sense, emotions may be considered to have a basis in matter because they are related to neurochemistry. Thoughts and dreams, on the other hand, may be recorded as energy patterns.