Why Are Light and Heat Not Matter?

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.

What Is the Definition of "Matter" in Physics?

Matter has many definitions, but the most common is that it is any substance which has mass and occupies space. All physical objects are composed of matter, in the form of atoms, which are in turn composed of protons, neutrons, and electrons.

The idea that matter consisted of building blocks or particles originated with the Greek philosophers Democritus (470-380 BC) and Leucippus (490 BC).

Examples of Matter (and What Isn't Matter)

Matter is built from atoms. The most basic atom, the isotope of hydrogen known as protium, is a single proton. So, although subatomic particles aren't always considered forms of matter by some scientists, you could consider Protium to be the exception. Some people consider electrons and neutrons to also be forms of matter. Otherwise, any substance built of atoms consists of matter. Examples include:

• Atoms (hydrogen, helium, californium, uranium)
• Molecules (water, ozone, nitrogen gas, sucrose)
• Ions (Ca2+, SO42-)
• Polymers and Macromolecules (cellulose, chitin, proteins, DNA)
• Mixtures (oil and water, salt and sand, air)
• Complex Forms (a chair, a planet, a ball)

While protons, neutrons, and electrons are the building blocks of atoms, these particles are themselves based on fermions. Quarks and leptons typically aren't considered forms of matter, although they do fit certain definitions of the term. At most levels, it's simplest to state simply that matter consists of atoms.

Antimatter is still matter, although the particles annihilate ordinary matter when they contact each other. Antimatter exists naturally on Earth, although in extremely small quantities.

Then, there are things that either have no mass or at least have no rest mass. Things that are not matter include:

• Light
• Sound
• Heat
• Thoughts
• Dreams
• Emotions

Photons have no mass, so they are an example of something in physics that is notcomprised of matter. They are also not considered "objects" in the traditional sense, as they cannot exist in a stationary state.

Phases of Matter

Matter can exist in various phases: solid, liquid, gas, or plasma. Most substances can transition between these phases based on the amount of heat the material absorbs (or loses). There are additional states or phases of matter, including Bose-Einstein condensates, fermionic condensates, and quark-gluon plasma.

Matter Versus Mass

Note that while matter has mass, and massive objects contain matter, the two terms are not exactly synonymous, at least in physics. Matter is not conserved, while mass is conserved in closed systems. According to the theory of special relativity, matter in a closed system may disappear. Mass, on the other hand, may never have been created nor destroyed, although it can be converted into energy. The sum of mass and energy remains constant in a closed system.

In physics, one way to distinguish between mass and matter is to define matter as a substance consisting of particles that exhibit rest mass. Even so, in physics and chemistry, matter exhibits wave-particle duality, so it has properties of both waves and particles.