What Is Matter?

Introduction

Look around you. The chair you sit on, the water in your bottle, the air you breathe and even your own body are all made of the same basic "stuff" — matter. Chemistry is the science of matter: what it is made of, what properties it has and how it changes. Before we can study any of those questions, we need a clear, testable definition of what counts as matter and what does not. This page gives that definition and shows how to apply it.

Core explanation

The definition. Matter is anything that has mass and takes up space . Both conditions must be met. Mass tells us how much matter there is; volume tells us how much space it occupies.

Matter in three familiar states. Matter on Earth is usually found as a solid (such as ice, wood or iron), a liquid (such as water, milk or cooking oil) or a gas (such as air, steam or the carbon dioxide in a fizzy drink). The state can change — ice melts to water and water boils to steam — but the matter itself is still there. A fourth state, plasma , exists in lightning, neon signs and the Sun, where gases are so hot that electrons are torn from atoms.

Invisible matter is still matter. We cannot see air, but we can show it has both properties. A balloon full of air has a slightly greater mass than the same balloon empty, so air has mass. An upside-down glass pushed into water traps air, and the water cannot rise to fill it, so air takes up space. The same reasoning applies to water vapour, which is invisible even though the steam cloud above a kettle (tiny liquid droplets) is visible.

Living and non-living matter. Plants, animals and people are matter too. A growing tree gains mass by building new material mainly from carbon dioxide in the air and water from the soil. Living things follow exactly the same chemical rules as non-living materials.

Substances. Chemists call a particular kind of matter with fixed properties a substance — for example pure water, iron or table salt. Most everyday materials, such as sea water, air or wood, are mixtures of several substances. You will study mixtures in a later unit.

Why a precise definition matters. Science relies on definitions that can be tested. "Has mass and takes up space" can be checked with a balance and a measuring cylinder. A vague definition such as "things you can touch" fails: you cannot easily touch air, but it is matter.

Step-by-step reasoning

To decide whether something is matter, ask two questions in order:

1. Does it have mass? Could it, at least in principle, be weighed on a balance (perhaps inside a sealed container)? 2. Does it take up space? Does it fill a volume that nothing else can occupy at the same time? 3. If the answer to both is yes, it is matter. 4. If either answer is no — as for light, sound, heat or a thought — it is not matter, even if it is real and important.

Visual explanation

Imagine three sealed jars on a balance: one holding a stone (solid), one holding water (liquid) and one pumped full of air (gas). Each jar reads more than an identical empty, evacuated jar. In the particle simulation, the solid shows particles packed in a fixed pattern, the liquid shows particles close together but sliding past each other, and the gas shows particles far apart and moving quickly in all directions. All three contain particles — all three are matter.

Real-world analogy

Think of a crowded school hall. Every student has a body (mass) and needs somewhere to stand (space). Two students cannot stand on exactly the same spot at the same time. Matter behaves the same way: every bit of it has mass and claims its own space, even the "invisible" students — the air particles — packed between everyone else.

Real-world example

Car tyres are filled with air. Because air is matter, it takes up space and pushes outwards on the rubber, which lets the tyre carry the weight of the car. If air were not matter, pumping it in would change nothing. Engineers calculate how much air (by mass) a tyre needs at a particular pressure for safe driving.

Why?

Why is sunlight not matter even though it can warm you? Light is a form of energy. It carries energy from place to place but it does not take up space in the way matter does — two beams of light can pass straight through each other — and a jar does not get measurably heavier when light shines into it. Matter and energy are closely linked, but they are not the same thing.

Common misconception

Many students think gases are "nothing" or weigh nothing because they are invisible and seem to float. In fact 1 litre of air at room conditions has a mass of about 1.2 g. A classroom full of air has a mass of roughly 200 kg — heavier than two adults.

Worked example

Question: Is the steam cloud above a boiling kettle matter? Is the heat from the kettle matter?

Reasoning: The visible cloud consists of tiny droplets of liquid water, and the invisible steam next to the spout is water vapour; both have mass and take up space. Heat is energy transferred from a hot object to a cooler one; it has no mass of its own and occupies no space.

Answer: The steam and the cloud are matter; the heat is not.

Quick check

1. State the two conditions something must satisfy to be classed as matter. Answer: It must have mass and it must take up space (have volume).

Exam focus

Learn the definition word for word: "Matter is anything that has mass and occupies space." Examiners often ask you to sort a list (for example air, light, water, sound, sand) into matter and not-matter, and to justify one choice using the definition. Always mention both mass and space in your justification.

Advanced insight

Einstein's equation E = mc² shows that energy and mass are related: a hot object has a very slightly greater mass than the same object when cold. The difference is far too small to detect with any laboratory balance, so for all of chemistry at this level we treat matter and energy as separate things.

Summary

Matter is anything that has mass and takes up space. It exists as solids, liquids and gases (and plasma), including invisible gases such as air and water vapour. Living things are matter too. Light, heat, sound and ideas are not matter, even though they are real. A precise, testable definition lets us decide what chemistry studies.

Practice questions

1. Sort into matter and not matter: sand, sound, oxygen, light, orange juice. Answer: Matter: sand, oxygen, orange juice. Not matter: sound, light. 2. Describe a simple test showing that air takes up space. Answer: Push an upside-down empty glass straight down into water; the water does not fill the glass because air trapped inside occupies the space. 3. A balloon has a mass of 3.0 g empty and 4.1 g when blown up. What does this show? Answer: The air inside has a mass of about 1.1 g, so air has mass and is matter. 4. Give one reason why "things you can touch" is a poor definition of matter. Answer: Gases such as air are matter but cannot easily be touched or seen, so the definition would wrongly exclude them.