Look around you. Everything you see is made of matter. The chair you are sitting in, a table, a houseplant, the air you breathe – all of these things are made of matter.
But, what exactly is matter?
What is Matter?
Matter is anything that is made of atoms. Atoms are the smallest unit of matter, and atoms themselves are made of subatomic particles – protons, neutrons, and electrons.
Matter can take the form of a solid, liquid, or gas. This all depends on how closely the atoms in matter are packed together. In a solid, the atoms are locked in place, touching each other and vibrating slightly. In a liquid, the molecules are touching but they can move around. In a gas, atoms rarely meet. Instead, they are busy flying around each other at a high velocity.
There are four basic properties of matter that help us describe different objects and substances: volume, mass, density, and weight.
Volume
Matter takes up space. This is called volume. You can measure the volume of a liquid like water by pouring it into a measuring cup. You can measure the volume of a rectangular solid by measuring the sides and multiplying. One way that scientists measure the volume of a gas is by measuring how much liquid a gas can displace.
Mass
Mass is a measure of the amount of matter in an object. The more mass an object has, the stronger its gravitational pull. The Earth has much more mass than the Moon, so it has much stronger gravity. That’s why the Moon rotates around the Earth and not the other way around!
Weight
Weight is similar to mass because it measures how much matter a substance is made of. However, weight is a measure of the amount of force being exerted on an object by gravity. Since gravity is different on different planets, weight is not fixed.
The weight of an object is relative to the amount of gravity. Since the Moon has weaker gravity than Earth, a rock weighs less on the moon. However, the rock has the same mass on both the Moon and the Earth. Mass measures the amount of stuff in the rock – the number of atoms – and that hasn’t changed. But, the force pulling downward on the rock has changed – that determines the weight.
Density
Think about a rock and a foam replica of the same rock. While they both take up the same volume, they have a very different mass. The real rock has a much higher mass, while the foam rock is much lighter and has less total mass. These two objects have a different density. Density is a measure of how tightly packed the atoms in an object are.
Written by Laura McCamy
Edited by Gabriel Buckley, MS Professional Natural Sciences
Illustrated by Pablo Velarde Diaz-Pache