Simple Particle Theory: Lesson for Kids

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  • 0:04 What's the Matter?
  • 0:45 Moving Particles
  • 2:55 Lesson Summary
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Lesson Transcript
Instructor: Suzanne Rose

Suzanne has taught all levels PK-graduate school and has a PhD in Instructional Systems Design. She currently teachers literacy courses to preservice and inservice teachers.

Have you ever wondered how solids, liquids, and gases are different? In this lesson, find out what makes them have different properties and what this has to do with the particles that they're made from.

What's the Matter?

Look around you. Everything you see on Earth is made of matter. Scientists use the word 'matter' for anything that takes up space and has mass. Atoms and molecules, the building blocks that make up everything, are made of matter. But, not all matter is the same.

There are three different states of matter on Earth because matter can change! An ice cube is in the state of matter that we call a solid. If you left it on the counter, it would melt into a puddle of water. Now it's in the state of matter called a liquid. If you don't clean up the water, it will eventually evaporate and disappear. When this happens, it's in the state of matter called a gas.

Let's learn more about each one of these states of matter.

Moving Particles

Simple particle theory says that all matter is made up of extremely tiny particles - such as atoms or molecules - that are always moving. Let's see how these particles change from one state of matter to another.


When there isn't much space between the particles in matter, they're packed together very tightly. They can't move around very much, but they do move a little bit. They're very attracted to each other, so they stick close together. This is the state of matter we call a solid. The particles in a solid are arranged in a pattern.

Imagine that we put 100 people in your bedroom. They'd all be so close together that there wouldn't be room to move much, but they could still move without moving their feet. They might be able to shake hands, for example, even if they couldn't walk around. That's how particles in a solid move. They vibrate, or shake, in place, and they move slowly.

Solids have a definite shape that doesn't change. If you had a solid, such as a book, and you put it on the kitchen table and then moved it to your backpack, it would stay the same shape in both places.

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