# Gas Lesson for Kids: Definition & Facts

Instructor: Anna Reinking

Anni taught elementary school for eight years and is currently teaching college. She received her Ed.D. in Curriculum and Instruction.

This lesson will discuss one of the three states of matter known as gas. This lesson will discuss the definition of gas, examples of gases, and other interesting facts about this state of matter.

## What Is Gas?

Gas is one of the three states, or forms, of matter and is invisible. Matter is anything that takes up space. Basically, gas is one of the ways matter can take up space and is related to the branch of science called physics.

Have you ever seen a balloon floating up into the air? That balloon is filled with helium, which is a type of gas that's lighter than the air around it, causing the gas to push its way upward, bringing the balloon with it.

Or, have you even seen or felt steam rise from a boiling pot of water? That steam is also gas. Gas is all around us. It is even in the air we breathe.

Additionally, when you hear people talking about gases, you may also hear the term vapor. In general, vapor and gas refer to the same state of matter. However, when people use the term vapor, they are usually referring to something that is liquid at room temperature, such as steam.

## How Gas Behaves

States of matter are made up of atoms, tiny particles that make up molecules, which make up matter. Depending on the temperature and pressure of the environment, molecules behave differently. In a gas, the molecules expand to fill up the entire size of the container it's in, whether that's a bottle or an entire room. No matter the size of the container, the molecules in a gas will spread equally throughout the entire container.

The atoms inside the molecules move faster and further away from one another, compared to other states of matter. Here's a helpful way to think of atoms and molecules in gas: Atoms and molecules have space to move around in gas, and when they move, they create energy and heat. It gets so hot that the atoms and molecules want to get away from each other, just like people need their space to stay cool on a hot summer day. So, they spread out as far as they can.

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