# 3 States of Matter Explained: Solids, Liquids, and Gases

Updated on: Educator Review By: Michelle Connolly

Everything in our world (and the whole universe) exists in one of three states. These three states are solids, liquids, and gases. So, what are these states? They are the states of matter.

If you look around, you will likely see one of these three states or all three. The screen you are looking at is solid, your blood is liquid, and the air you breathe is gas. See? They are everywhere!

In this lesson, we are going to learn everything about solids, liquids, and gases. Let’s start with defining the matter.

## What is Matter?

Everything on our planet that we can see, touch, or feel is made up of matter. It is part of anything that we use on a daily basis, including the air we breathe.

The matter is made up of millions of tiny objects called atoms and molecules. These objects fit together to form larger objects like sand, cars, water, and planets. Atoms and Molecules are, in turn, made up of protons and electrons.

## States of Matter

The air we breathe, the books we read, and the water we drink are all examples of matter. So, matter on Earth comes in three different forms (or states): solids, liquids, and gases.

## Solid

Solids are matters that can hold their shape.

When the matter is in a solid state, its molecules are tightly packed together and arranged in a regular pattern. Because of this, the electrons’ movements become so limited that they can hardly move at all, which is why solids are usually hard.

Solids come in different physical properties. They can be soft like silk or hard like a rock. They don’t have a specific size; some are small, like a grain of sand, or huge, like a planet.

### Characteristics of Solids

• Solids hold a fixed shape and volume, so they don’t move to fill the space when placed in a container.
• Solids occupy space.
• Solids can be weighed to find out their heaviness.
• Compressing a solid into a smaller area is difficult because the atoms are tightly packed.

## Liquid

Liquids are matters that can flow or run, but they cannot be compressed or stretched.

When a matter is in a liquid state, its molecules are packed closely but not as tightly as solids. These molecules can move around and slip past one another since they are not arranged in any particular pattern. That is how liquids change their shape.

### Characteristics of Liquids

• A liquid does not hold a fixed shape but has a fixed volume. So, when placed in a container, it spreads out to fill it, yet it keeps its own volume intact.
• Like solids, liquids occupy space.
• Like solids, liquids can be weighed to find out their heaviness.
• Compressing a liquid into a smaller area is difficult because there is a small amount of space between the atoms.

## Gas

Gases are matters that can flow, expand, or be compressed, and they don’t have a fixed shape or volume.

When a matter is in a gas state, its molecules are widely dispersed further apart. These molecules can move around in various directions, in any space, and very quickly. That is why gases don’t have a fixed shape.

### Characteristics of Gases

• Gases don’t have a fixed shape or volume. So, they fill the space when placed in a container.
• Like solids and liquids, gases occupy space and can be weighed even though they are often invisible.
• Compressing gas into a smaller area is possible because its molecules are quite far apart.

## Changing States

We have learned that matter is made up of atoms and molecules. When the state of matter changes, the atoms and molecules do not change, but the way they move and act does. For example, water can change states, liquid, solid (ice), or gas (water vapour), but it always consists of the same atoms (one oxygen atom and two hydrogen atoms).

The state of matter can change by applying or removing only two factors, pressure and heat. Changes in heat and pressure cause the movement and arrangement of the molecules to change, which, in turn, changes the state of matter.

Rising a liquid matter’s temperature causes its molecules to move fast and apart to the point where they become loose and spread, causing the state of the matter to change into a gas. Reducing a liquid matter’s temperature causes its molecules to slow down to the point where they become packed together, causing the state of the matter to change into solid ice.

So, matter can change states depending on its temperature. When heated, liquid water turns into gas; when cooled down, it turns into solid ice. When solid ice is heated, it turns into liquid water; when water vapour is cooled down or condensed, it turns into liquid water.

## Methods of Changing States

There are mainly four methods through which matter states can change.

1) Melting

It is the transformation of a solid into a liquid.

2) Evaporation

It is the transformation of a liquid into a gas.

3) Condensation

It is the transformation of a gas into a liquid.

4) Freezing

It is the transformation of a liquid into a solid.

Some solids can turn directly into gases without melting first, such as dry ice, which is essentially solid carbon dioxide.

## How Does Matter Change Its State?

There are two types of changes in the state of matter:

### A Reversible Change

It is the change of state that can be changed back. For example, we can turn ice into liquid water by melting it and turn the liquid water back into ice by cooling it down.

### An Irreversible Change

It is the change of state that cannot be changed back. A change becomes irreversible when a chemical reaction happens. For example, baking a liquid cake mixture turns it into a solid cake that cannot be changed back into liquid.

## More States of Matter

There are two more states of matter that are not often seen in our daily life.

The first is plasma. It is a matter that forms at extremely high temperatures. Plasma is found in stars and lightning bolts.

The other state is called Bose-Einstein Condensates. It is a matter that forms at extremely low temperatures. It can be found only in a lab where temperatures are very reduced.

## Interesting Facts about Solids, Liquids, and Gases

• Plasma is the most widespread state of matter in the universe because stars are primarily composed of plasma.
• The air that humans breathe is mainly made of oxygen, nitrogen, and other gases.
• Fire is made up of hot gases.
• Burning liquid gasoline in cars produces many gases that escape through the exhaust pipe.
• Some solids, like glass, are transparent, and we can see through them.

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