Solids, liquids and gases

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Lesson notes

The Particle Model

All matter is made of **particles** (atoms or molecules).
The three states of matter are **solid**, **liquid**, and **gas**.
Properties depend on particle arrangement and movement.

Solids

Particles are held **tightly together** in a **regular pattern**.
Particles **vibrate** around fixed positions.
Solids have a **definite shape** and **definite volume**.
They are **dense** and **cannot be compressed** easily.
Solids have the **least amount of energy**.

Liquids

Particles are **close together** but can **move past each other**.
Liquids have a **changing shape** (they flow) but a **fixed volume**.
They are **dense** and **cannot be compressed** easily.
Liquids have **more energy** than solids.

Gases

Particles are **far apart** with **very weak forces** between them.
Gases have **no fixed shape** and **no fixed volume**.
They can be **compressed** and have **low density**.
Particles move **quickly in random directions** at different speeds.
Gas pressure is caused by particles **colliding** with container walls.
Gases have the **most energy**; heating increases particle speed.

Density and Water Exception

Solids are usually the **most dense** state.
**Water** is an exception: liquid water is **more dense** than ice (solid).
Ice floats because it is **less dense** than liquid water.

Particle arrangement in solids, liquids, and gases.

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Practice questions

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1.Which state of matter has particles that are held tightly together in a regular pattern and vibrate around fixed positions?
Easy
- ASolid
- BLiquid
- CGas
- DPlasma
2.Which state of matter can be compressed?
Easy
- ASolid
- BLiquid
- CGas
- DBoth solid and liquid
3.Which state of matter has a definite shape and volume?
Easy
- ASolid
- BLiquid
- CGas
- DNone of the above
4.Which state of matter has the most energy?
Easy
- ASolid
- BLiquid
- CGas
- DAll have the same energy
5.Why does ice float in water?
Medium
- AIce is denser than water
- BIce is less dense than water
- CIce has a higher temperature than water
- DIce has more particles than water
6.What happens to the speed of gas particles when the temperature of a gas is increased?
Medium
- AThey move more slowly
- BThey move more quickly
- CThey stop moving
- DThey move at the same speed
7.Which of the following correctly describes the movement of gas particles?
Medium
- AThey vibrate in fixed positions
- BThey move slowly in the same direction
- CThey move quickly in random directions
- DThey slide past each other
8.A student observes that a substance has no fixed shape but has a fixed volume. Which state of matter is it?
Hard
- ASolid
- BLiquid
- CGas
- DPlasma

Revision notes

## Solids, Liquids and Gases All matter is made of particles (atoms or molecules). The three states have different properties due to particle arrangement and movement. ### Solids - Particles held **tightly together** in a regular pattern. - Vibrate around **fixed positions**. - **Definite shape** and **volume**. - Cannot be compressed easily. - **Dense** (but water/ice exception: ice less dense than water). - **Least energy**. ### Liquids - Particles close together but can **move past each other**. - **Changeable shape**, can flow. - **Fixed volume**. - Cannot be compressed easily. - **Dense**. ### Gases - **Very weak forces** between particles, which are **far apart**. - Particles move **quickly in random directions** at different speeds. - **No fixed shape or volume**; can be compressed. - **Low density**. - **Most energy**. - Pressure from particles colliding with container walls. - Heating increases particle speed. ### Key Points - **Compressible**: gas only. - **Shape change but fixed volume**: liquid. - **No fixed volume**: gas. - **Low density**: gas. - **Vibrate around fixed positions**: solid. - **Particles flow but close**: liquid. - **Ice floats** because water is denser than ice (exception). - **Gas particle speed increases** with temperature. - **Gas particles move** quickly in random directions. - **Solid to liquid**: particles gain energy, break free from fixed positions, can move past each other but remain close. - **Liquid to gas**: particles gain more energy, overcome forces, move far apart and quickly.

Solid: State of matter with particles held tightly together in a regular pattern, vibrating around fixed positions; has definite shape and volume.
Liquid: State of matter with particles close together but able to move past each other; has fixed volume but changes shape.
Gas: State of matter with particles far apart, moving quickly in random directions; no fixed shape or volume, can be compressed.
Compress: To reduce the volume of a substance by squeezing particles closer together; gases can be compressed easily.
Density: Mass per unit volume; solids and liquids are usually dense, gases have low density.
Particle: An atom or molecule that makes up matter.
Pressure: Force exerted by gas particles colliding with the walls of a container.

Flashcards

What are the three states of matter?

Solid, liquid, and gas.

What is the particle arrangement in a solid?

Particles are held tightly together in a regular pattern and vibrate around fixed positions.

What is the particle arrangement in a liquid?

Particles are held closely together but can move past each other.

What is the particle arrangement in a gas?

Particles are far apart with very weak forces between them, moving quickly in random directions.

Which state of matter has a definite shape and volume?

Solid.

Which state of matter can be compressed?

Gas.

Which state of matter can change its shape but not its volume?

Liquid.

Which state of matter has no fixed volume?

Gas.

Which state of matter has a low density?

Gas.

Which state of matter has particles that vibrate around fixed positions?

Solid.

Which state of matter is used in hydraulics?

Liquid.

Which state of matter has particles that flow but are still close together?

Liquid.

What happens to the speed of gas particles when the temperature of a gas is increased?

The particles move more quickly.

Describe the movement of gas particles.

They move around quickly in random directions at a range of different speeds.

How does particle arrangement change when a solid becomes a liquid?

The particles remain close together but can move past each other, losing the regular pattern.

How does particle arrangement change when a liquid becomes a gas?

The particles move far apart and move quickly in random directions.

Why do ice cubes float in water?

Water (liquid) is more dense than ice (solid).

Which state of matter has the least energy?

Solid.

Which state of matter has the most energy?

Gas.

What causes gas pressure?

Particles colliding with the walls of a container.

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