1.3Chapter 1: The Particle Model and States of Matter

Using the particle model — Alhussan Chemistry - Stage 7 Revision Notes & Topical Questions

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1.3 Using the particle model — Explaining Compression, Flow and Shape — Alhussan International Academy — Chemistry (Stages 7–9) notes: Use the particle model to explain why solids, liquids and gases differ in shape, flow and compressibility, and define a vacuum.Basic idea — all m…

Solids and liquids
Aerosol cans
Scuba and firefighters' cylinders
Hydraulic jacks and brakes
Bicycle pumps
Change of state

Section 1 of 10The particle model of three states

The particle model of three states

Basic idea

Basic idea all matter is made of tiny particles that are always in motion.
The state depends on how the particles are arranged and how strongly they attract each other.

Solid

Solid particles touch in a regular pattern, hold together strongly and vibrate about fixed positions.

Liquid

Liquid particles touch in a random arrangement and move past one another.

Gas

Gas particles are far apart, move quickly in random directions and have very weak forces between them.

Section 2 of 10Explaining shape

Solid

Solid it keeps its own shape because its particles are held in fixed positions by strong forces.
Solid carbon dioxide (dry ice) lumps keep their shape and size if kept cold.

Liquid

Liquid it has a fixed volume but takes the shape of its container, because particles slide over each other but stay in contact.
The shape of liquid water keeps changing when a child pours it from jar to jar.

Gas

Gas it spreads out to fill any container, because particles move freely and the forces between them are too weak to hold them in one place.
Carbon dioxide gas spreads out and mixes with the air all around the Earth.

Section 3 of 10Explaining flow

1Fluids

Fluids liquids and gases are called fluids because their particles move from place to place, so they can flow.
Liquid mercury flows and carbon dioxide flows in the gas state.

2Solids

Solids a solid cannot flow because its particles are in fixed positions and cannot change places.
Solid mercury and solid carbon dioxide cannot flow.

3Powders

Powders sand seems to pour, but each grain is a tiny solid.
The grains slide over one another and the particles inside each grain are still locked in place.

Section 4 of 10Explaining compression

Compress

Compress to squeeze a substance into a smaller volume, which is only possible if there is empty space between particles.

Gases

Gases all substances can be compressed in the gas state, because the particles are far apart and get closer together when squeezed.
The particles themselves stay the same and do not change size.
The oxygen in a firefighter's cylinder would normally fill about 1000 soda bottles.

Solids and liquids

Solids and liquids they can be compressed only a very tiny bit, because their particles are already touching.

Section 5 of 10Comparing the states

Property	Solid	Liquid	Gas
Shape	Fixed	Takes container shape	Fills container
Can flow	No	Yes	Yes
Compressible	No	Almost not	Yes
Density	High	High	Low

Section 6 of 10Vacuum

Vacuum = a space that has no particles and so no matter.
- Most of outer space is close to a vacuum, though a few particles are very far apart.

Section 7 of 10Everyday applications

1Dry ice

Dry ice solid carbon dioxide packed around vaccine bottles keeps them very cold.

2Aerosol cans

Aerosol cans they hold gas squeezed into a small volume, and the particles spread out when the valve opens.

3Scuba and firefighters' cylinders

Scuba and firefighters' cylinders many gas particles are packed into a small container.

4Hydraulic jacks and brakes

Hydraulic jacks and brakes liquid cannot be compressed, so a force applied at one point is passed on through the liquid to another point.

5Bicycle pumps

Bicycle pumps they use air, which is easily compressed.

Section 8 of 10Giving a full explanation

State the property, describe the particle arrangement and movement, then link the two.

Change of state

Change of state the particles themselves stay the same, and only the arrangement, spacing and energy change, so the mass is unchanged.

Section 9 of 10Key terms

Term	Meaning
Vacuum	A space with no particles and so no matter.
Fluid	A substance that can flow: a liquid or a gas.
Compress	To squeeze into a smaller volume.
Dry ice	Solid carbon dioxide.
Particle model	A model describing the arrangement and movement of particles.
Flow	Movement of a substance from place to place as its particles move around.