What is diffusion?
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Diffusion is said to have
occurred when chemicals mix
together without anything
moving them.
What is particle theory?
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Diffusion occurs because
particles in a substance are
always moving around.
Diffusion is fastest in gases,
and slower in liquids.
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The different properties of solids, liquids and gases can be
explained by the particle theory (or particle model).
Solids, liquids and gases (the three states of matter) need
to be handled and stored differently because of these
different properties.
The properties of a solid.
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Key words:
What is pressure?
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Pressure is caused by
particles hitting the walls of
the container they are in.
Diffusion occurs because
particles in a substance are
always moving around.
Diffusion is fastest in gases,
and slower in liquids.
The pressure may increase
because:
• the container has been
squashed, making the volume
smaller so that the particles
will be hitting the walls more
often.
• the number of particles has
been increased, so that
there are more particles
moving around to hit the
walls.
1.
2.
3.
Gas: Something that does not have a fixed shape or volume, and is easy to squash.
Liquid: Something with a fixed volume but no fixed shape
Property: A description of how a material behaves and what it is like. Hardness is a property of
some solids.
4. Solid: Something with a fixed shape and volume. .
5. States of matter: There are three different forms that a substance can be in: solid, l
6. Volume: The amount of room something takes up. Often measured in cubic centimetres (cm3 ).
7. Particle Theory: Theory used to explain the different properties and observations of solids,
liquids and gases.
8. Particles: The tiny pieces that everything is made out of.
9. Diffusion: When particles spread and mix with each other without anything moving them.
10. Air Pressure: The force on a certain area caused by air molecules hitting it.
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The
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Liquids are made up of particles
that are fairly close together.
(Quite strong forces of attraction
hold the particles together.)
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The particles in liquids are able to
move past each other.
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Liquids have a fixed volumes but
their shape can change to fit the
container as they flow easily.
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Liquids cannot be easily
compressed (squashed).
The properties of a gas.
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Gases are made up of particles that are well spread out. (There are only
weak forces of attraction between the particles.)
The particles in gases move about freely in all directions.
The shape and the volume of gases can change as they flow very easily
and spread out.
Gases can be compressed (squashed) quite easily.
Solids are made up of particles
that are very close together.
(Strong forces of attraction hold
the particles together.) Opaque
surfaces can absorb or reflect
light.
The particles in solids vibrate in
fixed positions.
The shape and volume of solids do
not change.
Solids cannot be squashed and do
not flow.
properties of a liquid.
Revision Questions
1. Draw particle diagrams of solids liquids and gases.
2. Add arrows to your diagrams to show where evaporation,
melting, freezing and condensation take place. For each of
these keywords, write a definition next to the arrow.
3. State 2 properties of solids, 2 of liquids and 2 of gases.
4. Now explain why the materials have these properties. E.g.
“Solids are _____ because…”
5. Explain what diffusion is and how it happens. Include a
particle diagram in your answer.
6. What causes pressure? Give an examples of things you would
describe as high pressure and low pressure.
7. The brakes in a car rely on pipes full of liquid – why would it be
an issue if air got in to these pipes?
Revision Questions
1. Draw particle diagrams of solids liquids and gases.
2. Add arrows to your diagrams to show where
evaporation, melting, freezing and condensation take
place.
3. State 2 properties of solids, 2 of liquids and 2 of
gases.
4. Now explain why the materials have these properties.
E.g. “Solids are _____ because…”
5. You can smell food cooking across a room because of
diffusion. Explain what diffusion is and how it happens.
Include a particle diagram in your answer.
6. What causes pressure? Give an examples of things you
would describe as high pressure and low pressure.