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Science!Science!
All substances are made from atoms or molecules (atoms joined together),
also known as particles. The way that these particles move around determines whether
the substance is a solid, liquid or gas.
Solids
In a solid, the
particles are touching
and packed closely
together. They are
xed and cannot move.
The properties of solids include:
• A solid stays in one place and can
be held.
• Solids can be cut or shaped.
• Solids keep their shape and volume
and do not ow like liquids.
• Solids take up the same amount
of space and do not spread out
like gases.
• Even though they can be poured,
salt, sugar and our are all solids.
Each particle keeps the same
shape and volume.
Liquids
In a liquid, the
particles are mainly
touching, but some
gaps have appeared
in the structure.
These gaps allow
the particles to move, and so the
particles are arranged randomly.
The properties of liquids include:
• Liquids can change their shape
depending on the container they
are in.
• Liquids can ow or be poured
easily. They are not easy to hold.
• Even when liquids change their
shape, they always take up the
same amount of space and their
volume stays the same.
Gases
In a gas, the particles
are widely spaced
and entirely free to
move. They can whizz
around at high speed.
The properties of
gases include:
• Gases do not have a
xed shape.
• Gases can spread out and change
their shape and volume to ll up
whatever container they are in.
• Gases are often invisible.
• Gases can be squashed.
Solids, liquids and gases are called the
three states of matter.
Changing states of matter
Evaporation and condensation
Liquids and gases can be changed from one state to
another by heating or cooling.
Heat can turn a liquid into a gas, and cooling can cause a
gas to turn into a liquid.
Heating – fresh water boils at 100°C.
If water (liquid) is heated, it changes to water
vapour (gas). This change is called evaporation.
Cooling
If water vapour (gas) is cooled down, it changes into
water (liquid). This change is called condensation.
Freezing and melting
Solids and liquids can be changed from one state to
another by heating or cooling.
Heat melts a solid and turns it into a liquid. Cooling
freezes a liquid into a solid.
Heating
If ice (solid) is heated, it changes to water (liquid). This
change is called melting.
Cooling – fresh water freezes at 0°C.
If water (liquid) is cooled, it changes to ice (solid).
This change is called freezing.
