STATES OF MATTER
DENSITY
Learning Points
• Explain the different masses of
materials with the same volume in
terms of particle spacing and relate
this to density.
Density
Take a look at the two boxes below. Each box
has the same volume.
If each ball has the same mass, which box would
weigh more? Why?
The box that has more balls has more mass
per unit of volume.
This property of matter is called DENSITY.
Density
Density is a measure of how many particles of a
substance are in a given area/volume.
It can be worked out using the following
equation.
Density =
mass (g)
volume (cm3)
Solids are usually the most dense, followed by
liquids and then gases.
Density of Liquids
Like solids, different liquids have different
densities.
Less dense liquids float on more dense liquids.
Oil is less dense than
water and will float on top
of it.
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EXPERIMENT
AIM:
Calculate the density of three different
liquids.
INSTRUCTIONS
1. Draw out the following table.
LIQUID
WATER
VEGETABLE
OIL
GLYCEROL
VOLUME (cm3)
MASS (g)
Density of liquids
INSTRUCTIONS
1. Put a 100ml measuring cylinder on an
electronic balance and zero it.
2. Pour in 50mls of water into the cylinder
and write down the mass shown on the
balance.
3. Calculate the density by dividing this mass
by 50cm3.
4. Repeat for the other two liquids.
WHAT DID YOU FIND
OUT?
Density of gases
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Hot air is less dense than cold air
Hot air rises
Density of gases
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The particles in cold air are closer together and
so it is denser than hot air.
EXPERIMENT
AIM: Changing the density of a substance.
INSTRUCTIONS
1. Draw out the following table.
TYPE OF LIQUID
WATER
WATER + DISSOLVED
SALT
DOES THE EGG
FLOAT OR SINK?
INSTRUCTIONS
2. Fill a large beaker with water.
3. Carefully place an egg into the water and
see if it floats or sinks.
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INSTRUCTIONS
2. Take the egg out of the glass, add 6
dessert spoons of salt to the water.
Stir it until all the salt has dissolved.
You have made a salt solution.
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3. Carefully place an egg into the salt
solution and see if it floats or sinks.
WHAT DID YOU FIND
OUT?
QUESTIONS
• Can you describe and explain what
happened to the egg when it was placed
in the water?
• Can you compare the density of the egg
and the density of the water.
• What happened to the egg when it was
placed in the salt solution ?
EXPLANATION
• The egg has a LOWER DENSITY
than the water and so FLOATS.
• Adding the salt changes the water
into a salt solution.
• The egg has a HIGHER DENSITY
than the salt solution and so SINKS.