Density
Physics: Cambridge International A Level, topic 4.1.12
Density
Density is a measure of how much mass an object has per unit volume.
Density
- Density is a measure of how much mass an object has per unit volume.
- Density can be used to determine how heavy an object is based on its volume.
Calculating density
- Density can be calculated using the formula:
- ρ =
- ρ (Rho) is the density of the material.
- m is the mass of the object.
- V is the volume of the object.
Units of density
- Density will be measured in a unit which specifies mass divided by volume:
- The most common is kgm-3 (kilograms per cubic metre).
Density - Example
The baby elephant has a higher density than water. So the baby elephant sinks.
Baby elephant
Calculating Density
To find out the density (density=mass/volume) of an object, we measure its mass and volume. We can measure the mass of an object using a balance (scales). We can calculate the density of:
Liquids
- To measure the density of liquids, place a measuring cylinder on a balance and set the reading to zero.
- Pour the liquid into the cylinder and write down its mass and volume. Then calculate the density.
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Irregularly shaped solids
- For solids, we can use the Law of Displacement to estimate its volume.
- This is done using a displacement can, or a graduated measuring cylinder.
- The volume of displaced water is measured, and this is the volume of the object.
Test yourself on Density
Which of these is a common unit for density?
What is a correct unit for density?
If the mass is 10 kg and volume is 2.5 meters cubed, what is the density of the object?
Ice has a lower density than water. This means that it should float in water. Steel has a density significantly higher than water. However, a steel ship still floats. Suggest how this is possible.
What is the law of displacement?