2. What instrument(s) would you use to measure mass? 3. What instrument(s) would you use to measure volume?
The density of a substance is its mass divided by its volume. The SI unit for density is g/cm3 density = EXAMPLE
Question Calculate the density of a cube with a mass of 200 g and a volume of 64 cm3
Solution density =
density = mass volume
200 g 64 cm3
density = 3.1 g/cm3 . mass volume or kg/m3 .
To calculate the density of an object, you must first know its mass (measured in g or kg) and its volume (measured in cm3
CONCENTRATE! The following triangle is a useful tool for remembering the formulae for calculating mass, volume and density. Simply cover the quantity you want to measure with your finger and use the formula that you can still see.
mass density × volume
CONCENTRATE! Using the SI units throughout a calculation makes them easier to remember. Always include the units in your answer.
FIGURE IT OUT!
1. A wooden fencepost has a volume of 0.02 m3 2. Aluminium has a density of 2700 kg/m3
254 Elements of Science
and a mass of 18 kg. Calculate its density in kg/m3 . Calculate the volume of 240 g of this metal.