Density

This lesson covers the concept of density as required by the AQA GCSE Combined Science Trilogy specification (8464, section 6.3.1). Density links the mass of a substance to the volume it occupies and is essential for understanding why some objects float and others sink.

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What Is Density?

Density is defined as the mass per unit volume of a substance. It tells you how much matter is packed into a given space.

$\rho = \frac{m}{V}$ρ=Vm​

Symbol	Quantity	Unit
$\rho$ρ (rho)	Density	kilograms per cubic metre (kg/m³) or grams per cubic centimetre (g/cm³)
$m$m	Mass	kilograms (kg) or grams (g)
$V$V	Volume	cubic metres (m³) or cubic centimetres (cm³)

Exam Tip: The density equation is one of the equations you must recall from memory — it is NOT given on the AQA equation sheet. Make sure you can write it from memory: $\rho = m / V$ρ=m/V.

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Rearranging the Density Equation

You must be able to rearrange the equation to find any quantity: