Density
Density is the mass per unit volume.
Density can be found using this equation.
\(\text{density}=\frac{\text{mass}}{\text{volume}}\)
\(\text{\rho}=\frac{\text{m}}{\text{v}}\)
The unit for density is kg/m3. The density of water is approximately 1,000 kg/m3 and the density of air is approximately 1.2 kg/m3.
Density is sometimes measured in g/cm3. Make sure that you use units that are consistent with the question in an exam.
Measuring density
To measure the density of a regular shaped solid you must measure the sides of the object, and calculate its volume.
\(\text{volume =}~{\text{length}}\times{\text{height}}\times{\text{width}}\)
Record the mass of the object, calculate its density using this equation.
\(\text{density}=\frac{\text{mass}}{\text{volume}}\)
If the object is an irregular shape, we need to place the solid into a cylinder of water and record the increase in the volume in order to calculate the volume of the object.
The mass of the object can be recorded and the density calculated using this equation.
\(\text{density}=\frac{\text{mass}}{\text{volume}}\)
This diagram shows why the densities of solids tend to be greater than liquids and why the density of liquids is greater than gases.