Calculating density
Density also depends on the material. A piece of iron with the same dimensions as a piece of aluminium will be heavier because the atoms are more closely packed.
Scientists can find the density of a material by measuring the mass of a certain volume of the material, for example, one cubic centimetre.
| Material | Density in grams per cubic centimetre (g/cm鲁) |
| Iron | 7.8 |
| Ice | 0.98 |
| Water | 1 |
| Air | 0.00129 |
| Material | Iron |
|---|---|
| Density in grams per cubic centimetre (g/cm鲁) | 7.8 |
| Material | Ice |
|---|---|
| Density in grams per cubic centimetre (g/cm鲁) | 0.98 |
| Material | Water |
|---|---|
| Density in grams per cubic centimetre (g/cm鲁) | 1 |
| Material | Air |
|---|---|
| Density in grams per cubic centimetre (g/cm鲁) | 0.00129 |
Calculating density
Density can be calculated using the equation:
\(density = \frac{mass}{volume}\)
\(\rho = \frac{m}{V}\)
This is when:
- density (蚁) is measured in kilograms per metre cubed (kg/m3)
- mass (m) is measured in kilograms (kg)
- volume (V) is measured in metres cubed (m3)
Example
What is the density of a material of 0.45 cubic metres (m3) if it has a mass of 0.2 kg?
\(\rho = \frac{m}{V}\)
\(\rho = \frac{0.2}{0.45}\)
\(\rho = 0.44~kg/m^{3}\)
The units for density
Although the standard unit for mass is kilograms (kg) and for volume is cubic metres (m3), in many laboratory situations the norm is finding the mass in grams (g) and volume in cubic centimetres (cm3).
Calculating density using grams and centimetres cubed would give a density unit of grams per centimetre cubed (g/cm3).
Question
What is the density of a material of 15 cm3 if it has a mass of 30 g?
\(\rho = \frac{m}{V}\)
\(\rho = \frac{30}{15}\)
\(\rho = 2~g/cm^{3}\)
Aluminium has a density of 2.7 g/cm3, or 2,700 kg/m3. Lead has a density of 11.6 g/cm3, or 11,600 kg/m3.