Mass per unit volume density
Mass per unit volume density
Mass per unit volume density – A solid object has a volume of 60 cm3. If the mass of this solid is 600 grams (g) then, by proportion,
1 cm3 has a mass of 600 g/60 cm3=10 gram per cm3 (10 g/cm^3)
Since 1 cm3 is unit volume in this instance, then the mass per unit volume of the solid shown is 10 g/cm3. Mass per unit volume of any body is also called the density of that body. The symbol for density is the Greek letter ‘rho’ (ρ).
The general expression for mass per unit volume (density) is:
ρ=m/V
where:
ρ=density
m=mass
V=volume
The densities of some common solids, liquids and gases used in engineering are given in below:
| Density of common substances | ||
| Substance | Density | |
| kg/m3 | g/cm3 | |
| Aluminium | 2720 | 2.72 |
| Brass | 8480 | 8.48 |
| Copper | 8790 | 8.79 |
| Cast iron | 7200 | 7.20 |
| Lead | 11350 | 11.35 |
| Nylon | 1120 | 1.12 |
| PVC | 1360 | 1.36 |
| Rubber | 960 | 0.96 |
| Steel | 7820 | 7.82 |
| Tin | 7280 | 7.28 |
| Zinc | 7120 | 7.12 |
| Alcohol | 800 | 0.80 |
| Mercury | 13590 | 13.59 |
| Paraffin | 800 | 0.80 |
| Petrol | 720 | 0.72 |
| Water (pure at 4°C) | 1000 | 1.00 |
| Acetylene | 1.17 | 0.0017 |
| Air (dry) | 1.30 | 0.0013 |
| Carbon dioxide | 1.98 | 0.00198 |
| Hydrogen | 0.09 | 0.00009 |
| Nitrogen | 1.25 | 0.00125 |
| Oxygen | 1.43 | 0.00143 |