Question
Explain the term density, giving its units and dependence on temperature and pressure.
✓
Answer
Density is defined as the mass present in a unit volume of a substance.
Density $=\frac{\text { Mass }}{\text { Volume }}$
The units in which density is expressed will depend upon the units of mass and volume.
If the units of mass and volume are kilogram (kg) and cubic metre (m3) respectively.
The SI unit of density is kilogram per cubic metre (kg/m3).
For liquid units of density is used in grams per milliliter (g/mL).
The density of a substance is independent of its shape and size but depends on temperature and pressure. The effect of pressure on the density of solids and liquids is negligible, but the density of gases decreases. If we compare the density of two substances, it is called relative density. It is a number without units. For example, the mass of an aluminium block is 27 g and its volume is 10 cm3,so its density is 2.7 g/cm3. But its relative density with respect to water is 2.7, i.e., it is 2.7 times heavier than water.
Density $=\frac{\text { Mass }}{\text { Volume }}$
The units in which density is expressed will depend upon the units of mass and volume.
If the units of mass and volume are kilogram (kg) and cubic metre (m3) respectively.
The SI unit of density is kilogram per cubic metre (kg/m3).
For liquid units of density is used in grams per milliliter (g/mL).
The density of a substance is independent of its shape and size but depends on temperature and pressure. The effect of pressure on the density of solids and liquids is negligible, but the density of gases decreases. If we compare the density of two substances, it is called relative density. It is a number without units. For example, the mass of an aluminium block is 27 g and its volume is 10 cm3,so its density is 2.7 g/cm3. But its relative density with respect to water is 2.7, i.e., it is 2.7 times heavier than water.
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