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Discovering chemistry
Discovering chemistry

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1.1 Units of volume

The SI unit of volume is the cubic metre (m3), but this is too large for the types of volumes laboratory chemists generally work with; litres, l (or cubic decimetres, dm3) are used instead, where 1 l = 1 dm3.

But what does 1 litre (or 1 dm3) of fluid look like? What about a millilitre (ml, one thousandth of a litre) or a microlitre (µl, one millionth of a litre)?

A litre is the volume of liquid (or gas) that would fit into a cube measuring 10 cm (or 1 dm) on each side: 10 cm × 10 cm × 10 cm = 1000 cubic centimetres (cm3) = 1 litre.

A millilitre is the volume of a cube measuring 1 cm on each side: 1 cm × 1 cm × 1 cm = 1 cm3 = 1 ml.

A microlitre is the volume of a cube measuring 1 mm on each side: 1 mm × 1 mm × 1 mm = 1 mm3 = 1 µl.

To help you visualise these volumes, consider the following:

A typical carton of fruit juice has a capacity of 1 litre.

A teaspoon holds about 5 ml of liquid.

One raindrop is about 30 µl.

  • Express 2 µl in litres.

  • 2 µl = 2 × 10−6 l