Properties of Matter

Measuring the density of water 2

Practical Activity for 14-16 PRACTICAL PHYISCS

If the pan size is such that the 1 kg mass might fall off, place an open cardboard box below the pan to catch it.


This method uses an equal-arm balance rather than a domestic spring balance.

Apparatus and Materials

  • Equal-arm balance
  • Perspex boxes with internal dimensions 10 cm x 10 cm x 11 cm, 2
  • Mass, 1 kg

Health & Safety and Technical Notes

Read our standard health & safety guidance

The boxes should have horizontal marks, on one face, 10 cm above their internal bases.


  1. Place a box on each scale pan to show that they balance.
  2. Add the kilogram mass to one pan and carefully pour water into the box on the other pan until the beam balances. The water will then be seen to have a depth of 10 cm, and so a volume of 1000 cubic centimetres and a mass of 1 kg .

Teaching Notes

  • An alternative is to measure out a kilogram of water and show it has a volume of 1000 cubic centimetres (1 litre).
  • A metre cube could be used to help students see that the mass of a cubic metre of water would be 1000 times greater.

This experiment was safety-tested in July 2006

appears in the relation m=ρV
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