# Measuring the density of water 2

Practical Activity for 14-16

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.

**Demonstration**

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.

Procedure

- Place a box on each scale pan to show that they balance.
- 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*