Welcome to practical physicsPracticle physics - practical activities designed for use in the classroom with 11 to 19 year olds

Measuring the density of water 1


This could be a useful introduction to the idea of density of a liquid.

Apparatus and materials

Perspex box with internal dimensions 10 cm x 10 cm x 11 cm

Domestic balance (2 kg to +/- 2 g is adequate)

Cube, 1 m x 1 m x 1 m (e.g. five squares of Corriflute, 1 m x 1 m, with L-shaped wire links for the vertical edges. The fifth square sits on the top - no base is needed.)

Health & Safety and Technical notes

Read our standard health & safety guidance

The Perspex box should have a horizontal line marked on one face, 10 cm from the internal base so it can be filled to that depth. 
The metre cube could be made out of cardboard, and could be collapsible for ease of storage. 



Perspex box and cardboard cube

a Find the masses of the empty Perspex box and then the box filled to a depth of 10 cm. 

b Place the cardboard cube beside the Perspex box. 

Teaching notes

1 Using cubes will help younger or weaker students make the link with densities found for blocks of solids. They may need reminding that 1000 cubic centimetres = 1 litre. 

2 Having found the mass of 1000 cubic centimetres of water, the metre cube can be used to help students see that the mass of a cubic metre of water would be 1000 times greater. Some may be familiar with the thought that the density of water is 1 g/cm3. This will help them see it cannot be 1 kilogram per cubic metre but rather 1000 kg/m3
3 You could remind students that building materials like sand and gravel are sold in cubic metres and so have to be transported in strong sacks. 

This experiment was safety-checked in July 2006