The substance in one beaker fizzes dramatically, changing colour as it effervesces. A tablet in another beaker gently rises and then sinks again.

“Hey! Look at it now,” says one pupil, avidly watching for changes. “It’s falling apart.” “Our’s has lost its topping,” exclaims a voice from another table. “Why isn’t our’s doing anything at all?” moans someone else. “Oh, wait, yes, it’s beginning to crumble now.”

Who would think such excitement could be generated by the humble washing powder tablet? Jean Asher, Year 5 class teacher at St Augustine’s Church of England Junior School, Peterborough, has used the Ariel Stains and Science Schools Programme for several years.

“The children love any active science and this links everyday experience at home with a science project, so they can see the relevance of what we are doing,” she says. “We discuss how the washing is done in their homes, what sorts of clothes are washed and how they might be stained. That brings in materials needing different temperature washes, and the variety of powders and liquids available.”

Next, the class discusses what properties a washing tablet might have. At what stage of a washing cycle would it be best for the tablet to dissolve? How will it be dispersed? The pupils revise the principles of a fair test and observation before embarking on the experiment.

Tablets of Ariel and Persil are dropped simultaneously into separate beakers of warm water and the reactions recorded. It is the Ariel that froths and fizzes, dissolving almost immediately.

The second half of the programme is demonstrated by Asher, but each child will have a pack to take and try at home.

Ketchup is smeared over some fabric and two Ariel tablets dropped into a beaker of warm water. They dissolve, producing an alarming amount of foam.

Quickly, the ketchup-stained fabric is held tightly over the top of the beaker so that the foam pushes through it, forcing the ketchup to disappear before our eyes. “Cool!” says the group of impressed pupils.

The Ariel pack comes with a helpful teacher’s manual, the necessary beakers, fabric, tablets and ketchup, as well as 30 certificates and a poster for displaying the class’s results.

Children can continue the tests at home, recording number and type of washes over a two-week period to create bar charts. The findings can be used for further discussion about, for example, the impact of washing machines on the environment. The whole project can then be entered into an Ariel competition, with a prize of school sports kits .

“I have adapted the programme sometimes, using paint rather than ketchup to make stains, and organising it so that children can work in pairs rather than at tables,” says Asher.

“Basically, it is a very useful project that reinforces scientific principles in a fun and easy way. But I think two weeks is too long for most children to record family washing - a week is more realistic. I suspect some of the tablets simply disappear into the wash.”

Ariel Stains And Science Schools Programme, PO Box 336 Gateshead, NE11 0XZ.

E-mail: Ariel.science@nbgroup.co.uk