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Investigation 2 - Water

The Mpemba Effect

Some scientists have discovered that water doesn’t always freeze how you would expect. Erasto Bartholomeo Mpemba was a young student of 11 or 12 years of age at school in Tanzania when he observed a phenomenon which today carries his name, all because he was in a rush to freeze hot cream. Mpemba noticed that the warm cream froze faster than he expected. He wondered if all warm liquids freeze faster than cold ones and went on to test this.


Scientists at the University of Southampton are investigating the Mpemba Effect, to see if this discovery could be more widely applicable. To do so, they need lots of people to repeat the same scientific investigation. That is where we come in. We carried out the investigation that Mpemba did to see if warm water freezes quicker than cool water.


The University of Southampton would also like some extra information on water hardness and to see if this has an effect on how water freezes.


To do this we used water testing strips. These change colour when you dip them into tap water. The colour indicates whether our tap water has lots of dissolved minerals; what we consider to be hard water, or few dissolved minerals: we call this soft water.