-
Asked by to Daren, Lynne, Phillip, Simon on 23 Jun 2014. This question was also asked by .
-
anon answered on 23 Jun 2014:
This is called the Mpemba effect and nobody really knows how it works. There was a competition run recently by the Royal Society of Chemistry to try and explain it and this was the winning video:
The effect is named after a school student in Tanzania who asked the question to a scientist who came to do a talk. He’d noticed it happening when freezing mixtures to make ice cream in his food tech lessons. The rest of his class mocked him for his question, but the scientist thought it was really interesting so they researched it together.
-
-
Daren Fearon answered on 23 Jun 2014:
Like Jenny pointed out, this is known as the Mpemba effect and we don’t have a definite answer, yet atleast. This is unique to water though. Water is also unique in that when it is frozen it takes up more space than when it is a liquid (other liquids don’t do this) due to the way the molecules interact and pack together. Maybe this has a role in the Mpemba effect?
-
Lynne Thomas answered on 23 Jun 2014:
Yes water is a very strangely behaving liquid. It also boils at a much higher temperature than such a small molecule should – usually the bigger the molecule, the higher the boiling point. This is because of the hydrogen bonds which hold the molecules together and these are quite strong bonds to break! Its these that also make water expand when it freezes which is really useful for us if we want to go ice skating or skiing – if we put pressure on ice by standing on it, it wants to take up less space and the only way it can do this is by melting so we get a layer of water underneath us which allows us to slide on it!
Its fascinating that a molecule which only has two atoms, an oxygen atom and two hydrogen atoms, can be so difficult to understand! But without it we wouldn’t have life as we know it 🙂
Comments