December 16, 2017

Water Magic And The Mpemba Effect

Here at Ghscientific we are very interested in the wonders of everyday science around us. So after looking at what makes hair luscious, attention has now been turned to one of the most common things we have around us; water. Water covers over 70% of the Earth’s surface, forms 60% of your body mass and someone managed to propagate the idea that we must drink about 3 litres of water daily (for you and me that is equal to 6 pure water sachets).  Despite being around even before God said “Let there be light” and being so vital to life, there is so much about water we still don’t know.

  • Water does not behave like other liquids

If all liquids were students in a class, water will be that kuborlor (truant) who never turns up or obeys the rules. If whiles in school you were never a kuborlor yourself then you will know that gases take up more space than liquids and liquids take up more space than solids.

solid liquid gases
Basically when liquids freeze, they take up less space as the molecules are slowed down and caused to pack themselves tighter together. This applies to all liquids, except water which decides to expand when it freezes.  This is why bottles of water crack or break when you leave them in the freezer. On a larger scale this is why ice floats because unlike any other substance, the frozen version is lighter and less dense than the liquid version.

  • Hot water freezes faster than cool water

This is probably hard to get your head round, after all if you have ever tried to make ice cubes in your freezer for an emergency cocktail party you will know it takes a looooong time. Now imagine trying this with hot water, understandably it should take even longer right? Well not exactly and to help you out, below is a video showing just how quickly hot water can freeze.

[youtube=http://www.youtube.com/watch?v=QCrrJs2areo]

See under the right conditions, hot water can freeze faster than cool water. This phenomenon has been known for a long time but in 1969 a high school student in Tanzania named Erasto Mpemba described and defined it, so now it is named after said student; the Mpemba effect. No one knows exactly what causes the Mpemba effect but there are a couple of factors that definitely contribute; like starting temperature, humidity, water purity and even the shape of the container.

  • Why is ice slippery?

You are probably thinking asking that question is like asking why is water wet?. Agreed, we intuitively expect ice to be slippery but the thing is scientifically speaking there is no particular reason why it should be. There is definitely less friction but the question is why? See even when the surface looks rough, ice is slippery and no matter how you much you polish or smooth over a piece of furniture it will never be slippery as ice. True to its nature, science has theories. Ranging from sound arguments such as the surface of water still been liquid because of the air pressure to outlandish arguments such as ice is not slippery at all, it’s all in our head!

  • Water is a dangerous explosive

So far you have been presented with some outlandish concepts but thankfully here is one you can try at home. All you need is the following:

  1. Pure water. And I don’t mean Voltic or Bel-Aqua but distilled water which is as pure as water can get.
  2. A microwave
  3. A coin
  4. A signed agreement to absolve Ghscientific of any injuries or damages during the performance of this experiment

Understandably number 1 and 4 may be a bit tricky to come by so here’s a video showing you this magic in action:

[youtube=http://www.youtube.com/watch?v=SC_NtH8vWSc]

Now on this, science has a bit more information but it doesn’t take away from how awesome it is. If you heat distilled water without any impurities then the water never boils although it gets hot. So the second you introduce an impurity or a point of disturbance……..BOOM, all the boiling happens in an instant.