Wednesday, April 20, 2011

Float My Egg

The Dead Sea in Jordan is a strange place as the water has an unusually high concentration of salt.  When swimming in the Dead Sea you will float very, very easily. 

To understand why this happens we need to recreate this environment.  So first, we need to build a sea and find some swimmers! 

For this experiment you will need:

  • 2 large glasses
  • Tap water 
  • 2 raw eggs to represent our swimmers
  • Some salt 
Now take an egg and drop it into a glass of water. What happens?

Now slowly add 3 tablespoons of salt and stir gently. What has happened now?

Did your egg sink at first like ours?  After adding the salt the egg should have floated. Why? Because with the salt added, the water be
comes denser.  Now that the water is more dense the egg is pushed upwards and so it floats.
Now for a bit of fun! Half fill the other glass with water and add 10 tablespoons of salt.  Stir well.  Let it settle for a bit and now gentle fill the glass with fresh water.  Don’t stir.  Now add an egg.  The science is the same as above but there a few extra bits going.  See if you can answer these questions.

Why does the egg float half way?
Do you think the salt water and fresh water mix?
Why does this happen?

One of the most interesting factors is that the egg floats because of the changes to the water.  Not because the egg changes.  We also like how it shows that there is more upward lift created by the denser water than by the fresh water.

We hope you enjoyed this Science in Blog.  Check back tomorrow for more eggperiments!