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Monday, December 12, 2011

Floating grape- density matters

This is another demonstration of density, your restless will love this floating grapes.

Density is what does float in the air, ice cubes float on drinks and stones "drop dead" in the bottom of the lake.
We are going to make a grape to float on a glass with water.

What we need:

  • 3 transparent cups,
  • tape,
  • pen,
  • measuring cup,
  • water,
  • sugar,
  • 3 grapes,
  • tablespoon,
  • paper sheet.
How to:
  1. With the pen, the paper and the tape, make 3 labels for the 3 cups- Cup1 Cup2 Cup3;
  2. Fill the measuring cup with water;
  3. Add sugar until the solution is saturated, it will be saturated when some of the sugar, not many, remains on bottom, even after you mix it well with the spoon;
  4. Fill the Cup1 with tap water;
  5. Place a grape inside, what happens?;
  6. Fill the Cup2 with the sugar solution;
  7. Place another grape on the cup, what happens?;
  8. Now, fill 1/2 of the Cup3 with the sugar solution;
  9. With careful fill the rest of the Cup3 with tap water. The best way to do this is to use a spoon. Place it inside the cup, without touching the sugar solution, let the water drain along the spoon, as we saw here.
  10. Place a grape inside the cup. What happens now?

The grape is denser then the water, so it sinks.
The sugar solution is denser then grape, so the grape floats. But the sugar water is denser then the tap water, when we place this 2 liquids in layers, the grape its trapped between the layers and floats.

If you prepare the sugar solution several hours before use it, the difference between the 2 are imperceptible, and really looks "a kind of magic";

Make this a experiment, try to use salt or substitute grapes for raisins... What happened? Keep your results in a log.

Et Voilá!
It's a kind of magic...


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