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Monday, March 12, 2012

Overcome the force of gravity


When we add salt to water we increase its density, which will allow some objects to float.

What we need:
  • 6 glass jars,
  • different objects, like beans, grains, paper clips, eggs, etc.. we used dry beans, dry grain and an olive;
  • salt,
  • dessert spoon,
  • water,
  • pen,
  • labels,
  • your notepad.
How to:
  1. Clean the jars;
  2. Label them with letters or numbers;
  3. Select the objects you want o test,
  4. Write on your notepad which letter goes with each object, one of the jars will be the control, for example A- control; B- olive; C- bean....;
  5. Fill the jars with the same quantity of water, we used 250ml;
  6. Verify if any of your objects floats;
  7. Write down your results;
  8. Take the objects from the jar;
  9. Add 1 dessert spoon of salt to the B jar, 2 to the C, 3 to the D... don't add any salt to the first jar (control);
  10. Mix it well until the salt is all diluted, if you are using jars with lid is easier to close the jar and shake;
  11. Test all the objects, one by one, jar by jar;
  12. Write down your results.
At the end you will have precise notes about the number of spoons you need to add to water in order to float  a certain object.

These were our results:

A- 0 salt
B- 1 salt
C- 2 salt
D- 3 salt- floats: grain
E- 4 salt- floats: red bean; black bean
F- 5 salt- floats: white bean; olive

Attention: you may get different results; those depend on the beans/grain/olive trademark, size and water content.

It's possible to find on internet and some books some references to some restless minds that made heavier objects to float, like marbles, or stones, using larger amounts of salt. We didn't test those objects, in theory, yes it's possible to make it happen, but the amount of salt in the water will be hugely high.
Accept this challenge and try to float denser objects.

What happens?

As you salt the water, this will become denser, in other words, heavier. This density is closely linked to the force that water exerts on the items, if this force is higher then the force that pushes objects down (gravity) the objects are boost up and float.
With this experiment you can also observe water saturation, write down the number of salt spoons you need to saturate the water.

It is possible to do some variations to this essay:
  • Use only one kind of bean but with different water levels (1 dry, hydrated but raw and 1 cooked);
  • Use only one kind of bean with different water levels, from 3 different trademarks (dry, hydrated, cooked from trademark A, dry, hydrated, cooked from trademark B; dry, hydrated, cooked from trademark C);
  • Use green olives or black, with pit, without pit...
Write down your results.

Et voil√°!
Can you make it work with the marble?

Enjoy!

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