Send us your questions

Some of our visitors have sent emails with interesting questions, we decided to start having a space to answer them. In this space the blog "Restless Minds" will answer all questions you send us
Send us your question for the email: Restless Minds.

Science progress affects our daily life and "to know" means you are going to chose right, because it allows you to form your own opinion on scientific everyday issues. On the other hand, having an elegant and harmonious vision of the world where we live in leads to a feeling of intellectual satisfaction.
We believe this kind of scientific day to day knowledge should be encouraged from an early age, and that's why this project was born: science, culture, knowledge, crafts for your restless mind.

Monday, April 1, 2013

1+1 sometimes is not 2

This is one of the greatest math problems, side by side with the one that states that 0 is different than 0. But this demonstration is not about math, is about Archimedes' Principle.

Archimedes' Principle states:
" a body immersed in a fluid is buoyed up by a force equal to the weight of the displaced fluid"

In other words, when we place a body in a fluid, like water, the volume of the object equals the volume of displaced water.

The simplest example is a bath. If we fill the tub with water up to the top and we lay down inside it, the water will exit, and your bathroom will be a very wet place similar to a lake. The amount of water that came out equals your body volume. You can, with some time and work, calibrate the tub to find out your body volume, 1L=1dm3.
In this example 1+1=2, but sometimes 1+1= "not sure" 

What we need :
  • glass container,
  • tape, one you can write on
  • pen,
  • sugar,
  • glass container with a scale,
  • paper towel,
  • straw,
  • spoon,
  • hot water.
How to:
  1. Clean the container;
  2. Apply a vertical strip of tape in the container;
  3. Fill the scaled container with hot water (container A);
  4. Pour the water in the other container (container B); 
  5. Use the pen on the tape to mark the water level in container B;
  6. Fill the container A again and add the water to the container B
  7. Use the pen again and mark the water level in container B;
  8. Reject the water;
  9. With the paper towel clean and dry container B;
  10. Repeat step 3, 4 and 5;
  11. Now fill up the container A with sugar;
  12. Add the sugar to container B;
  13. Use the spoon to mix the solution;
  14. Use the pen to mark the level;
What happens?
1 volume of hot water + 1 volume of sugar it's different from 2 volumes of hot water.

Why?
Water molecules are organized like a net. This net is stable and cohesive due to hydrogen bridges. When this net is formed some hydrogen atoms link to neighbor water molecules by a "false" bond with the oxygen, those are called hydrogen bridges. When this happens some "blank spaces" are left between the molecules- in the net. This spaces are as big as the molecules are excited, thats why we used hot water- more empty space makes dissolution more efficient.

When we add the sugar the sugar molecules occupy the empty spaces between water molecules, thats why:

1 sugar unit+ 1 water unit doesn't equal 2 water units

This is a demonstration, but you can make it an experiment:

Go further:
Try with 1 unit of water+ 1 unit of sugar. Does that equals 2 units of sugar?
Try with cold and ice water, what happens?

Et Voilá!
Now you can teach some stuff to your math teacher

Enjoy!


No comments:

Related Posts Plugin for WordPress, Blogger...