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Tuesday, January 3, 2012

Gummy Bear Osmosis Demonstration

We already saw Osmosis here "Osmosis demonstration using eggs".

For those who do not remember:

Osmosis is the movement of solvent molecules through a membrane from a region of  lower solute  concentration, to a region of higher concentration.
In other words, and considering the solvent is water, osmosis is the movement of water molecules from "in" or "out" the cell, aiming to match the concentration on both sides of the membrane.


Today we are going to use gummy bears to see this "in" and "out" movement.

What we need:
  • water
  • flask with lid
  • gummy bears
How to:
  1. Wash the flask;
  2. Fill it 1/2 with water;
  3. Take a gummy bear, measure it;
  4. If you have a nice scale try to weigh it;
  5. Place the Gummy bear in the flask;
  6. Close the flask
  7. Wait 24h;
  8. Remove the gummy bear, with careful
What happened?
The bear looks swollen

Why?
A gummy bear is essentially made of gelatin and sugar. We can read on the package

Glucose syrup, sugar, sugar sources;
Water, medium that allows gelatin to form;
Citric acid, helps to conservation;
Flavoring and coloring agents are responsible for the flavor and color;
Covering agents, allow the gelatin to maintain the form and texture;

So, jelly gums are most gelatin water and sugar, molded in a certain shape maintained by the covering agents.
As we seen here, water will travel from a less concentrated solute medium (in this case sugar) to a higher concentrated sugar solution medium. In other words the water will travel from exterior to the gelatin, why? Because the sugar contained in the gummy bear makes it a high concentration medium and the water gets "in" until the concentration is even in both mediums, the gummy bear swells, but it doesn't lose the shape due to the covering agents.

Before remove the gummy bear try:  
To observe the water against the light, to smell and to taste it.
Looks turbid, smells sweet and tastes like gummy bears.
Why?
Because although acting as a membrane, the gummy bear gelatin barrier is not a true membrane, and because the gummy bear is mostly made of water and sugar, some of this sugar ends up free in water, with some of the flavor coloring agents.
 
If you leave the bears a few days in water, the gummy bear stops to swell because reaches itsmaximum capacity point.
At this point we can observe a whitish substance, we couldn't found any information about this, but we believe this is the result of  exposuring the covering agents to water. The fact is when we tried to remove the gummy bear from water the gummy lost its form.

You can transform this demonstration in a experiment:
  • Use different gelatin gums;
  • Weigh and measure the gum before place it in water.
  • After the 24 hours, what changes can you observe?
  • Vary the time of the "bath". The gum reaches a point where it doesn't change the volume? When?
  • Change the liquid "bath", using other substances such as honey, vinegar, sugar water ...
  • ...
Remember:
  • Always write down your observations.
  • Don't change two elements (variables) at the same time.
  • Do not stop to do a test because you think you know what will happen ... DO IT!
Et voil√°!
Gummy bear science!

Enjoy!

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