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Understanding diffusion

Background

The key to understanding diffusion, is realizing that diffusion is all about balance! Diffusion happens because there is an imbalance, and will stop when the balance is restored.

Not sure what I am on about? This experiment will help you understand.

Check out Good-Science-Fair-Project.com's definition of diffusion to get a jumpstart to understanding diffusion before you do the experiment.

Let's do science...

The Experiment

So we now know that diffusion is basically all about re-establishing a balance. So how and why does this happen?

The Aim
To demonstrate diffusion of water and so gain a better understanding of how and why it happens.

Equipment Needed

  • Two glasses
  • Water
  • Paper towel or filter paper
  • Food coloring

    Method

  • Fill the one glass with water until it is half to two thirds full.
  • Add some food coloring to this glass's water (this simply makes the water easier to see).
  • Take the paper towel / filter paper and roll it into a long (about 20 cm) tight, roll.
  • Place the one end of the roll of paper towel into the glass of colored water and the other end into the other, empty, glass.
  • Leave it overnight, or as long as is needed.

    Results
    This is what you should see happening...

  • The water will move up the paper towel from the glass containing the colored water.
  • The water will continue to move towards the empty glass until you start seeing water in this glass.
  • The level of water in the first glass (with the food coloring) will go down while the level in the second glass will go up until they are equal.

    The Conclusion
    Understanding diffusion also means you need to understand concentrations. This will also help you explain what happened during the experiment.

    The paper towel has no water in it, so it is said to have a low concentration of water. So the water will move into it as the glass containing the colored water, which has a higher concentration of water relative to the dry paper towel.

    The water from the first glass will have the higher concentration and so will continue moving through the paper towel to the second glass until the concentration of water is the same in both glasses, or until a balance or equilibrium is reached. This will happen once the level of water is the same in both glasses.


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