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Activity Number 1 - A Demonstration


To illustrate the difference between visible and invisible air pollution.

Pepper and bowl


  • Clear glass bowl or large clear plastic glasses
  • Tablespoon of milk
  • Teaspoon of pepper
  • Water
  • spoon to stir with

If done as a demonstration, it may help to have a white piece of paper behind the bowl for easier observation.


  1. Fill bowl or cup half full of water.
  2. Add one tablespoon of milk to water, stir.
  3. Add teaspoon of pepper to water, stir.
  4. Observe the differences between the milk and pepper.

Discussion Points

Ask before the experiment:

  • What is the water a model of? (Air)
  • What are the milk and pepper supposed to represent? (Milk is gaseous air pollution, pepper is particulate air pollution)

Ask after the experiment:

  • What kind of pollutants did the the milk act like in the water? (Gases)
  • What kind of pollutants did the pepper act like in the water? (Particulates)
  • What would be easier to get out of the water? (Pepper)
  • Would it be easier to remove gases or particulates out of the air? (In a controlled area, particulates can be removed by filtering the air. To remove gases from the air is more difficult.)
  • How can we measure the gases in the air when we can't see them? (Air samples can be taken for a lab analysis, there are also monitors that can measure some gases like ozone in the air.)
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