Clouds & Particles

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2. Particles

1. What is

a) cloud processing?

b) dry deposition?

c) wet deposition?

2. Aerosols and health

a) Why are small particles more dangerous to inhale than bigger ones?

b) What other property of the particles contributes to determining their health hazardousness?

3. Experiment: Making a cloud in a bottle

You need:

• one transparent plastic bottle (not smaller than 1.5 liter) with a bottle top
• hot water
• matches

Procedure:

1. Be sure that the bottle is clean inside
2. Pour hot water into the bottle till it reaches ca. 3 cm above the bottle bottom.
3. Close the bottle 
4. Rotate the bottle for moistening it inside
5. Pour out the water
6. Light a match. As soon as the tip of the match has finished flaring, blow out the match. 
7. Let a smoke from the match to enter the bottle. (You can for example squeeze the bottle and hold the match close to the opening while you remove the pressure from the bottle. Smoke from the match will then be drawn into the bottle)
8. Close the bottle
9. Increase the pressure inside the bottle by squeezing it. 
   

Can you see a cloud appearing in the bottle? Try to remove the pressure on the bottle, and you will see that the cloud disappears.

Can you explain what happened? Smoke is made up of large numbers of very small particles. Why did you need the smoke for making the cloud in the bottle?

Authors: Ellen K. Henriksen and Camilla Schreiner - University of Oslo - Norway. Scientific reviewer: Justine Gourdeau - LaMP Clermont ferrand - France - 2004-01-13. Last update: 2004-03-27.