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Chemistry notebook Cambridge IGCSE 0620

Diffusion · 2 parts · syllabus 1.2

How does a smell cross a room?

Put a pad soaked in ammonia solution in a long tank of still air and find out which damp litmus strips turn blue first. Then try the pad in the middle, and look at the particles of the gas.

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A long glass tank with its lid held above it; six damp red litmus strips stand along the back and a cotton-wool pad sits near the left end. A bottle of ammonia solution stands beside it. (enlarge)

Follow the idea

  1. A smell you can't see

    Diffusion in gases and liquids, explained with randomly moving particles

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  2. Lighter, faster

    Why lighter gas particles diffuse faster (Supplement)

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The experiment · Ammonia in a closed tank · where is the gas, and which way does it go?

Run it yourself, or project it for the class

Use the apparatus step by step and look closely at what happens. The whole experiment fits one screen, so it works on a projector too.

Open the experiment