S3.1.7 For the adult
Diffusion
Why can you smell cooking from across a room?
What this chapter teaches
Particles spread by their own movement from a crowded place to a less crowded one. This is diffusion. It is faster in a gas than in a liquid, and slow in still water. Cells take in oxygen and lose carbon dioxide by diffusion.
Three questions to ask
There is no one right wording. Listen for the idea.
- Why can you smell dinner cooking in another room?
- Which way do particles spread in diffusion, and why?
- How would you show diffusion with ink and a glass of water?
After the chapter, the learner can
- Explain diffusion as spreading from a crowded place to a less crowded one
- Show diffusion with a drop of ink or tea in still water
What they copy into their notebook
Diffusion is the spreading of particles from where they are crowded to where they are less crowded. It needs no stirring. In still water it is slow. Cells take in oxygen by diffusion.