S3.5.4 For the adult
Diffusion and temperature
Why does a drop of colour spread faster in hot water than in cold water?
What this chapter teaches
The hotter a material is, the faster its particles move on average, so a drop of colour spreads faster in hot water. Cold particles still move, only more slowly. A fair test changes only one thing.
Three questions to ask
There is no one right wording. Listen for the idea.
- Why do you think the colour spreads faster in hot water?
- Do the particles in cold water stand still? What shows it?
- How would you make sure a test of hot and cold water is fair?
After the chapter, the learner can
- Compare how fast colour spreads in hot and in cold water
- Explain why particles spread faster when they are warmer
What they copy into their notebook
The hotter something is, the faster its particles move. Fast particles spread out sooner, so diffusion is quicker when warm. Cold particles still move, only slowly.