Brownian motion and diffusion
Answers are for parents and teachers.
1
At home (with an adult) put a drop of food colouring into two glasses, one with cold and one with warm water, and write in which the colour spreads faster.
It spreads faster in warm water because the molecules move faster.
2
The dye rose 12 mm in 6 hours. What is the diffusion rate h : t in mm/hour?
2
3
Give three examples of diffusion you meet at home.
The smell of food spreading, sugar dissolving in tea, the smell of perfume.
4
Why are two wet smooth plates hard to separate? Write 2–3 sentences.
The water layer brings the molecules of the plates close together and attractive forces act between them.
5
Describe diffusion in solids briefly and give one example.
It is very slow; for example, gold and lead plates penetrated each other by about 1 mm in several years.