A tea bag is put in a cup of hot water and another in a cup of cold water.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A tea bag is put in a cup of hot water and another in a cup of cold water. Nobody stirs. In which cup does the colour spread faster? Give a reason.
Need a reminder? The key ideaShow
Diffusion is the net movement of particles from a higher to a lower concentration. It needs no energy, is faster when warmer, and its time grows with the square of the distance.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Which cup. The hot one.
Step 2. Why. In hot water the particles move faster, so the coloured particles spread out faster by diffusion.
Answer: in the hot water, because diffusion is faster when it is warmer.
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