When this main ingredient arrives from the factory where it is made it comes as large lumps. To make the sun cream, however, this needs to be a powder, like this photograph shows.
Why do you think it needs to be a powder? Any ideas? Could you compare mixing different solid materials and see if you can find the difference?
Activity: To try and answer this question, you could do Activity 7
After that, you can see what our scientists think about this problem