Question 4
In activity 3.1.3 the clay water was clearer at the top than at the bottom after an hour. Why?
The right answer is the one marked above.
The clay particles are spread unevenly through the liquid. They are large enough to settle, so more of them end up low down and fewer stay near the surface.
Had the clay dissolved, the mixture would have been a solution and uniform from top to bottom — which is exactly what the salt did in the next activity.