Final answer:
Willa is studying a colloid, which is a type of mixture where the particles are dispersed and do not settle but are large enough to scatter light.
Step-by-step explanation:
Based on the given information, Willa is studying a colloid.
A colloid is a type of mixture where the particles are larger than those in a solution but smaller than those in a suspension. In a colloid, the particles are dispersed and do not settle, but they are large enough to scatter light. This is why the light was scattered when Willa passed a concentrated beam of light through the mixture.
Examples of colloids include milk, fog, and clouds.