Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

You see a faster reaction rate when the concentration of reactants is higher.
What kind of reaction do you see when the concentration of reactants is higher?

Cranium (skull) is the term for the skeletal structure of the head that supports the face and protects the brain.
What is the term for the skeletal structure of the head that supports the face and protects the brain?

Naphthalens is a chemical which is commonly used in mothballs.

Naphthalens is a chemical which is commonly used in what?