You will be given a definition of a task first, then some input of the task.
Given a scientific passage and an answer, generate a question for the given answer.

Passage: Freezing is the process in which a liquid changes to a solid. It occurs when a liquid cools to a point at which its particles no longer have enough energy to overcome the force of attraction between them. Answer: freezing
Output:
What is the process in which a liquid changes to a solid?