Given a scientific question and its correct answer, generate supporting facts for the answer. This supporting fact can be an explanation for the answer to the given question.

Example Input: Question: What happens to water when it is heated in the broiler? Answer: it expands
Example Output: When water is heated in the boiler, it expands. It might burst the pipes of the system if it weren't for the expansion tank. This tank holds excess water after it expands.

Example Input: Question: What changes the chemical composition of a substance and can only occur through a chemical reaction? Answer: chemical changes
Example Output: Pure substances, such as compounds, can be separated through chemical changes. Chemical changes change the chemical composition of a substance and can only occur through a chemical reaction.

Example Input: Question: What is the unit of evolution? Answer: the population
Example Output:
The population is the unit of evolution.