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

Example Input: The combustion of propane gas produces carbon dioxide and water vapor.
Example Output: The combustion of propane gas produces carbon dioxide and what else?

Example Input: The name for a matter that has a fixed volume and a fixed shape is solid.
Example Output: What is the name for a matter that has a fixed volume and a fixed shape?

Example Input: A negative enthalpy change is observed in an exothermic reaction.
Example Output:
What enthalpy change is observed in an exothermic reaction?