Q: Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
Gases were released to the atmosphere best explains why the total mass of the product(s) would be less than the total weight of the reactant(s) after a chemical reaction.
A:
Which best explains why the total mass of the product(s) would be less than the total weight of the reactant(s) after a chemical reaction?