Question

during our fuel reactions, what happened to the matter/mass of each fuel sample that was burned? mass was lost mass stayed the same mass was gained mass varied depending on how long each sample burned for

Explanation:

When a fuel burns, it undergoes a chemical reaction. In a chemical reaction, matter is conserved overall (Law of Conservation of Mass). But for the fuel sample itself, as it reacts (burns), it combines with oxygen (in combustion reactions) and forms products like carbon dioxide, water vapor etc. which escape as gases. So the mass of the fuel sample that was burned (the original fuel substance) is lost as it is converted into other substances that leave the system (as gases). It's not that mass is destroyed (as per conservation laws, total mass of reactants = total mass of products in a closed system). But if we are just looking at the fuel sample (not considering the oxygen and products in the measurement of the 'fuel sample' mass), the fuel sample's mass (the part that was burned) is lost.

Answer:

Mass was lost