Answer:
by determining how much heat and light are produced in the reaction
Step-by-step explanation:
The amount of energy that is given off when a fuel burns depends on the type of fuel and how it reacts with oxygen. Fuels are made of different kinds of atoms and molecules, which have different amounts of energy stored in their bonds. When a fuel burns, it breaks these bonds and forms new ones with oxygen, releasing some of the energy as heat and light. Some fuels have more energy per unit mass than others, because they have more hydrogen atoms or more complex molecules in their structure. Hydrogen atoms have more energy than carbon atoms, and complex molecules have more energy than simple molecules, because they have more bonds to break and form during combustion.