Fig 7A reaction rearranges atomsmethane burningsame atoms both sides
When methane burns, its bonds and oxygen's bonds break and the atoms join up again as carbon dioxide and water. No atom is made or destroyed, so both sides hold one carbon, four hydrogens and four oxygens, and the numbers in front of each molecule are chosen to make that true. The energy comes from the bonds: the new ones are stronger than the old ones, and the difference is released as heat.