Exothermic reaction energy profile for CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(ℓ) + 890.4 kJ.
Energy diagram showing potential energy vs. reaction coordinate for the combustion of methane, with labeled activation energy (A), energy barrier (B), transition state (C), enthalpy change (D), and final energy level (E).