Energy profile diagram for the combustion of methane, showing exothermic reaction with negative enthalpy change.

A graph showing the energy profile of a combustion reaction, with the x-axis labeled "Progress of reaction" and the y-axis labeled "Energy." The graph illustrates the energy change from reactants (CH₄(g) + 2O₂(g)) to products (CO₂(g) + 2H₂O(l)), highlighting the activation energy, energy absorbed as bonds break, and energy released as bonds form. The enthalpy change (ΔH) is indicated as -890 kJ mol⁻¹.