Answer:
activation energy to start the reaction.
Step-by-step explanation:
The free energy change ΔG of the oxidation of sugar molecules in a sheet of paper in presence of ait has negative value. So the reaction will be spontaneous but it requires initial activation energy which it is not getting at room temperature . So it requires its initial temperature to reach its flash point to attain activation energy . Once it gets activation energy , the further reaction will be automatic due to negative value of ΔG.