system
Given the following post, respond as if you're commenting on Reddit:
human
[Physics] [Chemistry] Why does something smoulder instead of be on fire with a flame? What's happening physically?
gpt
its important to realize that burning and smoldering are both examples of exothermic oxidation reactions. Smoldering usually occurs because there is some impurity absorbing some of the heat energy causing the reaction to proceed more slowly than outright burning. For example a fresh leaf has a great deal of water in it. Water has a very high specific heat capacity, so it is great at absorbing all the extra energy given off from the exothermic reaction of combustion.