What do explosions and roasting marshmallows have in common?
All explosions, regardless of their source, are characterized by a large release of energy, the production of gas molecules that expand quickly, and a rapid rate of reaction.
Burning sugar—chemically known as sucrose (C12H22O11)—produces energy almost immediately. Anyone who has roasted a marshmallow—which is mostly made of sugar—over a fire knows the marshmallow ignites and burns like a torch. This process, called combustion, is described by the following chemical reaction: C12H22O11 (solid) + 12 O2 (gas) ➔ 12 CO2 (gas) + 11 H2O (gas) + energy
Note that there are 12 moles of gas on the left side of the equation for the combustion of sugar but 23 moles of gas on the right side. This explains the increase in volume typical in explosive reactions. What this chemical reaction does not show, though, is that this volume needs to increase rapidly for an explosion to occur.
So, why doesn’t sugar explode or at least light on fire when we eat it? When we eat sugar, sucrose is first digested in the stomach into its component sugars, one of which is glucose (C6H12O6). Glucose subsequently reacts with oxygen in a series of small steps within our cells that produce carbon dioxide (CO2), water (H2O), and energy.
The process can be summarized according to the following equation