Question

which represents an endothermic reaction?
wood burning in a fire
splitting a gas molecule
using a heat pack on an injury
tnt exploding

Explanation:

• Wood burning in a fire: Combustion is an exothermic reaction as it releases heat.
• Splitting a gas molecule: Breaking bonds requires energy input. This is characteristic of an endothermic reaction.
• Using a heat - pack on an injury: Heat packs usually work via exothermic chemical reactions (e.g., oxidation of iron in some types) to release heat.
• TNT exploding: Explosions are highly exothermic as they release a large amount of energy rapidly.

Answer:

splitting a gas molecule