In Chemistry, chemical reactions involve the breaking and making of bonds. Depending on whether heat energy is released or absorbed during this process, reactions are classified as Exothermic or Endothermic.
Exothermic: Releases heat (Exo = Exit). Surroundings get hot.
Endothermic: Absorbs heat (Endo = Enter). Surroundings get cold.
Combustion: Always Exothermic.
Decomposition: Usually Endothermic (requires heat to break bonds).
| Feature | Exothermic | Endothermic |
|---|---|---|
| Heat Energy | Released | Absorbed |
| Surroundings | Feel Hotter | Feel Cooler |
| Energy Level | Reactants have more energy than Products | Products have more energy than Reactants |
| Sign of ΔH | Negative (-) | Positive (+) |
Exothermic reactions release heat energy into the surroundings, making them hotter (e.g., burning coal). Endothermic reactions absorb heat energy from the surroundings, making them cooler (e.g., melting ice).
Respiration is an exothermic reaction because it breaks down glucose in our cells to release energy that our body uses.
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