π What are Endothermic Reactions?
Endothermic reactions are chemical reactions that absorb heat from their surroundings. Think of it like the reaction is 'taking in' energy in the form of heat.
π₯ What are Exothermic Reactions?
Exothermic reactions, on the other hand, release heat into their surroundings. In this case, the reaction is 'giving off' energy as heat.
π¬ Endothermic vs. Exothermic Reactions: A Side-by-Side Comparison
| Feature |
Endothermic Reaction |
Exothermic Reaction |
| Heat |
Absorbed |
Released |
| Energy Change |
Positive ($\Delta H > 0$) |
Negative ($\Delta H < 0$) |
| Temperature of Surroundings |
Decreases |
Increases |
| Examples |
Melting ice, Photosynthesis |
Combustion, Neutralization |
| Feel |
Cold to the touch |
Warm to the touch |
| Bond Energy of Reactants vs Products |
Products have higher bond energy |
Reactants have higher bond energy |
| Activation Energy |
Generally higher |
Generally lower |
π§ͺ Key Takeaways
- π‘οΈ Endothermic reactions absorb heat, making the surroundings cooler.
- π₯ Exothermic reactions release heat, making the surroundings warmer.
- π± Photosynthesis ($6CO_2 + 6H_2O + \text{light} \rightarrow C_6H_{12}O_6 + 6O_2$) is a classic endothermic example.
- π₯ Combustion (e.g., burning wood: $C + O_2 \rightarrow CO_2$) is a classic exothermic example.
- π The sign of $\Delta H$ tells you whether a reaction is endothermic (positive) or exothermic (negative).