The difference between exothermic and endothermic reactions lies in energy transfer, specifically whether energy (usually heat) is released or absorbed during the reaction. Here’s a breakdown:
1. Exothermic Reactions
- Definition: A reaction that releases energy to the surroundings, often as heat, light, or sound.
- Energy Change: The energy of the products is lower than that of the reactants. The excess energy is given off.
- Temperature Effect: Surroundings usually get warmer.
- Examples:
- Combustion of fuels (e.g., burning wood or gasoline)
- Respiration (glucose breakdown in cells)
- Condensation of water vapor
- Energy Diagram: Reactants start higher than products; the energy difference is released.
2. Endothermic Reactions
- Definition: A reaction that absorbs energy from the surroundings.
- Energy Change: The energy of the products is higher than that of the reactants because energy must be supplied.
- Temperature Effect: Surroundings usually get cooler.
- Examples:
- Photosynthesis (plants absorb sunlight to make glucose)
- Melting ice
- Evaporation of water
- Energy Diagram: Reactants start lower than products; energy must be absorbed to proceed.
Quick Tip to Remember:
- Exo → Exit energy → releases heat
- Endo → Enter energy → absorbs heat