Which are everyday exothermic reactions?

• A. Photosynthesis
• B. Instant cold packs
• C. Evaporation of water
• D. Hand warmers and burning fuels

Answer: (D)

Exothermic reactions release energy as heat. Everyday examples include hand warmers and burning fuels: hand warmers often work by the oxidation of iron in air, which releases heat as the chemical bonds form and reactants convert to products. Burning fuels like wood, gas, or charcoal also undergo combustion with oxygen, producing heat that warms the surroundings.

The other options involve endothermic processes that absorb heat from the surroundings. Photosynthesis uses light energy to drive reactions, so it absorbs energy. Instant cold packs rely on reactions or dissolutions that take in heat, making them feel cold. Evaporation requires energy to turn liquid water into vapor, which is also an endothermic process.