chap 13 chemical energetics

• Exothermic reactions release heat to their surroundings, while endothermic reactions absorb heat from their surroundings.
• exothermic physical changes examples are dissolving anhydrous salts in water, dissolving of concentrated sulfuric acid in water, condensation, and freezing.
• exothermic chemical changes examples are neutralisation, combustion of fuels, corrosion of metal and respiration.
• in exothermic reactions, heat is released from reactants and transferred to the surroundings. temp of mixture increases and container feels warmer.
• in endothermic reactions, energy is transferred from the surroundings to the reactants. temperature of reaction mixture decreases. container feels cooler.
• physical endothermic changes include dissolving some ionic compounds in water, evaporation, and melting.
• chemical endothermic changes include photosynthesis, thermal decomposition, reaction of dilute acid with sodium hydrogen carbonate, and action of light on silver bromide in photographic film