Evaporation of water is:
Correct answer: A. An endothermic reaction.
- A. An endothermic reaction.
- B. An exothermic reaction.
- C. A process in which no heat changes occur.
- D. A process accompanied by a chemical reaction.
Explanation
Evaporation of water is an endothermic process because it requires energy to overcome the hydrogen bonds between water molecules. This energy is absorbed from the surroundings, leading to a cooling effect. In contrast, an exothermic reaction releases energy, which is not the case here. The process is not without heat changes, as energy absorption is integral to the state change from liquid to gas. Furthermore, evaporation is a physical process, not a chemical reaction, as it involves changing the state of matter without altering the chemical identity of the substance.
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About Thermochemistry and Energetics of Chemical Reactions
Thermochemistry measures energy changes in chemical reactions and distinguishes exothermic from endothermic processes. Work covers systems, surroundings and state functions, internal energy, the first law of thermodynamics, enthalpy and Hess's law, including the sign conventions used when heat enters or leaves a system.
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