Several processes are given in the table and labeled as endo- thermic or exothermic and given a sign for ∆H°. Which process is labeled with the correct sign of ∆H° and correct classification as endothermic or exothermic? (LO 9.8) Process (d) Rubbing alcohol evaporates from your skin.

Verified step by step guidance

1. Identify the type of process: Evaporation is a phase change from liquid to gas.
2. Understand the energy requirement: Evaporation requires energy to overcome intermolecular forces, making it an endothermic process.
3. Determine the sign of \( \Delta H^\circ \): For endothermic processes, \( \Delta H^\circ \) is positive because energy is absorbed.
4. Relate the process to the classification: Since rubbing alcohol evaporating is endothermic, it should have a positive \( \Delta H^\circ \).
5. Verify the classification: Ensure that the process is correctly labeled as endothermic with a positive \( \Delta H^\circ \).

Key Concepts

Endothermic and Exothermic Processes

Endothermic processes absorb heat from their surroundings, resulting in a decrease in temperature of the environment, while exothermic processes release heat, increasing the temperature of the surroundings. The classification of a process as endothermic or exothermic is determined by the sign of the enthalpy change (∆H°); a positive ∆H° indicates an endothermic reaction, and a negative ∆H° indicates an exothermic reaction.

Enthalpy Change (∆H°)

Enthalpy change (∆H°) is a measure of the heat content of a system at constant pressure. It quantifies the energy absorbed or released during a chemical reaction or physical process. In the context of phase changes, such as evaporation, the enthalpy change reflects the energy required to overcome intermolecular forces, which is crucial for understanding whether a process is endothermic or exothermic.

Evaporation and Heat Transfer

Evaporation is a physical process where liquid molecules gain enough energy to transition into the gas phase. This process is endothermic because it requires heat energy to break the intermolecular forces holding the liquid molecules together. When rubbing alcohol evaporates from the skin, it absorbs heat from the skin, leading to a cooling sensation, which is indicative of an endothermic process.