Determine whether each process is exothermic or endothermic and indicate the sign of ΔH. a. natural gas burning on a stove b. isopropyl alcohol evaporating from skin c. water condensing from steam Determine whether each of the following is exothermic or endothermic.

Verified step by step guidance

1. Identify the nature of each process in terms of heat flow. Exothermic processes release heat to the surroundings, making the surroundings warmer, and have a negative ΔH. Endothermic processes absorb heat from the surroundings, making the surroundings cooler, and have a positive ΔH.
2. Analyze the process of natural gas burning on a stove. This process involves combustion, which typically releases heat as the chemical bonds in the natural gas break and new bonds form, releasing energy.
3. Consider the process of isopropyl alcohol evaporating from skin. Evaporation generally requires heat to be absorbed from the surroundings (in this case, the skin) to overcome the intermolecular forces in the liquid, indicating an endothermic process.
4. Evaluate the process of water condensing from steam. Condensation involves the transformation of gas to liquid, which usually releases heat to the surroundings as intermolecular attractions are formed, suggesting an exothermic process.
5. Summarize the findings: For natural gas burning, it is exothermic with a negative ΔH. For isopropyl alcohol evaporating, it is endothermic with a positive ΔH. For water condensing, it is exothermic with a negative ΔH.

Key Concepts

Exothermic and Endothermic Processes

Exothermic processes release energy, usually in the form of heat, to the surroundings, resulting in a negative change in enthalpy (ΔH < 0). In contrast, endothermic processes absorb energy from the surroundings, leading to a positive change in enthalpy (ΔH > 0). Understanding these definitions is crucial for classifying chemical reactions and physical changes.

Enthalpy (ΔH)

Enthalpy (ΔH) is a thermodynamic quantity that represents the total heat content of a system. It is used to quantify the energy changes during chemical reactions and phase changes. The sign of ΔH indicates whether a process is exothermic or endothermic, providing insight into the energy dynamics of the reaction.

Phase Changes

Phase changes, such as evaporation and condensation, involve the transition of substances between solid, liquid, and gas states. These changes can be either exothermic or endothermic; for example, condensation releases heat (exothermic), while evaporation requires heat input (endothermic). Recognizing these processes helps in determining the energy changes associated with them.