When a bottle of perfume is opened, odorous molecules mix with air and slowly diffuse throughout the entire room. Is ΔG for the diffusion process positive, negative, or zero? What about ΔH and ΔS for the diffusion?

Verified step by step guidance

1. Step 1: Understand the concept of diffusion. Diffusion is the process by which molecules spread from an area of high concentration to an area of low concentration, resulting in a more uniform distribution of molecules.
2. Step 2: Consider the change in Gibbs free energy (ΔG) for the diffusion process. Since diffusion is a spontaneous process, ΔG is negative. Spontaneous processes occur without the input of external energy and result in an increase in entropy.
3. Step 3: Analyze the change in entropy (ΔS) for the diffusion process. As the perfume molecules spread throughout the room, the disorder or randomness of the system increases. Therefore, ΔS is positive.
4. Step 4: Evaluate the change in enthalpy (ΔH) for the diffusion process. Diffusion is typically an isothermal process, meaning it occurs at constant temperature without a significant change in heat content. Thus, ΔH is approximately zero.
5. Step 5: Summarize the thermodynamic changes: For the diffusion of perfume molecules, ΔG is negative (spontaneous process), ΔS is positive (increase in disorder), and ΔH is approximately zero (isothermal process).

Key Concepts

Gibbs Free Energy (ΔG)

Gibbs Free Energy (ΔG) is a thermodynamic potential that indicates the spontaneity of a process at constant temperature and pressure. A negative ΔG suggests that a process is spontaneous, while a positive ΔG indicates non-spontaneity. In the case of perfume diffusion, the process is spontaneous as the molecules spread out, leading to a negative ΔG.

Enthalpy (ΔH)

Enthalpy (ΔH) is a measure of the total heat content of a system. It reflects the energy required to break intermolecular forces during a process. For diffusion, the enthalpy change is typically small or slightly positive, as the energy required to overcome interactions is minimal compared to the increase in disorder.

Entropy (ΔS)

Entropy (ΔS) is a measure of the disorder or randomness in a system. During diffusion, the odorous molecules move from a region of higher concentration to one of lower concentration, increasing the overall disorder of the system. This results in a positive ΔS, indicating that the diffusion process contributes to greater randomness in the arrangement of molecules.