Question

Recall that the random movement of molecules tends to drive them down their concentration gradient, producing greater disorder, until equilibrium is reached as the materials become evenly distributed. Organisms rely on this diffusion for the distribution of water, gases, and some solutes across selectively permeable cell membranes. The rate of diffusion is the amount of substance moving per unit time, and it is commonly expressed in units such as millimoles per second (mmol/s). According to Fick's law, the rate of diffusion of a particular substance is proportional to the diffusion constant (k), which depends on the physical and chemical properties of the diffusive particle (the substance in question) and the medium in which it is diffusing. In general, k is higher for smaller particles and lower for a high viscosity medium. As you would expect, diffusion is greater over a larger surface area than over a smaller area (more of the substance will pass through a larger area than through a smaller area). The driving force responsible for the net diffusion of the substance is the concentration gradient (C/D), as summarized in the equation below. Rate of diffusion = Diffusion constant (k) % Area % concentration difference (C) / distance of diffusion path (D) a. Would you expect k to be higher for water compared to the k for diffusion in air, and why?

          Recall that the random movement of molecules tends to drive them down their concentration gradient, producing greater disorder, until equilibrium is reached as the materials become evenly distributed. Organisms rely on this diffusion for the distribution of water, gases, and some solutes across selectively permeable cell membranes. The rate of diffusion is the amount of substance moving per unit time, and it is commonly expressed in units such as millimoles per second (mmol/s).
According to Fick's law, the rate of diffusion of a particular substance is proportional to the diffusion constant (k), which depends on the physical and chemical properties of the diffusive particle (the substance in question) and the medium in which it is diffusing. In general, k is higher for smaller particles and lower for a high viscosity medium. As you would expect, diffusion is greater over a larger surface area than over a smaller area (more of the substance will pass through a larger area than through a smaller area). The driving force responsible for the net diffusion of the substance is the concentration gradient (C/D), as summarized in the equation below.
Rate of diffusion = Diffusion constant (k) % Area % concentration difference (C) / distance of diffusion path (D)
a. Would you expect k to be higher for water compared to the k for diffusion in air, and why?

Recall that the random movement of molecules tends to drive them down their concentration gradient, producing greater disorder, until equilibrium is reached as the materials become evenly distributed. Organisms rely on this diffusion for the distribution of water, gases, and some solutes across selectively permeable cell membranes. The rate of diffusion is the amount of substance moving per unit time, and it is commonly expressed in units such as millimoles per second (mmol/s).
According to Fick's law, the rate of diffusion of a particular substance is proportional to the diffusion constant (k), which depends on the physical and chemical properties of the diffusive particle (the substance in question) and the medium in which it is diffusing. In general, k is higher for smaller particles and lower for a high viscosity medium. As you would expect, diffusion is greater over a larger surface area than over a smaller area (more of the substance will pass through a larger area than through a smaller area). The driving force responsible for the net diffusion of the substance is the concentration gradient (C/D), as summarized in the equation below.
Rate of diffusion = Diffusion constant (k) % Area % concentration difference (C) / distance of diffusion path (D)
a. Would you expect k to be higher for water compared to the k for diffusion in air, and why?

Added by Celia M.

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