How does grind size affect the “permeability” of the coffee grounds?

Question

BlackTom AI · Accepted Answer

When considering how grind size affects the permeability of coffee grounds, it helps to recall what permeability means: the ease with which a fluid can move through a porous medium.
Option 1: 'None of these – the grind size does not affect permeability' This suggests permeability is independent of pore size, which contradicts the basic idea that larger pores allow fluids to pass more easily. In coffee grinding, changing grind size alters the pore network, so this statement is unlikely to be correct.
Option 2: 'Bigger coffee grounds have bigger permeability (it is easier to push the fluid through)' This aligns with the principle that larger particles create larger interstitial spaces and channels, increasing pore size and reducing flow resistance, so fluid would flow more readily.
Option 3: 'Bigger coffee grounds have smaller permeability (it is harder to push the fluid through)' This directly contradicts the pore-structure reasoning: increasing particle size typically enlarges pore spaces, not reduces them, so this option is inconsistent with fluid flow through porous media.
Option 4: 'Bigger coffee grounds increase the viscosity of the fluid (so the permeability must decrease)' In general, the grind size affects the pore structure more than the intrinsic viscosity of the liquid; while blending changes with extraction can alter apparent viscosity, the core permeability is governed by pore geometry rather than a direct increase in the liquid's viscosity due to grind size. This option introduces an incorrect causal link.
Taken together, the reasoning supports that larger grind sizes create larger pores and pathways, which reduces resistance and increases permeability, making fluid flow easier. The other options either deny the relationship, assert the opposite, or rely on an incorrect mechanism involving viscosity.

How does grind size affect the “permeability” of the coffee grounds?单项选择题

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