The purpose of this lab is to determine the percentage of sand, silt, and clay in soil samples using a hydrometer that measures the density of a solution.
The hydrometer method is based on Stokes’ Law. Stokes’ Law states denser particles (usually larger) sink faster than less dense particles (smaller) when suspended in liquid (of a given temperature). There are two critical assumptions regarding this: 1) the particles all have the same density--thus larger ones will settle first, and 2) the particles are spherical. Actually, neither of these can be perfectly satisfied.
The hydrometer thus measures the density of the soil/water mixture. The more particles that are in suspension, the more dense the soil/water mixture will be. The more dense the mixture, the better it will support an object placed in the mixture. That is, the more dense the mixture, the higher the hydrometer will float in the soil/water mixture. As larger particles fall from suspension, the density of the soil/water mixture decreases. As the density decreases, the hydrometer sinks farther into the mixture. The stem of the hydrometer is marked in grams of sediment remaining in suspension.
You will be analyzing two soils.
The purpose of this lab is to determine the percentage of sand, silt, and clay in soil samples using a hydrometer that measures the density of a solution.The hydrometer method is based on Stokes’ Law. Stokes’ Law states denser particles (usually larger) sink faster than less dense particles (smaller) when suspended in liquid (of a given temperature). There are two critical assumptions regarding this: 1) the particles all have the same density--thus larger ones will settle first, and 2) the particles are spherical. Actually, neither of these can be perfectly satisfied.The hydrometer thus measures the density of the soil/water mixture. The more particles that are in suspension, the more dense the soil/water mixture will be. The more dense the mixture, the better it will support an object placed in the mixture. That is, the more dense the mixture, the higher the hydrometer will float in the soil/water mixture. As larger particles fall from suspension, the density of the soil/water mixture decreases. As the density decreases, the hydrometer sinks farther into the mixture. The stem of the hydrometer is marked in grams of sediment remaining in suspension.You will be analyzing two soils.
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