Video Transcript
A student must separate a sample of sand from a water suspension. Which technique should the student use? (A) Filtration, (B) distillation, (C) evaporation, (D) crystallization, or (E) centrifugation.
As it turns out, all of the answer choices listed are a type of separation technique, each with their own process and application. Let’s use this table to highlight each of their specific uses in order to determine which is the correct answer. Filtration is a separation technique that can be used to separate an insoluble solid from a liquid. This can be accomplished through gravity filtration, which is typically used for large mixture samples and/or when the mixture needs to be separated while hot, or vacuum filtration, which is typically used for small mixture samples.
Distillation is a separation technique that can be used to separate two miscible liquids that have different boiling points, with miscible substances defined as substances that fully dissolve in one another to form a homogeneous solution. Evaporation and crystallization are separation techniques that can be used to separate a dissolved solid from a liquid. While their general uses are similar, the main differences are that evaporation is used when the solution contains only one soluble solute, there are no known impurities, and large crystals are not needed.
Crystallization is used when the solution is known to contain two or more known soluble solutes that have different solubilities, the solution contains impurities, and/or large crystals are needed. And finally, centrifugation is a separation technique commonly used to separate very fine suspended particles or extremely small solids from a liquid.
Now let’s analyze the mixture we need to separate to determine which separation technique would work best. In regards to the sand and water mixture mentioned, a key point to highlight is that sand is an insoluble solid mixed in water, meaning it does not dissolve in the water. This eliminates distillation, evaporation, and crystallization as a viable technique to separate sand from water because each of these techniques requires all substances involved to be soluble or dissolved in one another. In addition, the sand particles are quite large, so centrifugation will not be the best method for separation because it is based on the separation of fine or small particles from a liquid.
Therefore, the technique that the student should use to separate a sample of sand from water is filtration. This is because with the sand particles being quite large and insoluble in water, they will not pass through the filter paper. Water, on the other hand, will pass through the filter paper and in turn will be separated from the sand. Which technique should a student use to separate sand from water? The answer is option (A) filtration.
