Separation of Sand and Salt
Start this lab well in advance of the due date. It may take several days to evaporate all the water
Background
In this experiment you will observe a material and classify it as a pure substance, a homogeneous mixture, or a heterogeneous mixture. You will then perform a series of experiments on this material and classify the components as a pure substance, a homogeneous mixture, or a heterogeneous mixture while analyzing the unknown quantitatively.
The Correct Answer and Explanation is:
Correct Answer:
The mixture of sand and salt is a heterogeneous mixture. Sand is a pure substance (specifically, silicon dioxide), and salt (sodium chloride) is also a pure substance. When salt is dissolved in water, it forms a homogeneous mixture (a salt solution). When the salt solution is separated from the sand, we separate the components based on their physical properties: solubility and filtration.
Explanation:
In this lab, the initial material—sand mixed with salt—is a heterogeneous mixture. This classification is based on the fact that the two components, sand and salt, retain their individual properties and can be physically distinguished from one another. The particles of sand and salt do not mix uniformly; you can see and separate them without altering their chemical identities.
To separate this mixture, water is added. Salt is soluble in water, whereas sand is not. When water is added, only the salt dissolves, creating a homogeneous mixture (a saltwater solution), while the sand remains as a solid. This demonstrates how solubility can be used as a physical property for separation.
The next step involves filtration, where the sand is separated from the saltwater solution using filter paper. The sand stays on the filter paper as a residue, confirming it as a pure substance (not dissolved and unchanged). The saltwater passes through as the filtrate, a homogeneous mixture.
To separate the salt from the saltwater, evaporation is used. By heating or allowing the water to evaporate over several days, the water is removed, leaving behind salt crystals. Since salt is recovered in its original form, it is also a pure substance.
This experiment demonstrates physical separation methods—filtration and evaporation—and illustrates how mixtures can be broken down into their pure components using physical properties. It reinforces the concepts of mixture types and the classification of matter, which are essential for understanding more complex chemical systems.
