Answer: Melting point determination can be used to distinguish between a pure sample and an impure sample because the presence of impurities will usually lower the melting point of a substance.
Step-by-step explanation:
When a pure substance is heated, it will begin to melt at a specific temperature known as its melting point. However, when an impure substance is heated, the presence of impurities will cause the melting point to decrease and the substance to melt over a range of temperatures.
Therefore, by comparing the melting point of a sample to the known melting point of a pure substance, we can determine whether the sample is pure or impure. If the sample has the same melting point as the pure substance, then it is likely pure. However, if the sample melts over a range of temperatures or at a lower temperature than the pure substance, then it likely contains impurities.