Determining the purity of a sample using melting point determination involves comparing the melting point of the unknown substance to the known melting point of a pure reference substance. The principle behind this method is that impurities in a substance usually lower its melting point and broaden the melting point range. A pure substance typically has a sharp, well-defined melting point.Here are the steps to determine the purity of a sample using melting point determination:1. Obtain a reference substance: Find a reference substance with a known melting point that is expected to be similar to the unknown substance. This can be done by referring to a chemical database or literature.2. Prepare the samples: Crush the unknown substance and the reference substance into fine powders. Mix a small amount of the unknown substance with an equal amount of the reference substance to create a mixture.3. Load the samples into capillary tubes: Load a small amount of the unknown substance, the reference substance, and the mixture into separate capillary tubes. Seal one end of each capillary tube and tap the sealed end on a hard surface to pack the samples tightly.4. Determine the melting points: Place the capillary tubes in a melting point apparatus, which gradually heats the samples and allows you to observe the melting process. Record the temperature at which each sample starts to melt onset of melting and the temperature at which the sample has completely melted.5. Compare the results: Compare the melting point range of the unknown substance to the known melting point of the reference substance. If the unknown substance has a sharp melting point that matches the reference substance, it is likely pure. If the melting point of the unknown substance is lower and has a broader range, it is likely impure. The mixture of the two substances should have a lower melting point and a broader range than the pure reference substance, which further confirms the presence of impurities in the unknown sample.Keep in mind that melting point determination is a preliminary test for purity and may not provide conclusive results for all substances. Other techniques, such as chromatography or spectroscopy, may be necessary for a more accurate assessment of purity.