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To determine whether a sample of a substance is pure, you can utilize physical and chemical properties. Here's how:
1. Melting and Boiling Points: Pure substances have well-defined melting and boiling points. By comparing the observed melting and boiling points of a sample with the known values for the pure substance, you can determine if impurities are present. If the observed values deviate significantly from the expected values, it suggests the presence of impurities.
2. Density: The density of a substance is a physical property that can help determine purity. Pure substances have specific densities, and any deviation from the expected value may indicate the presence of impurities. Density can be measured by comparing the mass and volume of the sample.
3. Solubility: The solubility of a substance can also be used to assess its purity. Pure substances often have specific solubility characteristics. By dissolving a sample in a suitable solvent and observing its solubility behavior, such as the rate and extent of dissolution, you can infer the presence of impurities.
4. Spectroscopy: Spectroscopic techniques, such as infrared spectroscopy or nuclear magnetic resonance (NMR), can be used to analyze the molecular structure and identify functional groups present in a sample. Any unexpected peaks or signals in the spectroscopic data may indicate impurities.
5. Chemical Reactions: Pure substances exhibit predictable chemical behavior. By subjecting a sample to known chemical reactions, you can assess its purity. Any unexpected reactions or incomplete transformations may suggest the presence of impurities.
6. Chromatography: Chromatographic techniques, such as thin-layer chromatography (TLC) or high-performance liquid chromatography (HPLC), can separate and analyze the components of a sample. The presence of additional spots or peaks in the chromatogram may indicate impurities.
