CHEM 001 Class 4 Class Notes January 23, 2008 C. Cecil Cuppett, Ph.D. Chapter 2: 1. A physical property of a substance involves only the substance itself. In a physical property change, no chemical change occurs. Pure water remains water whether it is solid, liquid, or gas. Density, melting point, color, and hardness are some physical properties. 2. Physical changes may occur such as freezing (melting), boiling (condensation), or sublimation (deposition). 3. Chemical change is the changing of one substance into another substance. (Burning paper, rusting iron) 4. Dissolving a substance implies a second substance (solvent) is necessary to help with the dissolution. 5. Melting implies just one pure substance becomes hot enough to turn from a solid into a liquid. 6. Evaporation is the process of a molecule escaping the liquid phase and going to a gas phase. Our noses are good vapor detectors. Liquids that evaporate easily are said to be volatile and create a high vapor pressure . (gasoline, perfume, acetone, and turpentine)
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