Why This Chapter?
What atomic number is to an atom, the physical and chemical properties are to a compound. These properties help to identify and classify a compound, predict its nature, and determine its suitability in chemical reactions.
A physical property measurement involves sensory evaluations or measurements without any changes in the composition of the substance. Physical properties help evaluate a compound for its volatility, determine its flash point, melting point, boiling point, density, appearance, odor, and solubility, and provide ways to tell it apart without the compound undergoing any chemical reaction or bond breaking.
Since, understanding a compound's nature becomes very important in situations that require assistance, like a fire caused by a gas leak or an oil spill. For example, you can't douse a fire caused by sodium metal using water; the intensity would increase tremendously since sodium metal is highly reactive to water. Nor can opening the windows help in high-density gas leaks since the gas would be primarily concentrated near the floor.
Organic reactions happen when the reactants and reagents mix in a solvent. Imagine a situation where the two liquids don't mix, and one floats due to its lower density!
Many such situations can be avoided by learning about a compound's physical properties. Going further, it would become easy to classify them based on their properties. A sulfur-containing compound gives a rotten odor; acetone evaporates at room temperature; a bromine-containing compound gives green flames when burned, and more. So, studying physical properties is usually the first step toward identifying and assessing a compound's purity.
The following chapter extensively covers the correlation between molecular structure and observed properties.
We learn how a molecule's structure - size and shape, geometry, symmetry, carbon numbers, functional groups, etc. can significantly affect its physical properties like melting point, boiling point, solubility, and density.
- Physical Properties- Introduction, Role of Intermolecular Forces
- Physical State Change-Melting Point
- Role of Symmetry, Role of Carbon numbers, Role of Geometry
- Physical State Change-Boiling Point
- Intermolecular Forces and their Effect on the Boiling Point, Role of Molecular Weight (Size), Molecular Shape, Polarity
- Boiling Point of Special Compounds- Amino acids, Carbohydrates, Fluoro compounds
- Solubility in Water
- Density