Physical vs Chemical Changes

  • A physical change is a change in the form of a substance, not in its chemical composition = reversible

         ○ A physical change can be used to separate a mixture into pure compounds, but will not break

compounds into elements

              ■ Ex: phase changes, separation techniques (Distillation, filtration, chromatography), dissolving

        ○ Involve changes in intermolecular forces

       ○ Physical properties: shape, solubility, density, volume, & interparticle distance at diff temperatures (& phases) may change but composition stays the same

  • Chemical change: a substance becomes a new substance with different properties and composition

        ○ Ex: rusting, bunsen burner (burning), acid, combustion (reacted with oxygen)

        ○ Evidence of chem change: temp, light, electrical conductivity, or color change; gas or precipitate formation

        ○ Justify: bonds have been broken and new bonds have been formed → involve changes in intramolecular forces

Example: Dissolving NaCl

  • Can be argued both ways bcuz is reversible (physical change) and ionic bonds are broken (chemical)