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)