Physical Changes and Properties Summary

Physical Changes

• Definition: A process where a substance changes its physical appearance but not its chemical composition.
• Example: Ice cube melting (solid water to liquid water) – the identity remains as water (H₂O).

Types of Physical Changes

• Melting: Solid to liquid (e.g., ice to water).
• Boiling: Liquid to gas.
• Freezing: Liquid to solid.
• Sublimation: Solid to gas without a liquid phase (e.g., dry ice in water creating steam).

Physical Properties vs. Chemical Properties

• Physical Property: Can be observed without changing the identity of the substance.
  • Examples of Physical Properties:
  • Density (e.g., Lithium: 0.534 g/mL at 20°C).
  • State (e.g., Liquid at 200°C).
  • Consistency (e.g., Soft consistency).
• Chemical Property: Involves chemical changes and alters the identity of the substance.
  • Example of Chemical Property: Reacts vigorously with water (upon reaction, lithium changes identity).