Overview
This lecture explains the differences between physical and chemical properties, giving examples of each and clarifying how to identify them.
Physical Properties
- Physical properties describe characteristics that do not change the chemical identity of a substance.
- Examples include boiling point, melting point, and freezing point; changes in state are physical changes.
- Ductility (ability to be drawn into wires) is a physical property because the substance remains chemically unchanged.
- Malleability (ability to be hammered into sheets) is a physical property since the substance's chemical identity stays the same.
- Color is a physical property unless a color change indicates a chemical reaction.
- Viscosity (resistance of a fluid to flow) is a physical property as it describes flow, not reactivity.
- Density (mass per unit volume), mass, weight, and volume are all physical properties.
Chemical Properties
- Chemical properties describe characteristics that involve changing the chemical identity of a substance.
- Flammability is a chemical property because burning produces new substances.
- Corrosiveness is a chemical property since it involves chemical reactions (e.g., acids corroding metals).
- Combustibility and explosiveness are chemical properties because they involve chemical reactions.
- pH is a chemical property, related to the acidity or basicity and how substances react.
- Taste is a chemical property since it involves reactions with the body's receptors (e.g., acids taste sour).
Key Terms & Definitions
- Physical Property — a characteristic of a substance that does not involve changing its chemical identity.
- Chemical Property — a characteristic that can only be observed by changing the chemical identity of a substance.
- Boiling Point — the temperature at which a substance changes from liquid to gas.
- Ductility — the ability of a material to be pulled into wires.
- Malleability — the ability of a material to be hammered into sheets.
- Viscosity — a fluid's resistance to flow.
- Density — mass per unit volume of a substance.
- Flammability — the ability of a substance to burn or combust.
- Corrosiveness — the ability of a substance to cause destructive chemical reactions.
- pH — a measure of acidity or basicity.
- Combustibility — ability to burn in the presence of oxygen.
Action Items / Next Steps
- Review and memorize examples of physical and chemical properties.
- Practice identifying whether properties are physical or chemical for common substances.