Pure Substances and Mixtures

• Pure substances consist of a single type of particle and have the same chemical properties.
• Mixtures contain two or more pure substances and can be physical combinations:
  • Homogeneous mixtures (solutions): uniform composition (e.g., saltwater).
  • Heterogeneous mixtures: non-uniform composition (e.g., oil and water).

Types of Mixtures

• Solutions: Homogeneous mixtures like lemonade; solute is dissolved in the solvent.
• Suspensions: Heterogeneous mixtures where particles are visible and can settle (e.g., sand in water).
• Colloidal solutions: Particles are dispersed but not settled, showing the Tyndall effect (e.g., milk).

Properties of Mixtures

• In mixtures, constituent properties are retained, and the composition can vary.
• Mixture components can be separated by simple physical methods.
• Solutions have solute/solvent components, while suspensions and colloids are heterogeneous.

Concentration of Solutions

• Concentration can be expressed as:
  1. Mass by mass % = (Mass of solute / Mass of solution) × 100
  2. Mass by volume % = (Mass of solute / Volume of solution) × 100
  3. Volume by volume % = (Volume of solute / Volume of solution) × 100
• Saturated solution: maximum solute dissolved at a given temperature.

Changes in Matter

• Physical changes: Do not alter the chemical composition (e.g., changes in state).
• Chemical changes: Result in new substances through reactions (e.g., burning).

Types of Pure Substances

• Elements: Basic forms of matter cannot be broken down. Examples include metals (e.g., iron) and non-metals (e.g., oxygen).
• Compounds: Substances made of two or more elements chemically combined in fixed proportions (e.g., water).

Important Definitions

• Constituents: The components of mixtures or compounds.
• Filtration: A method to separate solids from liquids in mixtures.
• Tyndall Effect: Scattering of light by colloidal particles indicating the presence of colloids in a solution.