This Matter Around Us is Pure

Definition of Pure Substance

• Pure Substance: Substances that are made up of only one type of particles (atoms or molecules).
• Examples:
  • Copper - made up of only copper atoms.
  • Water (H2O) - made up of only H2O molecules.

Impure Substance

• Impure Substance: Substances that are made up of different types of particles.
• Examples:
  • When salt is added to water, water becomes impure.
  • Impure substances are also called mixtures.

Types of Pure Substances

• Elements: Made up of only one type of atoms. (Examples: Copper, Iron, Oxygen)
• Compounds: Made up of two or more types of atoms in a fixed ratio. (Examples: Water, Carbon Dioxide - CO2)

Mixture

• Mixture: A combination of two or more substances which can be uniform or non-uniform.

  Types:

  • Homogeneous Mixture: In which all components are uniformly mixed. (Example: Sugar and Water)
  • Heterogeneous Mixture: In which all components are not uniformly mixed. (Example: Water and Oil)

Solution

• Example of Homogeneous Mixture: Like lemonade, sugar solution.

• Solute: The substance which dissolves.

• Solvent: The substance in which others dissolve.

  Properties:

  • Particles are very small, invisible to the naked eye.
  • Do not scatter light.
  • Solvent and solute cannot be separated by filtration.
  • As temperature increases, solubility of the solute also increases.

Saturated and Unsaturated Solutions

• Unsaturated Solution: More solute can be dissolved.
• Saturated Solution: No more solute can be dissolved.

Concentration

• Two methods to calculate the concentration of a solution:
  • Mass by Mass Percentage: [\text{Mass percentage} = \frac{\text{Mass of Solute}}{\text{Mass of Solution}} \times 100]
  • Mass by Volume Percentage: [\text{Mass by Volume percentage} = \frac{\text{Mass of Solute}}{\text{Volume of Solution}} \times 100]

Colloidal and Suspension Solutions

• Colloidal Solutions: Small particles that do not settle. Example: Milk.
• Suspensions: Large particles that settle over time. Example: Muddy water.

Tyndall Effect

• Scattering of light making the path of light visible.
• Solution: Does not show Tyndall effect.
• Colloidal Solution: Shows Tyndall effect.
• Suspension: Shows Tyndall effect.

Summary

• Concept of pure and impure substances.
• Types of mixtures and their properties.
• Properties of Solutions, Colloidal solutions, and Suspensions and the differences among them.
• The Tyndall effect and its significance.

In the next section, we will study further aspects of this chapter.