Chemistry: Mixtures and Their Types

Mixtures: A Physical Combination

• Mixtures are combinations of two or more substances where each component retains its own chemical identity.
• Components are not chemically bonded, but rather physically combined.
• Mixtures can have variable composition and the components can be separated using physical methods (filtration, centrifugation, evaporation).

Types of Mixtures

Homogeneous Mixtures

• Components are uniformly distributed throughout the mixture.
• Have a consistent composition throughout.
• Typically exist in a single phase (solid, liquid, or gas).
• Examples: air, saltwater, solutions, alloys

Heterogeneous Mixtures

• Components are not uniformly distributed, resulting in different compositions in different regions of the mixture.
• May have distinct regions or phases with varying compositions.
• Can consist of multiple phases (solid, liquid, or gas).
• Examples: salad, muddy water (suspensions), milk, fog (colloids)

Solutions: Homogeneous Mixtures

• Solutions are a specific type of homogeneous mixture where a solute is dissolved in a solvent.
• Have a uniform composition and properties throughout.
• Solute particles are dispersed at the molecular or ionic level and are not visible to the naked eye.

Components of Solutions

• Solute: substance that is dissolved in the solvent, usually present in a smaller amount
• Solvent: substance that dissolves the solute, usually present in a larger amount.

Types of Solutions

Solid Solutions

• Solute is dissolved in a solid solvent.
• Examples: alloys like bronze (copper and tin) and steel (iron and carbon), solid-solid solutions (mixture of metals)

Liquid Solutions

• Solute is dissolved in a liquid solvent.
• Examples: saltwater, sugar water

Gas Solutions

• Gases are dissolved in other gases.
• Examples: air (a mixture of nitrogen, oxygen, and trace gases), carbonated beverages (carbon dioxide gas dissolved in liquids)

Properties of Solutions

Concentration

• Refers to the amount of solute dissolved in a given amount of solvent or solution.
• Can be expressed in various ways:
  • Molarity (M): moles of solute per liter of solution
  • Molality (m): moles of solute per kilogram of solvent
  • Percentage Concentration: mass or volume percentage of solute in the solution

Solubility

• Maximum amount of solute that can dissolve in a given amount of solvent at a specific temperature and pressure.
• Factors affecting solubility:
  • Temperature: generally increases with temperature for solids, decreases for gases
  • Pressure: increases with pressure for gases (Henry's Law)
  • Nature of Solute and Solvent: depends on the chemical nature of the solute and solvent (polar vs. nonpolar)

Saturation

• A solution is saturated when it contains the maximum amount of solute that can dissolve at a given temperature and pressure.

• Types of Solutions:

  • Saturated Solution: Contains the maximum amount of solute that can dissolve
  • Unsaturated Solution: Contains less solute than the maximum amount that can dissolve
  • Supersaturated Solution: Contains more solute than the maximum amount that can normally dissolve achieved by changing conditions such as temperature

Other Types of Mixtures

Suspensions

• Heterogeneous mixtures with relatively large, visible solid particles dispersed in a liquid.
• Particles will settle out if left undisturbed.
• Examples: muddy water, orange juice with pulp

Colloids

• Heterogeneous mixtures with particles intermediate in size between solutions and suspensions.
• Particles are small enough that they do not settle out.
• Examples: milk, fog, gelatin