Chemistry: Mixtures and Solutions

Mixtures

• Mixtures are combinations of two or more substances where each substance retains its own chemical identity and properties.
• Mixtures are physically combined, not chemically bonded.
• Mixtures can be separated by physical means.

Types of Mixtures

• Homogeneous Mixtures: Components are uniformly distributed and consistent throughout.

  • Uniform appearance.
  • Single phase (solid, liquid, or gas).
  • Examples: Air, saltwater, solutions (sugar dissolved in water), alloys (brass).

• Heterogeneous Mixtures: Components are not uniformly distributed.

  • Non-uniform appearance.
  • Multiple phases.
  • Examples: Salad, suspensions (muddy water), colloids (milk, fog).

Solutions

• A specific type of homogeneous mixture.
• One substance (solute) is dissolved in another (solvent).
• Solutions have a uniform composition and properties throughout.
• Examples: Sugar dissolved in water.

Chemical Properties

• Describe how a substance interacts with other substances and its potential to undergo chemical changes.
• Intrinsic to the substance and can only be observed during a chemical reaction.
• Examples: Flammability, reactivity, acidity or basicity, oxidation state.

Chemical Changes

• Processes where substances undergo transformations to form new substances with different chemical properties.
• Involve the breaking and forming of chemical bonds.
• Examples: Combustion, oxidation, acid-base reactions, decomposition.

Characteristics of Solutions

• Solutions have a uniform composition, meaning the solute is evenly distributed throughout the solvent.
• They exist in a single phase, which can be solid, liquid, or gas.
• Solute particles are not visible to the naked eye as they are dispersed at the molecular or ionic level.

Components of Solutions

• The solute is the substance dissolved, typically present in a smaller amount than the solvent.
• The solvent is the substance that dissolves the solute, typically present in a larger amount.

Types of Solutions

• Solid Solutions: A homogeneous mixture with the solute dissolved in a solid solvent.
  • Examples: Alloys like bronze (copper and tin) and steel (iron and carbon).
• Liquid Solutions: A homogeneous mixture with the solute dissolved in a liquid solvent.
  • Examples: Saltwater (salt dissolved in water) and sugar water.
• Gas Solutions: A homogeneous mixture with gases dissolved in other gases.
  • Examples: Air, which is a mixture of gases, and carbonated beverages (carbon dioxide dissolved in liquid).

Properties of Solutions

• Concentration: The amount of solute in a given amount of solvent or solution.
  • Can be expressed as molarity, molality, or percentage.
  • Molarity (M): Moles of solute per liter of solution.
  • Molality (m): Moles of solute per kilogram of solvent.
  • Percentage Concentration: The mass or volume percentage of solute in the solution.
• Solubility: The maximum amount of solute that can dissolve in a given amount of solvent at a specific temperature and pressure.
  • Influenced by temperature, pressure, and the nature of the solute and solvent.
  • Solubility generally increases with temperature for solid solutes but decreases for gases.
  • Solubility of gases increases with pressure (Henry's Law).
• Saturation: A solution is saturated when it contains the maximum amount of solute that can dissolve at a specific temperature and pressure.
  • 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 dissolve, achieved by changing conditions like temperature.

Other Types of Mixtures

• Suspensions: Heterogeneous mixtures where solid particles are dispersed in a liquid, but settle out over time.

  • Particles are relatively large and visible.
  • Examples: Muddy water, orange juice with pulp.

• Colloids: Heterogeneous mixtures where particles are dispersed throughout another substance, but are small enough that they do not settle out.

  • Particles are intermediate in size, between solutions and suspensions.
  • Examples: Milk, fog, and gelatin.