Types of Mixtures: Homogeneous vs Heterogeneous

• Chemistry involves the study of matter and its properties as well as how matter changes

Types Of Mixtures

• A mixture is a substance comprising two or more components that are not chemically bonded
• Mixtures can be either homogeneous or heterogeneous

Homogeneous Mixtures

• Homogeneous mixtures exhibit uniform composition and properties throughout
• Examples include saltwater, air, and sugar dissolved in water
• In a homogeneous mixture, individual components are not visible

Heterogeneous Mixtures

• Heterogeneous mixtures do not exhibit uniform composition
• Examples include sand and water, oil and water, and mixed nuts
• Different phases or regions with distinct properties are visible

Solutions

• A solution is a specific type of homogeneous mixture where one substance (solute) is dissolved into another (solvent)
• The solute is the substance that dissolves, and the solvent is the substance in which the solute dissolves
• Solutions can exist in various phases: solid, liquid, or gas

Properties of Solutions

• Solutions are homogeneous
• The solute is dispersed evenly throughout the solvent
• Solutions are generally transparent
• Solutes in a solution will not settle out over time
• The concentration of a solution can be varied

Solubility

• Solubility refers to the maximum amount of solute that can dissolve in a given amount of solvent at a specific temperature
• Solubility is affected by temperature, pressure, and the nature of the solute and solvent

Factors Affecting Solubility

• Temperature affects the solubility of solids, liquids, and gases
• The solubility of most solid solutes in liquid solvents increases with increasing temperature
• The solubility of gas solutes in liquid solvents typically decreases with increasing temperature
• Pressure significantly affects the solubility of gases
• The solubility of a gas in a liquid increases with increasing pressure (Henry's Law)

Solubility Principles

• "Like dissolves like" is a guiding principle for predicting solubility
• Polar solvents tend to dissolve polar solutes, while nonpolar solvents dissolve nonpolar solutes
• Water (H₂O) is a polar solvent and dissolves polar compounds like salt (NaCl) and sugar (C₁₂H₂₂O₁₁)
• Oil is a nonpolar solvent and dissolves nonpolar compounds like fats and waxes

Saturated, Unsaturated, and Supersaturated Solutions

• A saturated solution contains the maximum amount of solute that can dissolve in a solvent at a specific temperature
• An unsaturated solution contains less solute than the maximum amount that can dissolve in the solvent
• A supersaturated solution contains more solute than the maximum amount that can normally dissolve, achieved by changing temperature and is inherently unstable

Concentration Calculations

• Concentration is the amount of solute present in a given amount of solvent or solution
• Various methods are used to express concentration, including molarity, molality, percent composition, and parts per million (ppm)

Molarity (M)

• Molarity (M) is defined as the number of moles of solute per liter of solution
• M = moles of solute / liters of solution

Molality (m)

• Molality (m) is defined as the number of moles of solute per kilogram of solvent
• m = moles of solute / kilograms of solvent

Percent Composition

• Percent composition expresses the concentration as the percentage of solute in the solution
• Mass percent = (mass of solute / mass of solution) x 100

Parts Per Million (ppm)

• Parts per million (ppm) expresses the concentration as the number of parts of solute per million parts of solution
• ppm = (mass of solute / mass of solution) x 10^6

Dilutions

• Dilution involves reducing the concentration of a solution by adding more solvent
• The amount of solute remains constant during dilution
• The dilution equation is: M₁V₁ = M₂V₂ (where M is molarity and V is volume)

Separation Techniques

• Several techniques are used to separate mixtures into their individual components based on their physical properties
• Common separation techniques include filtration, distillation, evaporation, chromatography, and extraction

Filtration

• Filtration separates solid particles from a liquid by passing the mixture through a filter medium
• The solid particles are retained on the filter, while the liquid passes through

Distillation

• Distillation separates liquids with different boiling points
• The mixture is heated, and the component with the lower boiling point vaporizes first
• The vapor is then cooled and condensed back into a liquid

Evaporation

• Evaporation separates a soluble solid from a liquid by heating the solution to evaporate the liquid
• The solid remains as a residue

Chromatography

• Chromatography separates components of a mixture based on their different affinities for a stationary phase and a mobile phase
• Types of chromatography include paper chromatography, thin-layer chromatography (TLC), and gas chromatography (GC)

Extraction

• Extraction separates one or more components from a mixture using a solvent in which the desired components are more soluble
• Liquid-liquid extraction involves two immiscible liquids to separate components