chem

• Matter can be broken down into pure substances (constant composition like elements and compounds) and impure substances (variable composition like mixtures)
• Elements contain one type of atom only, while compounds are made up of elements chemically combined in a fixed ratio
• Impure substances, like mixtures, are made up of components that are not chemically combined and are in no fixed ratio. Mixtures can be separated by physical means
• Mixtures can be heterogenous (non-uniform composition) or homogenous (uniform composition)
• A solution is a homogenous mixture where a solute completely dissolves in a solvent. Examples include copper (II) sulphate solution, saline solution, and alloys
• A suspension is a heterogenous mixture where a solute does not dissolve in a solvent, and particles settle out on standing. Examples include calcium carbonate and water, and flour suspended in water
• A colloid is a heterogenous mixture where a solute does not dissolve in a solvent, and particles remain suspended in the solution. Examples include smoke, dust, and blood
• An emulsion is a heterogenous mixture where a liquid is suspended in another liquid. Examples include mayonnaise, milk, and salad dressing
• Properties of types of mixtures:

  • Size of particles: Solution (0.01-1 nm), Suspension (>1000 nm), Colloid (1-1000 nm)
  • Sedimentation of particles: Solution (Particles dissolve), Suspension (Particles settle on standing), Colloid (Particles remain suspended)
  • Ability to be separated by filtration: Solution (Cannot be separated), Suspension (Easily separated), Colloid (Cannot be separated)
  • Effect when light is shone through mixture: Solution (Light easily passes through), Suspension (Light does not easily pass through), Colloid (Light is scattered - Tyndall effect)
  • Appearance: Solution (Transparent), Suspension (Opaque), Colloid (Translucent)
• Solubility is the maximum mass of a solute that can saturate 100 g of solvent at a particular temperature and pressure
• Factors affecting solubility:

  1. Temperature: Increase in temperature usually increases the mass of solute that dissolves

  2. Polarity of solute and solvent: Like dissolves like - polar solutes dissolve in polar solvents and non-polar solutes in non-polar solvents

  3. Pressure: Increase in pressure increases solubility of gaseous solutes
• Solubility curves can be plotted to show the solubility of solutes at different temperatures
• Separation techniques include:

  • Gravity Filtration and Decanting
  • Simple Distillation and Fractional Distillation
  • Paper Chromatography
  • Separating Funnel
• Separation techniques for mixtures include:

  • Simple Filtration
  • Decanting
  • Sublimation
  • Solvent Extraction
  • Evaporation
  • Fractional Distillation
  • Simple Distillation
  • Use of Separating Funnel
  • Chromatography
  • Centrifugation
• Sublimation:

  • Type of mixture: Solid in solid
  • Principles: One solid sublimes while the other does not
  • Example: Ammonium chloride and sodium chloride mixture
• Solvent Extraction:

  • Type of mixture: Solid in solid (solutions)
  • Principles: One solid is more soluble in a solvent, and solvents are immiscible
  • Example: Iodine and sodium chloride
• Evaporation:

  • Type of mixture: Solid in liquid (Solutions)
  • Principles: Liquids evaporate on heating while solids do not
  • Example: Sodium Chloride in water
• Separation technique: Simple distillation

  Type of mixture: Solid in liquid (solutions)

  Principles:

  • Components have boiling points that differ significantly

  Example: Sodium chloride and water

  Explanation:

  • As the apparatus is heated to 100°C, the water will evaporate to form water vapor
  • Sodium chloride (boiling point 1413°C) will remain in the round-bottomed flask
  • Water vapor enters the condenser, cools, and forms water
• Separation technique: Fractional distillation

  Type of mixture: Liquid in liquid (solution)

  Principles:

  • Components have boiling points that are different but fairly close

  Example: Ethanol (boiling point 76°C) and water (100°C)

  Explanation:

  • Apparatus heated to 76°C, ethanol evaporates and is collected after cooling
  • Water may evaporate, condense in the fractionating column, and re-enter the flask
  • Apparatus then heated to 100°C for water to evaporate and be collected
• Separation technique: Separating funnel

  Type of mixture: Liquid in liquid

  Principles:

  • Immiscible liquids with different densities

  Example: Oil and water

  Explanation:

  • Oil and water are immiscible, do not dissolve in each other
  • Oil, less dense, floats on water
  • Stopcock allows water to be collected first, then oil
• Separation technique: Simple filtration

  Type of mixture: Solid in liquid

  Principles:

  • Particles in suspensions are too large to pass through filter paper

  Example: Calcium carbonate (chalk) and water

  Explanation:

  • Calcium carbonate particles too large to pass through filter paper, remain as residue
  • Water molecules pass through filter paper, collected as filtrate
• Separation technique: Paper chromatography

  Type of mixture: Colloidal dyes and pigments

  Principles:

  • Different solubilities of components in a particular solvent

  Examples: Chlorophyll, Black Dye

  Explanation:

  • Solvent travels up paper, components dissolve
  • More soluble components travel farther, less soluble remain closer to origin
• Separation technique: Decanting

  Type of mixture: Solid in liquid

  Principles:

  • Particles in suspension settle out

  Example: Sand and water

  Explanation:

  • Sand settles at the bottom
  • Liquid poured off carefully
• Separation technique: Centrifugation

  Type of mixture: Suspensions

  Principles:

  • Centrifugal force promotes sedimentation

  Examples: Separating red blood cells from blood

  Explanation:

  • Spinning force forces particles to the bottom
  • Less dense components poured off, pellet retained
• Extraction of sucrose from sugarcane involves several separation techniques:

  1. Crushing: Sugarcane cut, crushed to extract juice, and screened to remove large fibers

  2. Precipitation/Clarification: Calcium hydroxide added to reduce acidity, impurities settle out

  3. Filtration: Settled particles filtered from clarified juice

  4. Evaporation: Clarified juice heated to remove excess water, converted to thick syrup

  5. Vacuum Crystallization: Syrup boiled in vacuum pans to produce molasses and sugar crystals

  6. Centrifugation: Centrifuge separates sugar crystals from molasses
• Uses of waste materials from sucrose extraction:

  • Bagasse (waste fibers): Bio-fuel, pulp, building materials, animal feed
  • Molasses: Animal feed, baking, candy, vinegar production
• Cations:

  • 1+ Charge: H+ (hydrogen), Na+ (sodium), K+ (potassium), Li+ (lithium), Cu+ (copper(I)), Ag+ (silver)
  • 2+ Charge: Mg2+ (magnesium), Ca2+ (calcium), Ba2+ (barium), Zn2+ (zinc), Cu2+ (copper(II)), Pb2+ (lead(II)), Fe2+ (iron(II)), Mn2+ (manganese (II))
  • 3+ Charge: Al3+ (aluminum), Fe3+ (iron(III)), Cr3+ (chromium(III))
• Anions:

  • 1– Charge: H- (hydride), F - (fluoride), Cl - (chloride), Br - (bromide), I - (iodide)
  • 2– Charge: O2- (oxide), S2- (sulphide), SO4 2- (sulphate), SO3 2- (sulphite), NO3 - (nitrate), CO3 2- (carbonate), NO2 - (nitrite), C2O4 2- (oxalate), OH - (hydroxide), CH3COO - (ethanoate), HCO3 - (hydrogen carbonate), HSO4 - (hydrogen sulphate)
  • 3– Charge: PO4 3- (phosphate), P3- (phosphide), N3- (nitride)
• Common Molecules:

  • Diatomic Molecules ("Special Seven"): H2 (Hydrogen), O2 (Oxygen), F2 (Fluorine), Br2 (Bromine), I2 (Iodine), N2 (Nitrogen), Cl2 (Chlorine)
  • Miscellaneous Common Molecules: H2O (water), H2O2 (hydrogen peroxide), CH3COOH (ethanoic acid), NH3 (ammonia), HNO3 (nitric acid), CH4 (methane), H2SO4 (sulphuric acid), CO2 (carbon dioxide), H3PO4 (phosphoric acid), CO (carbon monoxide), H2CO3 (carbonic acid), NaCl (salt or table salt)
• Common Acids: HCl (hydrochloric acid), NaCl (salt or table salt)