chem paper 2💚

• Rate of reaction


  How quickly a reaction happens
• Measuring rate of reaction


  1. Reacting hydrochloric acid and sodium thiosulfate in a conical flask

  2. Measuring time until solution becomes cloudy

  3. Repeating at different temperatures
• Measuring rate of reaction

  1. Using a gas syringe to measure volume of gas produced

  2. Plotting a graph with quantity on y-axis and time on x-axis

  3. Drawing a tangent to find rate at any point
• Factors that increase rate of reaction

  • Increasing concentration of reactants
  • Increasing pressure of gas reactants
  • Increasing surface area of solid reactants
  • Increasing temperature
  • Adding a catalyst
• Reversible reactions


  Reactions where products can return to reactants
• Equilibrium


  Point where forward and reverse reaction rates are equal, so no overall change
• Increasing pressure


  Favours forward reaction in equilibrium
• Increasing temperature


  Favours endothermic (reverse) reaction in equilibrium
• Crude oil is the result of plankton being buried under water a long time ago
• Main components of crude oil

  • Hydrocarbons
  • Mostly alkanes
• Alkanes


  Molecules made up of only carbon and hydrogen, with a general formula of CnH2n+2
• Fractional distillation of crude oil

  1. Heating to evaporate and separate into fractions based on boiling points

  2. Shorter alkanes remain as gases at top

  3. Longer alkanes condense at different heights
• Fractions from fractional distillation

  • LPG
  • Petrol
  • Kerosene
  • Diesel oil
  • Heavy fuel oil
• Viscosity


  Thickness or resistance to flow of a liquid
• Longer alkane fractions have higher viscosity
• Alkenes


  Hydrocarbons with a carbon-carbon double bond
• Unsaturated


  Having a carbon-carbon double or triple bond
• Testing for alkenes


  Adding bromine water, which turns colourless if an alkene is present
• Cracking


  Breaking down longer alkanes into shorter alkanes and alkenes
• Catalytic cracking


  1. Using a zeolite catalyst at around 550°C

  2. Steam cracking at over 800°C with no catalyst
• Alcohols


  Organic compounds with an -OH functional group
• Reactions of alcohols


  1. Combustion to CO2 and H2O

  2. Reaction with sodium to form sodium alkoxide and hydrogen
• Carboxylic acids


  Organic compounds with a -COOH functional group
• Addition polymerisation


  Joining together monomers with double bonds, e.g. ethene to make polyethene
• Condensation polymerisation


  Joining together monomers with two functional groups, releasing water, e.g. alcohol and carboxylic acid to make polyester
• Amino acids


  Organic compounds with both an amino (-NH2) and a carboxyl (-COOH) group
• DNA


  Large molecule that stores genetic code, made from two polymer strands in a double helix
• Starch and cellulose


  Natural polymers made from glucose monomers
• Formulation


  A mixture designed for a specific purpose, with carefully controlled quantities of components
• Chromatography


  A technique for separating the components of a mixture
• DNA


  Made from two polymers that spiral around each other in a double helix and it's made from four different monomers called nucleotides
• Starch


  A natural polymer where the monomer is glucose
• Cellulose


  A polymer that's made from beta glucose
• Proteins


  Have amino acids as their monomers
• Melting point or boiling point


  • Indicates if a substance is pure - a pure substance will have a very specific melting or boiling point
• Formulation


  A mixture that has been specially designed to be useful in a very specific way with very specific quantities of different substances used to make things like paints, fuels, alloys, fertilizers
• Chromatography


  1. Separates substances in a mixture

  2. Stationary phase (often special chromatography paper or filter paper) is what the substances move up with the help of the mobile phase (often just water)

  3. Measure how far the solvent has moved and how far the substance(s) have moved to calculate an RF value (retention factor) which can be used to identify the substances
• Chemical tests


  1. Hydrogen - hold a burning splint over the test tube which will produce a squeaky pop

  2. Oxygen - will relight a glowing splint

  3. Carbon dioxide - will turn lime water cloudy when bubbled through it

  4. Chlorine gas - will bleach damp blue litmus paper

  5. Metals - flame tests (lithium crimson, sodium yellow, potassium lilac, calcium orange red, copper green)

  6. Aluminium, calcium, magnesium in solution - white precipitate with sodium hydroxide

  7. Copper 2+ ions - blue precipitate, Iron 2+ green precipitate, Iron 3+ brown precipitate

  8. Carbonates - react with acids to make carbon dioxide gas

  9. Halide ions - mix with silver nitrate solution and nitric acid (chloride white, bromide cream, iodide yellow)

  10. Sulfate ions - white precipitate with barium chloride and hydrochloric acid
• Instrumental methods


  Accurate, sensitive and fast methods used in proper labs to determine substances, e.g. flame emission spectroscopy
• The composition of gases in the atmosphere has changed over the course of the Earth's history