chem paper 2

• Rate of reaction


  How quickly a reaction happens
• Mean rate


  The rate could be changing over the time you measure, but this is true for any measurement over time
• Experiment to measure rate of reaction

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

  2. Measuring the time taken for the solution to become cloudy and obscure a cross underneath

  3. Repeating at different temperatures
• As temperature increases


  The time taken for the reaction decreases
• Experiment to measure rate of reaction

  1. Measuring the volume of gas produced using a gas syringe

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

  3. Drawing a tangent to find the 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
• Catalyst


  Reduces the activation energy needed, so particles are more likely to collide successfully and react
• Reversible reaction


  Products can return to their original reactants
• Equilibrium


  The point where the rates of the forward and reverse reactions are equal, so there is no overall change
• Increasing pressure


  Favours the forward reaction, shifting the equilibrium to the right
• Increasing temperature


  Favours the endothermic (reverse) reaction
• In a reversible reaction, if the forward reaction is exothermic, the reverse reaction must be endothermic, and vice versa
• Crude oil


  Mixture of hydrocarbons formed from buried plankton
• Alkanes


  Hydrocarbons with single carbon-carbon bonds, formula CnH2n+2
• Fractional distillation of crude oil

  1. Heating to evaporate and separate fractions by boiling point

  2. Shorter alkanes remain as gases at the top

  3. Longer alkanes condense at lower heights
• LPG


  Liquid petroleum gases, containing alkanes up to 4 carbons
• Viscosity


  Measure of a liquid's thickness or resistance to flow, longer alkanes are more viscous
• Alkenes


  Hydrocarbons with carbon-carbon double bonds
• Unsaturated


  Containing a carbon-carbon double bond
• Testing for alkenes


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


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


  1. Using a zeolite catalyst at 550°C

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


  Organic compounds with an -OH functional group
• Carboxylic acids


  Organic compounds with a -COOH functional group
• Esters


  Compounds formed by the reaction of an alcohol and a carboxylic acid
• Amino acids


  Contain both an amino (-NH2) and a carboxyl (-COOH) group
• DNA


  Deoxy-ribonucleic acid, a polymer made from nucleotide monomers
• 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


  It's 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


  A way to tell if a substance is pure or not
• 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. Separating sub substances in a mixture

  2. Stationary phase (often special chromatography paper or filter paper)

  3. Mobile phase (often just water) rises up the paper due to capillary action dragging lighter particles further up

  4. Draw a line at the bottom in pencil so it doesn't move with the solvent

  5. Measure how far the solvent has moved and how far the substance(s) have moved to calculate an Rf value (retention factor)
• Rf value is a ratio of how far a spot has moved compared to the solvent, between 0 and 1
• Rf values can be compared to known Rf values to identify what's in the mixture
• Testing for hydrogen


  Hold a burning splint over the test tube which will produce a squeaky pop