AQA Chemistry GCSE Topics 6-10
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AQA Chemistry GCSE Topics 6-10 - Marcador
AQA Chemistry GCSE Topics 6-10 - Detalles
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| State the collision theory | For a chemical reaction to occur, the reactant molecules must collide with enough energy |
| Activation energy definition | The minimum amount of energy needed for particles to react |
| Name the factors for increasing rate of reaction | Increasing temperature, increasing pressure, increasing surface area, adding a catalyst |
| What effect does temperature have on rate reaction? | Increasing temperature means: Particles move faster Particles collide more frequently More collisions creates more energy, increasing rate of reaction |
| What effect does pressure have on rate reaction? | Increasing pressure means: More particles in a set volume Particles collide more frequently More collisions creates more energy, increasing rate of reaction |
| What effect does surface area have on rate reaction? | Increasing surface area means: Higher surface to volume ratio Particles collide more frequently More collisions creates more energy, increasing rate of reaction |
| What effect does a catalyst have on rate on reaction? | Using a catalyst means: Provides an alternative reaction pathway with lower activation energy Activation energy needed decreases Reaction happens faster increasing rate |
| Equation to calculate rate of reaction | RofR = Amount of reactant or product formed/Time |
| Give 3 ways (excluding the equation) to measure rate of reaction | Disappearing mark through solution, change in mass (usually gas given off), volume of gas given off |
| Method for investigating effect of concentration on R of R by volume of gas produced [Method 1] | Set volume of dilute HCl acid in conical flask placed on mass balance Add magnesium ribbon and plug flask with cotton wool Start stopwatch and measure initial mass Take mass reading at regular intervals Plot on a graph [Loss in mass/Time] Repeat with different acid concentrations |
| Independent, dependent and control variables for concentration experiment Method 1 | Independent- concentration of acid Dependent- Loss in mass Control- Volume of acid, mass of magnesium ribbon |
| Method for investigating effect of concentration on R of R by change in colour [Method 2] | Set volume of dilute sodium thiosulphate in conical flask on paper with black X Add dilute HCl and start stopwatch Measure amount of time it takes for X to disappear Repeat reaction with different concentrations of either reactants [only one at a time] |
| Independent, dependent and control variables for concentration experiment Method 2 | Independent- concentrations of reactants Dependent- Time for X to disappear Control- Volume of reactants, black X |
| Conclusion for experiment | The higher the concentration, the faster the rate of reaction. |
| Mean rate of reaction = | Change in y / change in x |
| Reversible reaction definition | A reaction where the products can react to form the reactants |
| Name 2 reversible reactions | Ammonium chloride <=> Ammonia + hydrogen chloride Nitrogen + Oxygen <=> Nitric acid |
| Dynamic equilibrium definition | When both forward and backward reactions are happening at the same time but there is no overall effect |
| Define Le Chatelier's principle | If the conditions of a reversible reaction are changed at equilibrium, the system [where the reaction takes place] will try to counteract the change |
| Effect of changing temperature in a reaction system | Decreasing: Reaction shifts to exothermic direction to produce more heat More products for the exothermic reaction than the endothermic Increasing : Reaction shifts to endothermic direction to reduce heat More products for endothermic reaction than the exothermic reaction |
| Effect of changing the pressure in a reaction system | Increase: Equilibrium tries to reduce pressure Moves in direction where there are fewer molecules of gas Decrease: Equilibrium tries to increase pressure Moves in direction where there are more molecules of gas |
| Effect of changing the concentration in a reaction system | Any change in concentration: System tries to bring itself back to equilibrium Increase in reactants causes an increase in products Decrease in products causes a decrease in reactants |
| What is a hydrocarbon? | Any compound formed from only carbon and hydrogen atoms |
| What is crude oil? | A mixture made up of hydrocarbons of different lengths |
| What happens to the properties of hydrocarbons as chain length increases? | Become more viscous, less volatile, less flammable, higher boiling points |
| What are alkanes? | Saturated compounds with a C-C single bond |
| What are the first 4 alkanes? | Methane, Ethane, Propane, Butane |
| Chemical formulas of first 4 alkanes | CH4, C2H6, C3H8, C4H10 |
| General formula for alkanes? | CnH2n+2 |
| What is the equation for complete combustion of a hydrocarbon? | Hydrocarbon + oxygen ---> carbon dioxide + water + energy |
| Method of fractional distillation [for Crude oil] | Oil is heated until most is a gas Gases enter fractionating column Longer hydrocarbons with higher boiling points condense back into liquids and drain out of column early near the bottom Shorter hydrocarbons with lower boiling points condense and drain out later near the top of the column Mixture is separated into fractions containing hydrocarbons with similar numbers of carbon atoms |
| Method of cracking [catalytic] | Vaporise long chain hydrocarbons Vapour passed over hot powdered aluminium oxide as a catalyst Molecules split apart on the surface of the catalyst |
| What are alkenes? | Unsaturated compounds that have a double C=C bond |
| What products are produced when alkenes undergo incomplete combustion? | Carbon and carbon monoxide |
| When is hydrogen added to an alkene? | In the presence of a catalyst |
| When is an alcohol formed? | When an alkene reacts with steam and water is added in the presence of a catalyst |
| What are the uses of alkenes? | Alcohols, plastics, fuels, detergents |
| What are polymers? | A molecule comprised of long chains of monomers |
| What is addition polymerisation? | Where unsaturated monomer molecules open up their double bonds and join together to form polymer chains |
| What are the first 4 alcohols? | Methanol, Ethanol, Propanol, Butanol |
| What are the formulas for the first 4 alcohols? | CH3OH, C2H5OH, C3H7OH, C4H9OH |
| What do alcohols form when deoxidised? | Carboxylic acids |
| What is the mobile phase? | Where molecules can move |
| What is the stationary method? | Where molecules cannot move |
| What is an Rf value? | The ratio between the distance travelled by the dissolved substance [solute] and the distanced travelled by the solvent |
| Rf = | Distance travelled by substance [e.g ink spot] / distance travelled by solute [water or ethanol] |
| What is the test for chlorine? | Bleaches damp litmus paper |
| What is the test for oxygen? | Relights a glowing splint |
| What are the tests for carbon dioxide? | Puts out a lit splint Turns limewater cloudy when bubbled through |
| What is the test for hydrogen? | Creates a squeaky pop when lit splint held at the end of test tube containing hydrogen |
| Test for carbonate ions? | Add HCl acid to mystery solution connected to limewater If carbonate ions are present, carbon dioxide is formed turning the limewater cloudy |
| Test for sulphate ions? | Add HCl and Barium chloride solution to mystery solution If white precipitate is formed, sulphate ions are present |
| Test for halides? | Add dilute nitric acid and silver nitrate solution to mystery solution If chloride is present, white precipitate is formed If bromide is present, cream precipitate is formed If iodide is present, yellow precipitate is formed |
| Flame tests method | Sterilise platinum loop wire in HCl and blue flame Dip loop in sample and put in flame Record flame colour and sterilise Repeat with different samples |
| Lithium flame colour | Crimson |
| Sodium flame colour | Yellow |
| Potassium flame colour | Purple/ Lilac |
| Calcium flame colour | Orange-red |
| Copper flame colour | Green |
| Metal hydroxide test | Add sodium hydroxide to mystery compound forming insoluble hydroxide If coloured precipitate is formed this allows the metal to be identified |
| Aluminium precipitate colour | White then colourless |
| Composition of today's atmosphere | Approx: 80% nitrogen, 20% oxygen, small amounts of other gases |
| Composition of early atmosphere | Mostly carbon dioxide, minimal oxygen, nitrogen and small amounts of methane and ammonia |
| Theory of how early atmosphere formed | Surface covered in volcanoes that erupted releasing lots of gases |
| How did the early atmosphere become the present atmosphere? | Water vapour condensed forming oceans Oceans dissolved carbon dioxide Oxygen levels built up over time from photosynthesis |
| Describe non/renewable resources from the earth and atmosphere | Crude oil and fossil fuels from compressed layers of dead animals and sediment Geothermal power, hydropower, wind power, biomass |
| Potable water definition | Water safe for consumption |
| Potable water definition | Water that is safe for consumption |
| How is potable water produced? | Water is filtered through wire meshes to remove solids Water is then sterilised to kill harmful bacteria |
| Method to desalinate sea water | Test pH with pH meter Neutralise water if pH is too high or low with titration Complete a flame test to test for sodium ions [sodium chloride] If present flame will be yellow, so add dilute nitric acid and silver nitrate solution Heat in a distillation apparatus Water will evaporate leaving salts behind, and will condense into potable water Retest pH to ensure water is neutral |
| Differences in treatment waste water, salt water, ground water and sewage water | Waste water- must remove organic matter and harmful microbes Salt water- must be pH tested and distilled Ground water- filtered and sterilised Sewage water- must go through screening, sedimentation and anaerobic digestion |
| Phytomining definition | Where metals are extracted from their ions which are absorbed by plants through their roots |
| Bioleaching definion | Extraction of metals from their ores through the use of living organisms |
| Describe the process of phytomining | Plants absorb mineral ions Plants are harvested and burned producing ash Acid is added to ash to produce leachate Copper can be obtained through displacement with scrap iron |
| Describe the process of bioleaching | Bacteria are used to break down ores to produce leachate Copper ions in leachate are displaced by scrap iron |
| Advantages and disadvantages of phytoming | It is a slow process Reduces need of mining Conserves limited supply of high-grade ores Reduces rock waste |
| Advantages and disadvantages of bioleaching | Produces toxic substances Reduces need for mining Conserves high-grade ores Reduces rock waste |
| Purpose of the Haber process | Used to make ammonia for fertilisers |
| Haber process reaction | Nitrogen + hydrogen <=[iron catalyst]=> ammonia + heat N2 + 3H2 <=> 2NH3 + heat |
| When is the yield of ammonia higher? | When the temperatures are lower |
| What also increases the yield of ammonia? | Increasing pressure |
| What is the optimum operating pressure? | 200 atmospheres |
| What does the iron catalyst do? | Increase rate of reaction, doesn't affect yield |
| What is the trade off between rate of reaction and position of equilibrium? | Lower temperatures means the rate of reaction is slower and equilibrium is reached more slowly |
| What limits the Haber process commercially? | Expense of equipment to contain process safely, temperature of process and pressure process is completed under |
| What are NPK fertilisers? | Formulations of various salts including nitrogen, phosphorus and potassium at specific percentages |
| Describe the composition of NPK fertilisers | Comprised of nitrogen, phosphorus and potassium in specific percentages |
| How are NPK fertilisers made? | In the Haber process |
| How is ammonium sulphate [a fertiliser] made in a lab? | Drops of methyl orange indicator added to a set volume of ammonia sulfate solution in a conical flask Dilute sulfuric acid is added until turns orange When volume of sulfuric acid added is recorded then neutral ammonia sulfate with indicator is thrown away Experiment is repeated without indicator with same volumes of sulfuric acid and ammonia Ammonium sulfate is crystallised and then dried |
| What salt is produced when phosphate rock reacts with nitric acid? | Calcium nitrate and phosphoric acid |
| What salt is produced when phosphate rock reacts with sulfuric acid? | Single superphosphate |
| What salt is produced when phosphate rock reacts with phosphoric acid? | Triple superphosphate |