OCR GCSE Chemistry C1a-h

C1a - Making Crude Oil UsefulHydrocarbon = contains hydrogen and carbon atoms only (Key word examiners look for)3 types of fossil fuels: Crude Oil Coal Natural Gas 3 problems associated with the finite nature of crude oil: All readily extractable resources used up Finding replacements Conflict between making petrochemicals and fuels Hydrocarbon with: 1 Carbon = Methane (MY) 2 Carbons = Ethane (ELEPHANT) 3 Carbons = Propane (POOS) IN LPG 4 Carbons = Butane (BRICKS) IN LPG 5 Carbons = Pentane (PLEASE) 6 Carbons = Hexane (HELP) Fractions in crude oil (from top of column to bottom): LPG (LITTLE) Petrol (PURPLE) Paraffin (PUFFINS) Diesel (DANCE) Heating Oil (HOME) Lubricating Oil (LEAVING) Fuel Oil (FOOTPRINTS) Bitumen (BEHIND) Non-renewable = resource is being used up faster than it can be formed (e.g. crude oil)Finite = Resource is no longer being made or is being made extremely slowlySmaller Fractions: Smaller molecules have weaker intermolecular forces Require less energy to break Lower boiling points Larger Fractions: Larger Molecules have stronger intermolecular forces Require more energy to break Higher boiling points During boiling the intermolecular forces between molecules break, but the covalent bonds do not.Political problems associated with the exploitation of Crude Oil: UK dependent on Oil from politically unstable countries Future supply issues Environmental problems involved in the transportation of Crude Oil: Detergents used to clean up Oil Slicks can cause damage to wildlife Damage to bird's feathers causing death Alkene = carbon-carbon double bond (un-saturated) (Test for an alkene = bromine water will decolourise) CnH2nAlkane = no carbon-carbon double bond (saturated) Cn H2n+2Cracking: Helps to make more Petrol Conditions required are a high temperature and a catalyst Converts large alkane molecules into smaller alkane and alkene molecules Makes useful alkene molecules that can be used to make polymers Long un-useful hydrocarbons (in high supply yet low demand) are broken down into smaller hydrocarbons (in low supply yet high demand) e.g. Bitumen to Petrol

C1b - Using Carbon FuelsCombustion = When fuels react with oxygen in the air and release useful heat energyIncomplete combustion = When fuels burn without enough oxygen and some heat energy is released, but not as much as complete combustionComplete Combustion of Methane: Bold = subscriptMethane (CH4) + Oxygen (2O2) →Carbon Dioxide (CO2) + Water (H2O)Incomplete Combustion of Methane:Methane (2CH4) + Oxygen (3O2) →Carbon monoxide (2CO) + Water (H2O)7 Factors of fuels in order to choose the best for a particular purpose: (TEACUPS / ACEPETS) Energy Value Availability Ease of storage Cost Toxicity Pollution Ease of Use The blue Bunsen flame releases more energy than the yellow flame.Increasing amount of fossil fuels being burnt because of: Increasing world population Increased use in developing countries, such as China

C1c - Clean AirHow does _____ effect the level of carbon dioxide in the air? Combustion? Increases Respiration? Increases Deforestation? Increases Photosynthesis? Decreases Increasing population? Increases The 4 components of air: Oxygen (21%) Nitrogen (78%) Water Vapour (0.035%) Carbon Dioxide These levels are approximately constant.Balanced symbol equation for how a catalytic converter removes carbon monoxide from exhaust fumes:2CO + 2NO →N2 + 2CO2Possible theory for how the present day atmosphere evolved over millions of years: Degassing of early volcanoes producing an atmosphere rich in water and carbon dioxide Condensing of water vapour to form oceans Dissolving of carbon dioxide in ocean waters Relative increase of nitrogen due to its lack of reactivity Development of photosynthetic organisms Increase in oxygen levels due to photosynthesis

C1d - Making PolymersCovalent bond = a shared pair of electronsDouble Covalent bond = 2 shared pairs of electronsThe addition polymerisation process:Many alkene monomer molecules react together to give a polymer which requires high pressure and a catalystWhy does bromine water decolourise in the presence of an alkene?An addition reaction occurs that forms a colourless dibromo compoundWhy is Methane/Ethane/Propane/Butane/Pentane/Hexane an alkane?It only contains single covalent bonds between carbon atomsUnsaturated = a compound which contains at least one double covalent bond between carbon atomsSaturated = a compound which contains only single covalent bonds between carbon atomsFormation of a polymer:Many small molecules (monomers) join together in a polymerisation reaction

C1e - Designer PolymersEnvironmental and economic issues related to the use and disposal of polymers: Uses up valuable land in landfill Can ham/kill wildlife Burning release toxic gases Burning is a waste of resources What properties of polyethene allows it to be used for plastic bags? Light Flexible Easily Moulded Can be easily printed on What properties of polyester allows it to be used for waterproof jackets? Lightweight Waterproof Tough Can be coloured Blocks UV light What properties of polystyrene allows it to be used to hold hot liquids? Light Poor conductor of heat What properties of nylon allows it to be used for tents? Lightweight Waterproof Tough Blocks UV light Plastics that have weak intermolecular forces have what properties? Low melting points Can be stretched easily as the polymer molecules can slide over one another Plastics that have covalent bonds or cross-linking bridges have what properties? High melting points Cannot be stretched and are rigid Main properties of nylon: Tough Lightweight Keeps water and UV light out, but does not let water vapour through it which means that sweat condenses Main properties of Gore-Tex: Same as nylon + is breathable Membrane = PTFE, not used on its own because its too fragile Holes in membrane are too small for water to pass through but are big enough for water vapour to pass through Methods of disposing polymers: Use of land-fill sites Burning Recycling Why are chemists developing... polymers that bio-degrade? so that they can degrade faster in landfill polymers that dissolve? so that they can increase their range of uses (e.g. dishwasher tablets) Non-biodegradable = Will not decay or decompose by bacterial action

C1f - Cooking and food additivesEmulsifiers = prevent oil and water from separating (e.g. In mayonnaise) Hydrophilic head (binds to water molecules) and Hydrophobic tail (binds to oil molecules)Food is a chemical change because: A new substance is formed The process cannot be reversed An energy change takes place Why is a potato easier to digest if cooked? Cell walls rupture resulting in loss of rigid structure Starch grains swell up and spread out Why does the texture of an egg change when cooked?Protein molecules permanently change shape and denatureFunction of Antioxidants = stops food reacting with oxygen and gives it a longer lifeFood colouring, Flavour enhancers, Antioxidants and Emulsifiers are all examples of food additivesSodium Hydrogencarbonate is heated = Thermal decomposition, results in sodium carbonate, carbon dioxide and water(Sodium Hydrogencarbonate → Sodium Carbonate + Carbon dioxide + water / 2NaHCO3 → Na2CO3 + CO2 + H2O)How does baking soda help cakes to rise? Sodium hydrogencarbonate thermally decomposes, which produces carbon dioxide, which helps cake to riseChemicals in food affected by cooking: Proteins Carbohydrates

C1g - SmellsSoluble substance = Dissolves in a liquid (e.g. nail varnish is will dissolve in ethyl ethanoate)Insoluble substance = Doesn't dissolve in a liquid (e.g. nail varnish does not dissolve in water)Volatile = Evaporates easilySolvent = The liquid in which a substance is dissolved (e.g. ethyl ethanoate)Solute = The substance that gets dissolvedSolution = Result of mixing a solvent and a soluteWhy does nail varnish not dissolve in water?The attraction between water molecules and the attraction between nail varnish molecules is stronger than the attraction between water molecules and nail varnish moleculesHow to make an ester: (A family of compounds often used as perfumes and in solvents)React an alcohol with an organic acidAnother name for manufactured perfumes = Synthetic perfumesMain necessary properties of perfumes: Smell Nice Evaporate easily Not be Toxic Non-irritant Insoluble Not reactive with water Why are perfumes volatile?The molecules of perfume are held by weak forces of attraction, the molecules with lots of energy can easily overcome these weak forces and escapeDisadvantages of animal testing: Cruel to animals Different body chemistry so test results may be invalid Advantages of animal testing: Prevent harming humans Test if medicines are safe New drugs have to be tested to make sure they are safe: The drugs are tested using computer models and human cells grown in the laboratory. Drugs that pass the first stage are tested on animals. A typical test involves giving a known amount of the substance to the animals, then monitoring them carefully for any side-effects. Drugs that have passed animal tests are used in clinical trials. They are tested on healthy volunteers to check they are safe. The substances are then tested on people with the illness that the drugs are designed to treat to ensure that they are safe and work properly. Perfumes from natural sources: Lavender Musk Rose

C1h - Paints and PigmentsPaint = a colloid, the particles of pigment are mixed and dispersed with particles of a liquid but are not dissolved, they do not separate out because they are too smallOil based paint = Pigments are dissolved in an oil, which may be dissolved in a solvents.Oil Paints dry in 2 steps: The solvent evaporates The oil is oxidised by atmospheric oxygen Emulsion Paints dry in 2 steps: Paints are apllied as thin layer The solvent (water) evaporates A thermochromic paint changes colour when heated or cooled, acrylic paint can be added to thermochromic pigments to give thermochromic paints more colour changesUses for thermochromic pigments: Babies bath toys Kettle Thermometers A phosphorescent pigment can glow in the dark, phosphorescent pigments are used rather than radioactive alternatives because they are much saferA phosphorescent pigment glows in the dark because they absorb and store energy and then release it as light over a period of time3 components of paint: Binder = Sticks pigment in paint to surface Solvent = Thins the paint and makes it easier to spread Pigment = Gives the substance its colour