2C1.1 Fundamental ideasAtomic Number = The number of protons in each atom of an element e.g. oxygen = 8.Mass Number = The number of protons AND neutrons in each atom of an element e.g. oxygen = 16.Mass Number will always be the bigger number.In an atom the number of protons = number of electrons. (This is why atoms are always neutral…no overall charge)Number of neutrons = Mass number - Atomic number
3C1.2 Limestone and it usesLimestone is a rock made of calcium carbonate (CaCO3). Metal carbonates undergo thermal decomposition (they break down when heated) producing carbon dioxide:CaCO3 → CaO + CO2A rotary kiln does this on a huge scale to make calcium oxide from limestone.Metal carbonates also react with acid to make a salt, water and carbon dioxideCaCO3 + 2HCl → CaCl2 + H2O + CO2We test for carbon dioxide gas by bubbling it through limewater and seeing if it goes cloudy. Limewater is calcium hydroxide and reacts with CO2 to make calcium carbonate which is insoluble.Ca(OH)2 + CO2 → CaCO3 + H2O.Calcium hydroxide is made by adding water to calcium oxideCaO + H2O → Ca(OH)2These reactions represent the limestone cycle opposite (except the one with acid)The limestone cycle:Cement is a mixture of clay and calcium oxide. When mixed with sand and water it makes mortar. If we add small stones as well it becomes concrete. Concrete hardens over time as it reacts with CO2 to become CaCO3 again. Concrete can be made even stronger by reinforcing it with steel rods. Limestone is quarried in areas of countryside. This can be a nuisance as it scars the landscape and creates a lot of noise and dust but creates lots of jobs bringing money to an area.
4C1.3 Metals and their usesAn ore is a rock that contains enough of the metal to make it worth extractingAluminium is a very light metal. It is extracted by electrolysis of aluminium oxide. This is very expensive as it needs a lot of electricity. Aluminium is unreactive as the metal forms a protective coating of aluminium oxide. Recycling aluminium is very important as it saves energy/fuel, conserves ores and does not waste space in landfill.Three ways of extracting metals from their ores.Reduction with carbonElectrolysisDisplacementTitanium is much stronger than aluminium but even more expensive to make as it isextracted by displacement with Mg.1. Any metals lower than carbon in the reactivity series can be obtained by reduction with carbon. The metal oxide is reduced (loses oxygen) to give the metal and CO2.Copper is extracted by smelting:Copper Sulfide + Oxygen → Copper + Sulfur DioxideThe copper is then purified by electrolysis to make very pure copper for electrical wiring.Low-grade ores contain small amounts of copper. We extract the copper from these by using bacteria (bioleaching) or plants to absorb the copper into their roots (phytomining). We harvest and burn the plants to get the copper. Both of these green methods take a long time.Iron Oxide + Carbon → Iron + Carbon DioxideZinc Oxide + Carbon → Zinc + Carbon DioxideIron is obtained from iron oxide by heating with carbon in a blast furnace. Steel is an alloy of iron as the metal contains more than one element (iron + carbon). Alloys are much stronger than the pure metal. Stainless steel is very useful as it does not corrode.We can make an alloy of any metal tochange it’s properties (eg strength)
5C1.4 Fuels from Crude OilFractional distillation separates crude oil into fractions containing similar sized hydrocarbon molecules. The crude oil is vaporised at high temperature and passed into a fractionating column. The column is hot at the bottom and cool at the top. As the vapour rises up the column, different fractions condense at their boiling point and are collected. Big hydrocarbonshave high boiling points and arecollected at the bottom of the column.Small hydrocarbons have low boilingpoints and are collected at the topof the column.Alkanes are hydrocarbons – they contain carbon and hydrogen only.Monkeys Methane CH4Eat Ethane C2H6Peanut Propane C3H8Butter Butane C4H10Alkanes have the formula CnH(2n+2)Burning hydrocarbons in oxygen produces carbon dioxide and water.ALKANE + OXYGEN CARBON DIOXIDE + WATERWe can use this show this with this equipment:The carbon dioxide will turn the limewater cloudyThe water will condense in the U-tube and cause any indicator to change colour.
6C1.4 Green ChemistryBurning fossil fuels releases carbon dioxide, CO2. Carbon dioxide is a greenhouse gas. It traps heat in the earth’s atmosphere and causes global warming.Burning diesel also produces particulates (soot) – these small carbon particles.Burning hydrocarbons in oxygen produces carbon dioxide and water.ALKANE + OXYGEN CARBON DIOXIDE + WATERWe can show this with the set-up below:The carbon dioxide will turn the limewater cloudyThe water will condense in the U-tube and cause any indicator to change colour.
7C1.5 Products from OilCracking = Big alkane Small alkane + Small AlkeneOctane Hexane EtheneHow? Heat and catalystWhy? Turn useless big alkanes into small alkanes(fuel) and alkenes (to make polymers and ethanol)Smart polymers have properties which change depending on their surroundings e.g. shrink as they warm upUnsaturated – alkene - C=C double bondsBromine water tests for these. This is orange but goes colourless if C=C present.If bromine water stays orange its alkane – saturated – C-C bonds onlyPlastic waste is a big problem. We can:Burn it to provide energy (but that’s dirty)Recycle and make into other productsDump as landfill (not very green)Plastics from crude oil do not break down. We can make biodegradable plastics from plants (PLA - cornstarch) which do break down. These are also renewable (unlike plastics from crude oil) but people may starve as less land used to grow food.Polymerisation:Many small molecules (monomers)joined togetherto make very large molecules (polymer)Ethanol : From plants or oil?Hydration (from oil):Ethene + Steam EthanolFermentation (from plants):Glucose Ethanol + Carbon dioxidemonomer polymerethene poly(ethene)n is a very large number
8C1.6 Plant Oils2 methods of extracting plant oilsPressingSteam DistillationEmulsions: Mixture of two immiscible liquids (oil and water).Examples: Mayonnaise, Milk, PaintWhy? Nicer, thicker texture. Good coating ability (dipping chips in sauce)How? Add emulsifier – chemical that forces oil and water to mix…Unsaturated means C=C double bondsBromine water tests for these. This is orange but goes colourless if C=C present.Cooking with oils (frying):Good: Nice taste and textureEnergy richNutrients eg Vitamin EQuick (higher temperature)Bad: Make you fat if eat too muchHydrophilic headattracted towaterHydrophobic tailattracted to oilEmulsifier EmulsionHardening: Turn oils to solid fat (margarine)Why? Make spreadableHow? Hydrogen / 60oC / Nickel catalystUnsaturated fats (C=C) good for youSaturated fats (C-C only) bad for youMonounsaturates have one C=CPolyunsaturates have more than one C=CE numbers are food additives…chemicals added as emulsifiers, preservatives or for colourUnsaturated SaturatedC=C C-CHardening oils increases melting point so solid at room temperature
9C1.7 Our changing planetVolcanoes formed our early atmosphere which was mainly water vapour and carbon dioxide. The water vapour condensed and formed the oceans. The carbon dioxide has been ‘locked up’ in carbon sinks (sedimentary rock, fossil fuels, oceans). Plants also changed carbon dioxideinto oxygen during photosynthesis.Radioactive decay in the core releases heat which causes convection currents in the mantle. Tectonic plates can move on these currents.Wegener believed South America and Africa were joined together a long time ago. He believed this because:Coastlines fit together like a jigsawSimilar layers of rock on both coastlines.Similar fossils on both coastlines.The carbon cycle balances the amount of carbon dioxide in the atmosphere. Burning fossil fuels is upsetting the carbon cycle causingglobal warming and makingthe sea more acidic.Fractional distillation is used to separate the gases in air. They are cooled to make liquid air (the solid carbon dioxide and water are removed) and then warmed up slowly so they boil one at a time.In the Miller-Urey experiment they showed it was possible to make organic compounds from simple molecules in the early atmosphere (hydrogen, ammonia, water and methane) but they cannot make living things. Other possibilities are meteors or developed in volcanic vents under the sea.primordialsoupThe edges of tectonic plates are called plate boundaries. We can get earthquakes or volcanic eruptions at these but it is difficult to predict them as we cannot see under the earth’s surface.