AQA Chemistry Unit 1

1. AQA Chemistry Unit 1 This PowerPoint supports section C1.4, C1.5, C1.6 and C1.7 sections of the AQA Chemistry Unit 1 module

2. Crude Oil

3. Hydrocarbons and crude oil H H C C H H H H Ethane Increasing length H H H H C C C C H H H H H H Butane Crude oil is a mixture of HYDROCARBONS (compounds made up of carbon and hydrogen). Some examples: Longer chains mean… Less ability to flow Less flammable Less volatile Higher boiling point

4. Distillation revision This apparatus can be used to separate water and ink because they have different _____ ______. The ______ will evaporate first, turn back into a _______ in the condenser and collect in the _______. The ink remains in the round flask, as long as the _______ does not exceed ink’s boiling point. This method can be used to separate crude oil. Words – temperature, boiling points, water, beaker, liquid

5. Fractional distillation Fractions with low boiling points condense at the top Fractions with high boiling points condense at the bottom Crude oil can be separated by fractional distillation. The oil is evaporated and the hydrocarbon chains of different lengths condense at different temperatures:

6. Alkanes H H C C H H H H Ethane H H H H C C C C H H H H H H Butane • Alkanes are SATURATED HYDROCARBONS. What does this mean? • HYDROCARBONS are molecules that are made up of hydrogen and carbon atoms • SATURATED means that all of these atoms are held together by single COVALENT bonds, for example: Alkanes are fairly unreactive (but they do burn well). The general formula for an alkane is CnH2n+2

7. General Formulae for Alkanes H H H H H H H C C C C C C C H H H H H H H H H H H H H Methane (n=1) Ethane (n=2) H H H C C C H H H H H Propane (n=3) Butane (n=4) Instead of circles, let’s use letters… General formula for alkanes = CnH2n+2

8. Burning Fossil Fuels H H H O O O O O O O O H H C C H H H sulfur + oxygen sulfur dioxide Burning fossil fuels like oil and coal causes pollution. Oil contains carbon: Carbon dioxide is a “greenhouse gas” – it helps cause global warming Coal contains carbon, sulfur and other particles: Sulfur dioxide causes acid rain. Other particles can cause “global dimming” – sunlight is absorbed by the particles in the atmosphere.

9. Removing Sulfur Sulfur dioxide is clearly bad for the environment so it’s a good idea to remove as much sulfur as possible: Vehicles can remove sulfur from fuels before they are burned. Power stations can remove sulfur dioxide from waste gases after combustion.

10. Other fuel sources • Task: Identify two other fuel sources (“biofuels”) currently being developed and find out the following: • What is the source called and what is it made of? • Why is the fuel better than coal? • What are the disadvantages of this fuel?

11. Using Crude Oil Benefits Drawbacks Plastics don’t biodegrade Cheap to extract Burning fossil fuels causes pollution Crude Oil Wide range of uses as fuel Used to make plastics Disposal of materials uses up land fill sites It’s going to run out

12. Disposal of plastics 1) Landfill sites - most plastics do not _________ which means that landfill sites are quickly filled up. Research is being carried out on __________ plastics. 2) Burning – this releases carbon dioxide which causes the ________ effect, as well as other ________ gases. 3) _______ – the best option, but difficult because of the different types of plastic Words – recycling, greenhouse, decompose, biodegradable, poisonous

13. Ethanol Ford Escape E85 – runs on 85% ethanol Ethene + steam ethanol Sugar ethanol + carbon dioxide Ethanol is an important chemical. Many countries are increasing the amount of ethanol put into their petrol supplies: Ethanol is a “clean burning” energy source and produces little or no greenhouse gases. How is it made and what are the advantages and disadvanatges of each method? The “fossil fuel” way Ethene is produced by “cracking” oil The “renewable” way Sugar is produced from standard crops like sugar cane and corn

14. Making ethanol from ethene Ethene + water ethanol Unused ethene recycled C2H + H20 C2H5OH Reaction vessel with high temperature and pressure and a catalyst Ethene Ethanol

15. Cracking Ethene Butane Ethane For example, this bond can be “cracked” to give these: Shorter chain hydrocarbons are in greater demand because they burn easier. They can be made from long chain hydrocarbons by “cracking”:

16. Cracking Gaseous hydrocarbon Long chain hydrocarbon Heated catalyst Liquid hydrocarbon This is a THERMAL DECOMPOSITION reaction, with clay used as a catalyst Cracking is used to produce plastics such as polymers and polyethanes. The waste products from this reaction include carbon dioxide, sulfur dioxide and water vapour. There are three main environmental problems here: • Carbon dioxide causes the _________ effect • Sulfur dioxide causes _____ _____ • Plastics are not _____________

17. Alkenes ALKANES ALKENES Ethene Ethane Butane Butene Alkenes are different to alkanes; they contain DOUBLE COVALENT bonds. For example: This double bond means that alkenes have the potential to join with other molecules – this make them REACTIVE. Alkenes turn bromine water colourless.

18. Testing for alkenes Bromine water Bromine goes colourless Oil

19. General Formulae for Alkenes H H C C H H Ethene (n=2) H H H H H H H C C C C C C C H H H H H H H Propene (n=3) Butene (n=4) General formula for alkenes = CnH2n

20. Monomers and Polymers H H C C H H Ethene This molecule is called POLYETHENE, and the process that made it is called POLYMERISATION Here’s ethene again. Ethene is called a MONOMER because it is just one small molecule. We can use ethene to make plastics… Step 1: Break the double bond Step 2: Add the molecules together:

21. Another way of drawing it… H H H H C C C C H H H H Ethene Ethene Poly(e)thene H H H H C C C C H H H H n C C n C C C C CH3 CH3 H H e.g. n C C n H H H H Instead of circles, let’s use letters… General formula for addition polymerisation:

22. Some examples H H H H n C C n H H H H H H H H n C C n H H Cl Cl Cl Cl H H C C C C C C n C C n H H Br Br

23. Uses of addition polymers Poly(ethene) Poly(propene) Poly(styrene) Poly(chloroethene), PVC

24. Biodegradable carrier bags This carrier bag has been made with flax fibre from industrial waste.

25. Measuring Energy in Food The energy content in foods is measured in Joules and calories Foods with large carbohydrate and fat contents have lots of energy, but too much energy and too little exercise could lead to obesity.

26. Vegetable Oils When plants photosynthesise they produce glucose. They can also produce vegetable oils and we can use these for food and fuel:

27. Extracting Oil Step 2: Remove oil by pressing Step 1: Crush the plant OR step 3: Remove oil by distillation

28. Why use oil for cooking? • Why do we use oil for cooking and not just water? • What are the problems associated with using oil in cooking?

29. Healthy and Unhealthy Oils Unhealthy oils: “Saturated” Healthy oils: “Unsaturated”

30. Saturated vs. Unsaturated Fats H H C C H Bromine water H Ethene Bromine goes colourless Oil (in ethanol) Some oils are more healthy than others. Fish oils contain the nutrients Omega-3 and Omega-6. These oils are “unsaturated” like ethene: Testing for double bonds: Clearly, it is important for scientists to be able to test if a food contains “healthy” unsaturated fats or “unhealthy” saturated fats. Here’s how it’s done:

31. Turning unsaturates into saturates 600C, Nickel catalyst The unsaturated fat is hardened by “hydrogenation”. Hydrogenated oils have a higher melting point and so are solid at room temperature, making them useful for spreads and pastries.

32. Emulsions Butterfat Watery liquid Milk Cream Butter What’s an emulsion? It’s a mixture of oil and water, like in salad dressing… Paint is an emulsion. Other examples:

33. Why use emulsions? Different thicknesses of cream Paint and mayonnaise Emulsions can have varying textures and this makes them useful. Some examples:

34. Emulsifiers An emulsifier is an additive that will stop oil and water from seperating, like in mayonnaise. How they work: I’m an emulsifier – I’ll sort this out with my hydrophobic end and my hydrophilic end! I don’t want to mix with you! Water Oil The water and oil drops become “coated” and insulated from one another, which prevents them from separating.

35. Uses of emulsifiers in food • Emulsifiers are used: • In bread, to stop large _____ developing when it bakes • In low fat spreads, to allow the oil and water to be _____ • In ice cream and spray cream, to ______ the foam • In sponge cakes, to make tiny pockets of ____ • In chocolate, to stop melted chocolate forming _______ Words – crystals, air, holes, mixed, stabilise

36. The Structure of the Earth A thin crust - 10-100km thick A mantle – has the properties of a solid but it can also flow A core – made of molten nickel and iron. Outer part is liquid and inner part is solid The average density of the Earth is much higher than the crust, so the inner core must be very dense

37. Movement of the Lithosphere These plates are moving apart from each other a few centimetres every _______ due to the ________ currents in the mantle caused by the ________ decay of rocks inside the core. The Earth’s LITHOSPHERE (i.e. the _______) is split up into different sections called ________ plates: Words – radioactive, crust, convection, tectonic, year

38. Plate Movements Oceanic Crust Mantle Convection Currents Earthquakes and volcanic eruptions can be common here Magma

39. The Earth’s Atmosphere Carbon dioxide, water vapour Oxygen Nitrogen Noble gases For the last 200 million years the atmosphere has remained roughly the same – it contains 78% nitrogen, 21% oxygen, 1% noble gases and about 0.03% CO2

40. Evolution of the Earth’s Atmosphere Carbon Methane Ammonia Oxygen Nitrogen Others dioxide 4 Billion years 3 Billion years 2 Billion years 1 Billion years Present day Present day atmosphere contains 78% nitrogen, 21% oxygen, 1% noble gases and about 0.03% CO2

41. Evolution of the Earth’s Atmosphere Volcanic activity releases CO2, methane, ammonia and water vapour into the atmosphere. The water vapour condenses to form oceans. 4 Billion years 3 Billion years 2 Billion years 1 Billion years Present day Green plants evolve which take in CO2 and give out oxygen. Carbon from CO2 becomes locked up in sedimentary rocks as carbonates and fossil fuels. Methane and ammonia react with the oxygen and nitrogen is released. Some of the oxygen is converted into ozone. The ozone layer blocks out harmful ultra-violet rays which allows for the development of new life.

42. One theory about how life was formed… The “Primordial Soup” theory: A collection of simple molecules like methane In 1953 I conducted an experiment that proved that an electrical discharge can turn methane into amino acids! This is called the “Miller-Urey experiment”. Amino acids Dr Stanley Miller 1930-2007

43. Carbon dioxide in the atmosphere The amount of CO2 in the atmosphere is affected by 3 things: 1) Geological activity moves carbonate rocks deep into the Earth and they release ______ _______ into the atmosphere during volcanic activity. 2) When fossil fuels are burned the carbon contained in them reacts with _____ to form CO2. 3) Increased CO2 in the atmosphere causes a reaction between it and _______. These reactions do not remove ALL of the new CO2 so the greenhouse effect is still getting _______! Words – oxygen, seawater, carbon dioxide, worse

44. Separating air Remove CO2 and H2O vapour Oxygen Liquid air (-200OC) Fractional distillation Argon Nitrogen In this chamber the air is gradually heated up again and the different parts of air “distil” off at different temperatures according to their boiling points Air can be separated into the different gases that make it up. To do this you first have to cool air down to -2000C and turn it into a liquid:

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