2Contents Useful Products from Oil Useful Products from Metal Ores Useful Products from RocksUseful Products from AirRepresenting ReactionsQuantitative ChemistryChanges to the Earth and AtmosphereThe Rock Record
3Useful Products From Oil What is crude oil?Fractional distillationCracking and its productsFuelsPlastics
4What is crude oil?Crude oil is a mixture of a very large number of compounds.It is formed from the remains of plants and animals which died millions of years ago. This is why it is called a fossil fuel.Most of the compounds in crude oil consist of molecules made up of hydrogen and carbon atoms only, we call these type of compounds hydrocarbons.We represent hydrocarbons in the following ways:
5Fractional Distillation The many hydrocarbons in crude oil may be separated into fractions, each of which contains molecules of a similar size, by evaporating the oil and allowing it to condense at a number of different temperatures. This process is called fractional distillation.
6Cracking and its Products There is a much greater demand for shorter hydrocarbon than there is for the longer hydrocarbons.Long chain hydrocarbons can be broken into smaller hydrocarbons, by heating with a catalyst.This is a thermal decomposition reaction known as cracking.Cracking produces two types of hydrocarbonAlkanes with only single covalent bondsAlkenes with one or more double covalent bondsTest for alkenes: alkenes turn bromine water from brown to colourless.
7FuelsMost fuels contain carbon and/or hydrogen and may also contain some sulphur. The gases released into the atmosphere when a fuel burns may include:carbon dioxide;water (vapour), which is an oxide of hydrogen;sulphur dioxideThis gas dissolves in rain and forms acid rain.
8PlasticsAlkenes are reactive and so are useful for making many other substances including polymers. Polymers have very large molecules. They are formed when many small molecules join together. This process is called polymerisation.When alkenes join together to form a polymer with no other substance being produced in the reaction, the process is called addition polymerisation.Plastics are polymers and are made by polymerisation.For example, poly(ethene) (often called polythene) is made by polymerising the simplest alkene, ethene.
9Useful Products from Rocks Metal Ores and ReactivityThe Blast FurnaceExtraction of AluminiumPurification of CopperCorrosion
10Metals Ores and Reactivity Rocks from the Earth contain many useful metals.Most metals are combined with other elements in materials called ores and have to be extracted using various methods.How each metal is extracted depends on how reactive it is.Gold is a very unreactive metal and is found as a pure metal, because of this it has been in use for many thousands of years despite of being a very rare metal.Iron and copper are more reactive than gold but less reactive than carbon, these can be extracted from their ores by simply heating with coke these have been known for several thousand yearsAluminium is the most common metal in the Earth’s crust, however, was only discover 200 years ago because it is a relatively reactive metal which is hard to extract from its ore.
11Extracting iron using the blast furnace. A metal such as iron, which is less reactive than carbon, can be extracted from its ore using carbonReactions in the blast furnace.C + O2 CO2The coke burns, to form carbon dioxide and to produce heatCO2 + C 2COThe carbon dioxide reacts with more hot coke to produce carbon monoxide gas.3CO + Fe2O3 2Fe + 3CO2The carbon monoxide removes the oxygen from the iron ore this is called reduction.The main impurity in the iron ore is silica this reacts with the limestone to produce slag (calcium silicate)
12Extraction of Aluminium Aluminium is made by the electrolysis of bauxite.Cryolite is added to lower the melting point of bauxite.This is a very expensive process and aluminium is only made in this way because it cannot be prepared by heating with carbon because it is too reactiveAt the negative electrodeAl3+ + 3e- Al (REDUCTION)At the positive electrode2O2- O2 + 4e- (OXIDATION)
13Purification of Copper Copper can be extracted from its ore by reduction with carbon, however, this is only 98% pure.Copper can be purified by electrolysis using a positive electrode made of the impure copper and a negative electrode of pure copper in a solution containing copper ions.When the current is switched on copper ions in solution are attracted to the negative and electrode and deposited there. Copper atoms in the impure block lose electrons and become positive ions and go into the solution, replacing those which were deposited at the negative electrode.Eventually the impure block disappears leaving behind the impurities and the pure block becomes larger.
14Corrosion Iron rusts in the presence of oxygen and water. Barriers such as paint or grease can be used to prevent corrosion.Zinc blocks can be attached to iron objects. As zinc is more reactive than iron it will corrode preferentially thus preventing the iron from corroding. This is called sacrificial protectionAluminium is a very reactive metal but it can be used without protection against corrosion. This is because it has a thin lay of oxide which sticks very firmly to the aluminium and protects it against further corrosion.
16Useful Products from Air Manufacture of ammonia from airManufacture of fertiliser from ammoniaProblems caused by the over use of fertilisers.
17Manufacture of ammonia from air Nitrogen and Hydrogen are needed to make Ammonia.Nitrogen is obtained from the air.Hydrogen is obtained from water and natural gas.The Haber process is a reversible reactionThis means that the reaction occurs in both directionsHigh pressures favour the production of ammonia, however it expensive to make industrial equipment to cope with high pressures.Low temperatures favour the production of ammonia, however at low temperatures the reaction would be too slow to be commercially viable.The Haber process makes a compromise with these two and recycles the unreacted hydrogen and nitrogenN2(g) + 3H2(g) Â 2NH3(g)
19Problems cause by the over use of fertiliser Plants need several types of nutrients. Nitrogen based nutrients are used to make proteins.Farmers can use natural sources of these nutrients or synthetic nutrients.If fertilisers are over used the excess can wash into streams. Plants and green algae grow out of control. When they, die bacteria feed off of the dead plant material The bacteria increase in number, they use up all the oxygen in the water. Then the fish die. This process is called eutrophication.Too many nitrates in the drinking water can also cause problems. It can interfere with the blood’s ability to carry oxygen. This can be especially severe in children and babies, causing them to turn ble and even die.
20Representing Equations When we can represent reactions by word and symbol equations:methane + oxygen carbon dioxide + wateror CH4 + O2 CO2 + H2OTo this we can add state symbols to give more information about the substances:(s) – solid, (l) – liquid, (g) – gas, (aq) – aqueousCH4(g) + O2(g) CO2(g) + H2O(g)This doesn’t tell us the whole story we need to balance the equation to show that we have not destroyed or made new atoms.
21Balancing Equations CH4(g) + O2(g) CO2(g) + H2O (g) Remember that the formulae for each compound is correct you cannot change CH4 to CH3 just to make the atoms add up.Balance one type of atom at a time:There is one carbon atom on each side so we can leave that alone, however there are 4 H atoms on the left hand side and 2 on the right hand side we can correct this by putting a 2 in front of the water.CH4 (g) + O2 (g) CO2 (g) + 2H2O (g)Now both the carbon and the hydrogen balance, that just leaves us with the oxygen. There are 2 O on the left hand side and 4 on the right hand side. We can correct this by putting a 2 in front of the oxygen on the left hand side:CH4 (g) + 2O2 (g) CO2 (g) + 2H2O (g)
23Calculating Masses Relative Atomic Mass Relative Molecular Mass This is the mass number that you find on the periodic table.Relative Molecular MassThis is the sum of all therelative atomic masses of all of the atoms in a compound e.g.
24The MoleOne mole of atoms or molecule of any substance will have a mass in grams equal to the relative atomic mass or relative molecular mass for that substance.The atomic mass of carbon is 12, therefore one mole of carbon weighs 12gThe relative molecular mass of oxygen (O2) is (2 x 16) 23, therefore one mole of oxygen weighs 32g.One mole of any substance contains 6.02 x 1023 atoms or molecule.Remember the mole is just a number!
25Reacting MassesBy using the relative molecular masses in grams we can deduce what masses of reactants to use and what mass of products will be formed.
26Changes to the Earth and Atmosphere 4.5 billion years agoWhen the Earth first formed, its surface was molten. As it cooled surface rocks formed. An atmosphere formed from volcanic gases: carbon dioxide, steam, ammonia and methane.3 billion years agoThe Earth cooled enough for the steam to condense and form the oceans. The main gas in the atmosphere was carbon dioxide. Simple plants evolved.2 billion years agoThe first plant produced oxygen, this killed off many other life forms.1 billion years agoThe excess oxygen in the atmosphere reacted in the presence of UV light to form ozone. This ozone filtered out most of the damaging UV light and allowed more complicated life forms to evolve.The present timeThe atmosphere is approximately 1/5 oxygen and 4/5 nitrogen.carbon dioxide is absorbed by plants, shellfish and dissolved in the oceans.It is given out by burning fuels, the decay of organic waste and released from volcanoes.ammonia in the air reacted with oxygen to form nitrogen. More nitrogen was formed by bacteria in the soil.
28Summary Useful Products from Oil Useful Products from Metal Ores Crude oil is a mixture of hydrocarbons. The can be separated and processed by cracking and polymerisation to make a variety of useful materialsUseful Products from Metal Oreshow we obtain metals depend on how reactive the areUseful Products from RocksLimestone can be used as building material or as a raw material in cement, concrete and glass.Useful Products from AirNitrogen from the atmosphere can be turned into synthetic fertiliser. Overuse cause eutrophicationRepresenting Reactionspractice balancing equationsQuantitative ChemistryPractice lots of these problems.Changes to the Earth and AtmosphereThe first atmosphere was mainly carbon dioxide. Plant produced all the oxygen in the atmosphere. This oxygen formed ozone which protects us from uv light.The Rock RecordRocks contain evidence of how they were formed. Different types of rock are linked in the rock cycle.