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23/05/2017 Chemistry 1 The structure of the atom 23/05/2017 Electrons in shells Neutron in nucleus Proton in nucleus Mass and atomic number 23/05/2017 Particle Relative Mass Relative Charge Proton 1 +1 Neutron 1 0 Electron Almost 0 -1 MASS NUMBER = number of protons + number of neutrons SYMBOL PROTON (ATOMIC) NUMBER = number of protons (or electrons) Symbols Elements are represented by symbols 23/05/2017 Elements, compounds & mixtures 23/05/2017 Elements – contain one type of atoms Mixtures – two or more elements not chemically joined Compounds – two or more elements chemically joined Periodic table 23/05/2017 Reactive metals Non-metals Transition metals Noble gases Other metals Separates metals and non-metals H Li Be Na Mg Columns called groups Mendeleev He B C N O F Ne Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Rows called periods Electron structure Potassium has 19 electrons. These electrons occupy specific energy levels “shells”… The inner shell has 2 electrons The next shell has 8 electrons The next shell has 8 electrons The next shell has the remaining 1 electron Electron configuration = 2.8.8.1 Nucleus 23/05/2017 Compounds Compounds are formed when two or more elements are chemically combined. Some examples: 23/05/2017 Methane Sodium chloride (salt) Glucose Covalent bonding 23/05/2017 Atoms sharing electrons is called covalent BONDING. This bonding occurs between nonmetals atoms. Each atom make enough covalent bonds to fill it’s outer shell Hydrogen has just 1 electron in its outer shell. A full (inner) shell would have 2 electrons, so two hydrogen atoms get together and “share ” their electrons: Now they both have a full outer shell and are more stable. The formula for this molecule is H2. Ionic bonding 23/05/2017 This is where a metal bonds with a non-metal. Electrons are transferred between atoms. Metal atoms lose electrons to form positive ions Non-metals gain electrons to form negative ions Na Sodium in Group 1 has 1 electron on its outer shell Cl Chlorine in Group 7 has 7 electrons in outer shell. Sodium transfers 1 electron – so both atoms have a full outer shell and are stable. Positive and negative charges attract + A positively charged sodium ion Na Cl A negatively charged chloride ion Limestone Limestone is a sedimentary rock made up of mainly calcium carbonate. It’s cheap and easy to obtain by quarrying. Uses Building materials Making cement. CaCO3 heated with clay Making mortar. Cement mixed with sand and water Making concrete. Cement mixed with sand and aggregate Neutralising acidic soil & lakes - slaked lime 23/05/2017 Limestone Positives of quarrying • Provides jobs • Provides materials • Provides neutralisation products 23/05/2017 Negatives of quarrying • Destroys habitats • Produces noise and dust • Transportations makes pollution • Destroys landscape The “Limestone Cycle” 23/05/2017 Calcium Carbonate (CaCO3) + water Step 1: CaCO3 heated – thermal decomposition Step 3: add carbon dioxide to slaked lime calcium hydroxide Ca(OH)2 (slaked lime) Step 2: add water to quicklime calcium oxide + carbon dioxide CaO (quicklime) + CO2 Metal extraction 23/05/2017 Metals above carbon extracted by electrolysis below carbon extracted by reduction silver and gold found native increasing reactivity Metals can either be found native in the ground (e.g. gold) or are found as metal ores (e.g. iron = haematite, aluminium = bauxite) potassium sodium calcium magnesium aluminium carbon zinc iron lead copper silver gold Reduction Reduction is the removal of oxygen The metal ore is reacted with carbon. The carbon is more reactive so removes the oxygen from the ore iron oxide + carbon carbon dioxide + iron 23/05/2017 carbon zinc iron lead copper Electrolysis Electrolysis is breaking down a substance using electricity It needs a liquid to conduct electricity. High temperatures are needed, which needs a lot of energy making it expensive Positive electrode made of impure copper – loses Cu2+ ions = shrinks + + + + Cu2+ Cu2+ - Solution containing copper ions 23/05/2017 potassium sodium calcium magnesium aluminium carbon Negative electrode made of pure copper – gains Cu2+ ions = grows Bioleaching & phytomining 23/05/2017 New mining techniques used to extract copper and decrease the effects of metal extraction on the environment. Bioleaching uses bacteria to separate copper from copper sulphide. The solution produced (leachate) contains copper which can be filtered. Phytomining uses plants grown in soil containing copper, which builds up in leaves. Leaves burnt and copper in ash can be collected. Recycling metals Fossil fuels running out Recycling uses less energy than mining Recycling saves money Recycling cuts down on landfill sites Recycling reduces amount of pollution Properties of metals 23/05/2017 • Strong • Can be bent • Can be hammered • Good conductors of heat and electricity Li Be Na Mg Al K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Copper, Aluminium and Titanium 23/05/2017 Metal Properties Uses Copper Good electrical conductor, hard, strong, can be bent, doesn’t react with water Electrical wires, plumbing pipes and tanks Aluminium Corrosion resistant, low density, forms hard alloys Aeroplanes Titanium Low density, very strong, corrosion resistant Hip replacements Alloys 23/05/2017 An “alloy” is a mixture of metals. Alloys are harder than pure metals Gold mixed with copper Aluminium mixed with magnesium and copper Aluminiun mixed with chromium Using Iron 23/05/2017 Iron produced by the blast furnace contains about 96% iron and 4% impurities. These impurities make it very brittle and easy to break. Iron is alloyed to make steel. Steel with a low carbon content is easily shaped Steel with a high carbon content is strong but brittle Steel with chromium and nickel is called stainless steel Crude oil Crude oil is a mixture of hydrocarbons (only contains elements hydrogen and carbon) The separate parts – fractions – can be extracted by fractionating distillation Crude oil piped in at bottom of fractionating column, heated, oil evaporates and rises. Fractions condense and are collected 23/05/2017 D e c r e a s i n g t e m p e r a t u r e Alkanes 23/05/2017 Alkanes are saturated hydrocarbons - all of the atoms are held together by single bonds. General formula is CnH2n+2 - twice as many hydrogen atoms as carbon atoms plus an extra two Methane – CH4 Propane – C3H8 Ethane – C2H6 Butane – C4H10 Patterns 23/05/2017 Increasing length Longer chains mean… 1. More viscous (gloopy) 2. Less flammable 3. Higher boiling point Fuels A fuel is burned to release energy Coal, oil and gas are fossil fuels. 23/05/2017 Burning Fossil Fuels 23/05/2017 Burning fossil fuels (combustion) releases gases and particles Complete combustion (plenty of oxygen) produces carbon dioxide and water H H C H O O H O C O H O H O O O H H Carbon dioxide is a “greenhouse gas” – cause global warming Incomplete combustion (not enough of oxygen) produces carbon monoxide and carbon H H C H H O C O Carbon monoxide is a poisonous gas O Sulphur dioxide 23/05/2017 Burning coal releases sulphur dioxide and nitrogen oxides Sulphur dioxide and nitrogen oxides cause acid rain and “global dimming” – sunlight is absorbed by the particles in the atmosphere. Acid rain kills trees, causes lakes to become acidic killing wildlife and damage limestone buildigns and statues Alternative fuels Fuel Pros 23/05/2017 Cons Ethanol – made from plant material Carbon neutral – CO2 Engines need to be used for plant to grow. converted. Isn’t Other waste product is widely available yet. water Biodiesel – made from vegetable oils Carbon neutral. Expensive to make, Engines don’t need to would increase food be converted. Produces prices less SO2 Hydrogen gas – made from water Very clean – no pollution Need special, expensive engines. Isn’t widely available. Need to use energy to make it. Cracking 23/05/2017 Useful short chain hydrocarbons can be made from long chain hydrocarbons by “cracking”: Gaseous hydrocarbon Long chain hydrocarbon Heated catalyst Liquid hydrocarbon Long chain hydrocarbon heated to thermally decompose. Hydrocarbon vaporises, passes over a catalyst and splits into an alkane and an alkene Alkenes 23/05/2017 Alkenes are unsaturated hydrocarbons – there is a double bond between 2 carbon atoms. General formula is CnH2n - twice as many hydrogen atoms as carbon atoms Ethene – C2H4 Propene – C3H6 Butene – C4H8 Testing for alkenes 23/05/2017 Orange bromine water Unsaturated alkene Colourless bromine water Making ethanol 23/05/2017 1) Ethene reacted with steam in presence of catalyst. Ethene comes from crude oil – will eventually run out 2) Sugar fermented with yeast. Carbon dioxide also produced. Sugar grown - renewable Monomers and Polymers 23/05/2017 Alkenes can be used to make polymers (plastics) Lots of small alkene molecules – monomers – are joined together to make very large molecules – polymers Ethene poly(ethene) Propene poly(propene) n C C C C n Ethene Poly(ethene) Properties & uses of polymers 23/05/2017 • • • • Light and stretchy – used for plastic bags Elastic – used to make Lycra Waterproof – fabric coating Non-biodegradable – don’t rot Extracting plant oils • Extracted from fruits and seeds • Plant material is crushed, pressed and filtered to remove impurities 23/05/2017 Emulsions 23/05/2017 Emulsions are a mixture of oil and water. Droplets of one liquid are suspended in the other liquid. Emulsions are thicker and have lots of uses – mayonnaise, ice cream and paint are examples Emulsifiers stop emulsions from separating – e.g. egg yolk Emulsifiers - HT 23/05/2017 Emulsifiers have a hydrophilic (likes water, hates oil) part emulsifier water hydrophobic (likes oil, hates water) part. oil Saturated and unsaturated oils 23/05/2017 Vegetable oils are unsaturated. They have a carbon-carbon double bond. Tested for bromine water Hydrogenating oil- HT 23/05/2017 Unsaturated vegetable oil can be hardened by reacting them with hydrogen in the presence of a nickel catalyst at 60oC. Hydrogen adds to the carbon-carbon double bond. Hydrogenated oils have higher melting points = solid at room temperature. Useful for cakes and pastries The Structure of the Earth 23/05/2017 Thin crust - 10-100km thick Mantle – has properties of a solid but it can also flow Core – made of molten nickel and iron. Outer part is liquid and inner part is solid Tectonic plates 23/05/2017 The Earth’s crust is split up into tectonic plates: These plates are moving apart from each other a few centimetres every year due to convection currents in the mantle caused by the radioactive decay of rocks inside the core. Tectonic theory 23/05/2017 It was once thought that the oceans and the continents were formed by shrinkage from when the Earth cooled down after being formed. Alfred Wegener proposed that there was once a single land mass, that has changed as tectonic plates moved - TECTONIC THEORY. The evidence he had was the continents look like they “fit” together. had similar rock patterns and fossil records. Tectonic theory 23/05/2017 Wegener couldn't explain how continental drift happened so nobody believed him The Answer: 1) Scientists discovered 50 years later that the Earth generates massive amounts of heat through radioactive decay in the core. This heat generated convection currents in the mantle causing the crust to move 2) We also now know that the sea floor is spreading outwards from plate boundaries Movement at boundaries 23/05/2017 Movement of plate boundaries can be sudden and disastrous. Earthquakes and volcanoes happen at the boundaries between tectonic plates 23/05/2017 Evolution of the Earth’s Atmosphere Carbon Methane Ammonia dioxide Phase 1 – volcanoes give out CO2, H2O, CH4 & NH4. Water vapour and carbon dioxide condensed to form oceans 4 Billion years 3 Billion years Oxygen 2 Billion years Nitrogen Others Present day atmosphere = 78% N, 21% O2, 1% noble gases and about 0.03% CO2 1 Billion years Phase 2 – green plants evolved, using up CO2 and producing O2. Present day