Presentation on theme: "C1.1 The Early atmosphere The first gases came from the eruption of Volcanoes and formed the Earth’s early atmosphere. The main gases in the early atmosphere."— Presentation transcript:
1 C1.1 The Early atmosphereThe first gases came from the eruption of Volcanoes and formed the Earth’s early atmosphere.The main gases in the early atmosphere were:Lots of carbon dioxideSome nitrogenLittle or no oxygenWater vapourAmmoniaVolcanoes release these gases today (and so scientists think the same processes operated in the past).The oceans were formed from the condensation of the water vapour to make liquid water.
2 C1.2 a changing atmosphere. Carbon dioxide levels fellOxygen levels roseCarbon dioxide fell because:Some carbon dioxide dissolved into the oceans.Some was absorbed by marine creatures who stored it tin their shells as calcium carbonate which later formed carbonate rocks.As the number of plants increased, the oxygen levels rose through photosynthesis. These plants absorb carbon dioxide too.A simple carbon cycleThe level of carbon dioxide in the atmosphere is maintained by several processes, photosynthesis, respiration and combustionGreen plants remove carbon dioxide from the atmosphere by photosynthesis. Respiration and combustion both release carbon dioxide into the atmosphere.These processes form a carbon cycle in which the proportion of carbon dioxide in the atmosphere remains about the same.
3 C1.4 The atmosphere today. Our atmosphere today… Changes in the atmosphere occur through;Natural activities:Volcanic activity can lead to a rise in sulphur dioxide; lightening can lead to a rise in nitrogen oxides.Human activity:burning fossil fuels can lead to an increase of carbon dioxide, carbon monoxide and sulphur dioxide.Deforestation lead to an increase in carbon dioxide; burning trees releases carbon dioxide (combustion), fewer trees to photosynthesise and absorb carbon dioxide; engines and furnaces release nitrogen oxides.Farming: increasing numbers of cattle and rice fields can lead to an increase of methane.Our atmosphere today…GasFormula% in dry airNitrogenN278OxygenO221ArgonAr0.9Carbon DioxideCO20.04othertraceHow do scientists use rocks to work out the composition of the Earth’s early atmosphere?Analyse the minerals in them and look for oxides. As more oxygen was present, more oxide mineralswere formed.
4 C1.5 Rocks and their Formation metamorphic – A rock changed by pressure and heat.sedimentary – A rock formed by the deposition of sediments.thermal decomposition – The breakdown of a compound into simpler substances by heating.electrolysis – The use of electricity to split a compound.granite – A type of igneous rock that is harder than limestone and marble.igneous – A rock formed from cooled magna.limestone – A type of sedimentary rock containing calcium carbonate.limewater – A limestone product made by fully dissolving quicklime in water. It is used to test for carbon dioxide.marble – A type of metamorphic rock that is harder than limestone but softer than graniteIgneous RocksExample – granite.Formed by the solidification of magma or lavaThey contain crystals whose size depends on the rate of cooling.Quick cooling = small crystalsFast cooling = large crystalsLimestone, chalk and marble are all forms of calcium carbonate and exist in the Earths crust.Metamorphic RocksExample – marbleFormed when heat or pressure is applied to other rocks.Marble is formed from chalk or limestone being heated and pressurised.Sedimentary rocksSedimentary rocks contain fossilsThey are formed from compaction of layers of rock over a long time.They are not as strong as other rocks so erode easily.Examples - chalk and limestone
5 C1.6 Limestone Limestone is made of calcium carbonate (CaCO3) The advantages and disadvantages of quarrying.C1.6 LimestoneLimestone is made of calcium carbonate (CaCO3)It is used in:Building materials- glass, cement, concreteImproving the pH of acid soilThermal Decomposition of Calcium CarbonateWhen metal carbonates are heated they break down into a metal oxide and carbon dioxide is given offCopper carbonate copper oxide + carbon dioxideCaCO CaO CO2Limestone is heated with clay to make cementCement is added to sand and water to make mortarCement is added to sand, aggregate and water to make concreteAdvantage of quarrying…jobs and valuable building resources.Problems associated with quarrying:Economic - moneySocial – the peopleEnvironmental - pollution
6 C1.7 Thermal decomposition Breaking down with heatEase of thermal decomposition of metal carbonates:Most difficult to decompose is sodium carbonate (10000C), calcium carbonate (8250C), zinc carbonate (3000C) and copper carbonate (2000C).Copper carbonate will start to decompose to form carbon dioxide and copper oxide. The reaction will absorb some of the heat from the fire. The carbon dioxide can help to put out the fire by reducing the amount of oxygen available for combustion.The mass of reactants do not change, the particles just get rearranged.The atoms take part in a chemical reaction they are very small.When calcium hydroxide is dissolved in water it makes Limewater.Copper carbonate copper oxide + carbon dioxideCaCO3(s) CaO(s) + CO2(g)Copper carbonate copper oxide + carbon dioxideZinc carbonate zinc oxide + carbon dioxide
7 C1.8 Chemical reactionsWord equations A word equation gives the names of the substances involved in a reaction. For example: copper + oxygen → copper(II) oxide Copper and oxygen are the reactants, and copper(II) oxide is the product.Precipitation reactions1) A simple example of conservation of mass is a precipitation reaction.2) Transition metals form coloured compounds with other elements. Many of these are soluble in water, forming coloured solutions. If sodium hydroxide solution is then added, a transition metal hydroxide is formed. These are insoluble. They do not dissolve but instead form solid precipitates. As all the reactants and products remain in the sealed reaction container then it is easy to show that the total mass is unchanged.copper sulfate + sodium hydroxide → copper hydroxide + sodium sulfateCuSO4 + 2NaOH → Cu(OH)2 + Na2SO4
8 C1.9 Reactions of Calcium Compounds KeywordsNeutralisation reaction - reaction in which a base or an alkali reacts with an acid.Limewater – Solution of calcium hydroxide. It is used to test for the presence of CO2 as it turns from colourless to cloudy.Making LimewaterHeating limestone - Calcium carbonate (CaCO3) turns it into Calcium oxide (CaO)CaCO3 (s) CaO(s) CO2 (g)Adding water to CaO – vigorous reaction that creates calcium hydroxide (crumbly solid)CaO(s) H2O (l) Ca(OH)2(s)Testing for CO2 - limewater turns cloudy/milky as calcium carbonate forms.Ca(OH)2(s) + CO2 (g) CaCO3 (s) H2O (l)NB – large quantities of CO2 will dissolve to form an acid. This reacts with the CaCO3 making it colourless again!Neutralising acids with limestoneCalcium compounds that neutralise acids:Calcium carbonate (CaCO3)Calcium oxide (CaO)Calcium hydroxide (Ca(OH)2)Uses of these alkalisFarmers neutralise soilPower stations use wet powdered CaCO3 to neutralise acidic waste gases like Sulfur dioxide and nitrous oxides. ( below is the equation for sulfur dioxide production)S (g) O(g) SO2 (g)
9 Acid + alkali → salt + water Hydrochloric acid is produced in the stomach to kill bacteria and to help digestion.1.10 indigestionIndigestion remedies contain substances to neutralise excess stomach acid.When an acidic compound dissolves in water it produces hydrogen ions, H+. These ions are responsible for the acidity of the solution.When an alkaline compound dissolves in water it produces hydroxide ions, OH−. These ions are responsible for the alkalinity of the solution.Acids react with alkalis to form salts. These are called neutralisation reactions. In each reaction, water is also formed:Acid + alkali → salt + waterExampleHydrochloric acid + sodium hydroxide → sodium chloride + waterHCl + NaOH → NaCl + H2OHydrochloric acid contains hydrogen ions and chloride ions dissolved in water.Sodium hydroxide solution contains sodium ions and hydroxide ions dissolved in water.Hydrochloric acid produces chloride salts e.g. calcium chlorideNitric acid produces nitrate salts e.g. calcium nitrateSulfuric acid produces sulfate salts e.g. calcium sulfate
10 C1.11NeutralisationYou need to be able to describe the reactions of hydrochloric acid and sulfuric acid with metal hydroxides, metal oxides and metal carbonates.Metal hydroxidesMetal hydroxides, such as sodium hydroxide, usually dissolve in water to form clear, colourless solutions. When an acid reacts with a metal hydroxide, the only products formed are a salt plus water. Here is the general word equation for the reaction:acid + metal hydroxide → a salt + waterthere is a temperature risethe pH of the reaction mixture changesMetal oxidesSome metal oxides, such as sodium oxide, dissolve in water to form clear, colourless solutions. Many of them are not soluble in water, but they will react with acids. Copper(II) oxide is like this. When an acid reacts with a metal oxide, the only products formed are a salt plus water. Here is the general word equation for the reaction:acid + metal oxide → a salt + waterMetal carbonatesAlthough sodium carbonate can dissolve in water, most metal carbonates are not soluble. Calcium carbonate (chalk, limestone and marble) is like this. When an acid reacts with a metal carbonate, the products formed are a salt plus water, but carbon dioxide is also formed. Here is the general word equation for the reaction:acid + metal carbonate → a salt + water + carbon dioxideYou usually observe bubbles of gas being given off during the reaction. You can show that the gas is carbon dioxide by bubbling it through
11 c1.13 electrolysis Electrolysis The process in which electrical energy from a d.c. supply decomposes compoundsThe process of electrolysisPositively charged ions move to the negative electrode during electrolysis. They receive electrons and are reduced.Negatively charged ions move to the positive electrode during electrolysis. They lose electrons and are oxidised.ELECTROLYSIS OF Hydrochloric AcidProduces chlorine at the positive electrodeProduces hydrogen at the negative electrode
12 C1.14 the importance of chlorine/Products from sodium chloride Learn all of this
13 1.15 Electrolysis of Water Water Produces oxygen at the positive electrodeProduces hydrogen at the negative electrodeIf the gas relights a glowing splint, it is oxygen.Electrolysis of SeawaterThis produces chlorine gas at the electrode.
14 1.16 ores C1.26 Acid rain Effects of acid rain Gold and platinum found naturally in the environment as they are unreactive.Most metals are found as ores (usually reacted with oxygen) in the Earths crust.Ores are rocks which contain metals.Extraction = getting the metal out of the rock. Sometimes you can…Heat the rock to get the metalOr use electrolysis.C1.26 Acid rainEffects of acid rainFish numbers started to decrease.Soils are made acid and can harm plants.Trees damagedErosion of buildings made of limestone.Causes of acid rain.Dissolved carbon dioxide and acidic gases in water.Sulphur dissolved in water from fossil fuels.Burning of fossil fuels which create sulphur.Uses of metals.Gold= jewelleryCopper = wiresSilver = jewellery
15 anode – The positive electrode used in electrolysis. cathode – The negative electrode used in electrolysis.electrolysis – The use of an electric current to separate out the elements in a compound.electrolyte – An ionic compound that conducts electricity when in a liquid state.ore – A rock that contains a metal combined with other elements in concentrations that make it profitable to mine.C1.17 Extracting metalIron is heated with carbon in a reduction reaction to extract it from its ore.Iron oxide + carbon iron + carbon dioxideAluminium is extracted from its ore by electrolysis because it is more reactive.Aluminium oxide aluminium + oxygenFactors which affect how a metal is extracted are cost and position in the reactivity series
16 C1.18 Oxidation and reduction Keywords Reduction – occurs when oxygen is removed from a compound Corrosion – when a metal is converted to its oxide by the action of moist air Oxidation – occurs when oxygen is added to an element or compound Rusting – the corrosion of ironMetal extraction is reductionMost metal ores are ‘oxides’To get the metal we must remove the oxygenWe say the compound has been reduced. It is a REDUCTION reactionExample 1 = Iron oxide is heated with CarbonIron oxide + Carbon Iron + Carbon dioxideExample 2 = Aluminium is obtained by electrolysis of aluminium oxideAluminium oxide Aluminium OxygenCorrosion of metals is oxidationMost metals corrodeSurface of a metal reacts with oxygen (or sometimes water)This is called OXIDATION reactionMore reactive metals corrode more rapidly (less reactive may not corrode at all e.g. Gold)A layer of metal oxide forms (this can stop further corrosion e.g. on Aluminium = and Al2O3 layer forms)
17 C1.19 Recycling metals Advantages Disadvantages KeywordsRecycled metal – when a used metal is melted down and made into something new.Many metals can be recycled…AdvantagesNatural reserves will last longerMost use less energy to recycle that to extract. E.g. Aluminium recycling 95% more energy efficient compared to extraction.Reduced mining which damages landscapes and causes pollution (dust and noise)Recycling produces less pollution. Examples supporting this areLead from its ore ‘galena’ produces sulfur dioxideCarbon dioxide is produced during extraction by electrolysis.DisadvantagesCosts money and uses energy to collect, sort and transport metals to be recycledThis can make it more expensive to recycle some metals the extract themThe most recycled metals in the UK are Lead , Iron and Aluminium and CopperMethodCollecting – requires people to be willing to separate their rubbishSeparating different metalsIron can be separated using a magnet (quick and easy)Others usually separated by hand (time consuming and labour intensive)Purifying – metals are melted down to form blocks
18 Aluminium Copper Gold Iron and Steel C1.20 Properties of metalsProperties include:– shiny when polished; conduct heat and electricity; malleable; ductile.KeywordsMalleable – can be hammered into shapeConduct – allows heat or electricity to pass through itDuctile – can be stretched into wiresDensity – the mass of a substance per unit volume; the unit is usually g/cm3AluminiumCopperGoldIron and SteelUseful PropertiesLow densityDoes not corrode (because of layer of oxide that forms quickly)UsesAeroplanes and cars to make them lighter (cheaper to run as they need less fuel)DuctileLow reactivity (does not react with water)Good electrical conductorElectrical cablesWater pipesVery unreactiveDoes not corrodeMalleableRemains shinyExcellent electrical conductorJewelleryElectronic devices (printed circuit boards and connection strips)Cheap to extract by heating with carbonPure iron too soft but in alloys is very usefulSteel (Iron mixed with carbon and other metals) is strong and hardMagneticUses (mainly as steel)Bridges, cars, cutlery, electrical goods, machinery, building frames, magnetic products
19 C1.21 Alloys Pure metal Alloys Keywords Alloy – a metal mixed with small amounts of other metals to improve their properties Carats – a measure of the purity of gold with pure gold being 24 carats Fineness – another measure of purity of gold (parts per thousand) Smart material – a material that’s properties change with a change in conditions Shape Memory Alloy – an alloy that can return to its original shape when heatedC1.21 AlloysPure metalPure metalAll atoms are the same size and therefore closely packed together.This means that layers of atoms slide over each other which makes the metal soft.In an alloy different atoms are added which prevent the atoms sliding so easily = harder and strongerAlloysExamples of AlloysAlloy steels – iron mixed with other metalsStronger that IronSome resist corrosion. Stainless steel NEVER corrodes (Iron with Chromium and Nickel)Gold - Pure gold (24 carat) too soft. 24 carat gold has a fineness of 1000 parts per thousandCopper and silver added to make it harderNitinol – Smart material made from nickel and titaniumReturn to original shape when heated.Used in repair of arteries (inserted in squashed and cold and warms with body to reshape)Flexible glasses frames
20 C1.22 Crude OilKey wordsHydrocarbons are compounds that contain carbon and hydrogen only.Crude oil is a complex mixture of hydrocarbons
21 C1.23 Crude Oil FractionsCrude oil is separated into simpler, more useful mixtures by fractional distillation.
22 There are 6 fractions you need to know… C1.23 Crude Oil FractionsThere are 6 fractions you need to know…FractionUsesGasesDomestic heating and cookingPetrolCar fuelKeroseneAircraft fuelDiesel oilFuel for some cars and trainsFuel oilFuel for ships and some power stationsBitumenSurfacing roads and roofs
23 C1.23 Crude Oil Fractions How do the fractions differ? Key words: Ignition – to set alightViscosity – How thick or runny a substance isHow do the fractions differ?FractionLength of moleculeEase of ignitionBoiling pointViscosityGasesShortLongEasyDifficultLowHighRunnyThick and stickyPetrolKeroseneDiesel oilFuel oilBitumen
24 C1.24 CombustionKey words: Combustion – a chemical reaction with oxygen (oxidation) to release energy. Complete combustion – where all the hydrocarbon is used up. Oxidation – the addition of oxygen.+ EnergyreleasedTested for using limewater. CO2 will turn it cloudy if present.Any hydrocarbon
25 C1.25 Incomplete Combustion Keywords:Incomplete combustion – where there is not enough oxygen for the fuel to completely burn.Carbon Monoxide – poisonous gas produced during incomplete combustion.Water is formed just like in complete combustion but there are not enough oxygen atoms to form CO2. Soot and Carbon Monoxide are formed instead.3 different equations show what can happen:Methane + Oxygen Carbon (soot) + WaterMethane + Oxygen Carbon Monoxide + WaterMethane + Oxygen Carbon Dioxide + Carbon Monoxide + Carbon (soot) + WaterDifferent percentages of CO2, CO and C are produced depending on the amount of oxygen present.
26 C1.25 Incomplete Combustion Problems of incomplete combustion:Carbon Monoxide is an odourless, colourless, toxic gas.It reduces the amount of oxygen carried by the Red Blood Cells.Carbon monoxide poisoning can kill.Soot can clog pipes carrying waste gases.Faulty or blocked boilers can produce carbon monoxide.
27 C1.26 Acid RainKey word:Acid rain – rain that is more acidic than normal.Impurities in hydrocarbons such as sulfur react with oxygen to produce sulfur dioxide. This dissolves in rainwater to form acid rain.4 Problems of Acid Rain:Rivers, lakes and soils become acidic harming living organismsDamages treesSpeeds up weathering of buildings made of limestone or marbleCorrodes metal
28 C1.27 Climate Change3 gases trap heat from the Sun and keep the Earth warm – Greenhouse EffectCarbon DioxideMethaneWater vapourThe Earths temperature varies.Human activity such as burning fossil fuels may influence this
29 C1.27 Climate ChangeThe amount of carbon dioxide in the atmosphere varies due to human activity – burning fossil fuels.How to reduce the amount of carbon dioxide in the atmosphere:Iron Seeding Oceans – Adding iron to the ocean encourages algal growth which photosynthesise and absorb carbon. They are eaten by other organisms which incorporate carbon into their shells which sinks to the bottom of the ocean.Converting carbon dioxide back to hydrocarbons – trapping gases from power stations and reacting them to make butane or propane to use as fuels.
30 C1.27 Climate Change Key words: Correlation – a pattern which is similar in two variables. It could be due to chance.Causation – when one variable causes the effect in the other.There is a correlation between carbon dioxide levels in the atmosphere and the Earths temperature.Not all scientists are convinced that increasing carbon dioxide levels cause global warning.Because…There are fluctuations throughout historyThere are other causes of global warningThere are other greenhouse gasesFuture predictions are just predictions
31 C1.28 BiofuelsKey words: Biofuel – A fuel made by humans from animal or plant material that has recently died. Ethanol – A fuel made from sugar beet or sugar cane. Biodiesel – Diesel made from plant material. Carbon neutral – a fuel that does not add any carbon to the atmosphere overall. Biofuels are a possible alternative to fossil fuels e.g. ethanol which could reduce demand for petrol.Advantages of BiofuelsDisadvantages of BiofuelsThey are renewableGrowing crops for fuels requires land that could be used to grow foodPlants remove carbon dioxide from the atmosphere as they growTransportation of the fuels produces carbon dioxideBurning the fuels produces carbon dioxide
32 C1.29 Choosing Fuels 4 factors that make a good fuel: How easily it burns.How much ash or smoke it produces.The comparative amount of heat energy it produces.How easy it is to store and transport.A fuel cell combines hydrogen and oxygen to make water and releases energy.Petrol, Kerosene and diesel oil are non-renewable fossil fuels made from crude oil.Methane is a non-renewable fossil fuel from natural gas.Advantages of using hydrogen as a fuelDisadvantages of using hydrogen as a fuelWhen hydrogen burns no carbon dioxide is produced, only water vapourHydrogen usually produced from natural gas and the process releases carbon dioxideHydrogen fuel cells are more efficient than petrol enginesHydrogen needs to be readily available firstRenewablePetrol stations would have to be converted to store and sell hydrogen tooCost of the above
33 Learn the formula and be able to draw each of these. C1.31 Alkanes and AlkenesAlkanes are saturated hydrocarbons which are present in crude oil.Learn the formula and be able to draw each of these.
34 Learn the formula and be able to draw each of these. C1.31 Alkanes and AlkenesAlkenes are unsaturated hydrocarbonsLearn the formula and be able to draw each of these.Bromine water is used to distinguish between alkanes and alkenesEthene bromine water colourless(colourless) (orange)Ethane bromine water orange
35 Know how to crack paraffin in the lab. Why is cracking needed? Crude oil has different amounts of each fraction. These don’t always match customer demand so they crack them to match demand.C1.32 CrackingCracking involves breaking down long saturated hydrocarbons (alkanes) into smaller useful ones. Some of these small molecules are unsaturated (alkenes).Know how to crack paraffin in the lab.
36 Learn the formula and equation C1.33 PolymerisationMany ethane molecules can combine in a polymerisation reaction.Learn the formula and equation
37 C1.33 Polymerisation4 examples of polymers you need to know…
38 C1.33 Polymerisation Polymer Properties Use Poly(ethane) – polythene Flexible, cheap, good insulatorPlastic bags, plastic bottles, cling film, insulation for electrical wiresPoly(propene) – polypropeneFlexible, shatterproof, high softening pointBuckets and bowlsPoly(chloroethene) - PVCTough, cheap, long-lasting, good insulatorWindow frames, gutters, pipes, insulation for electrical wiresPoly(tetrafluoroethene) PTFE or TeflonTough, slippery, resistant to corrosion, good insulatorNon stick coatings for saucepans, bearings for skis, containers for corrosive substances, stain proof coating for carpets, insulation for electrical wires
39 C1.34 Problems with Polymers Most are not biodegradable.They persist in landfill sites.They produce toxic gases when burned.How can we overcome these problems?Recycling polymers instead of landfill.Development of biodegradable polymers.