Chemistry C1

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Atoms, Elements and The Periodic Table

  • An element is one type of atom
  • Elements are arranged in the periodic table
  • Each element has a symbol i.e C = carbon, Na = sodium
  • Groups (columns) tell you the number of electrons in an atom's outer shell
  • Periods (rows) tell you how many shells of electrons an atom has
  • Left side = metals, right side = non-metals
  • The Nobel Gases (group 8 or 0) have full outer shells so are stable and unreactive
  • Atoms are made up of protons, neutrons, and electrons
  • Protons and neutrons in the nucleus
  • Electrons arranged in shells around the nucleus
  • Number of protons = number of electrons
  • Relative masses: Proton = 1, Neutron = 1, Electron = almost 0
  • Relative charges: Proton = 1, Neutron = 0, Electron = -1
  • Charge of an atom is 0
  • Charge in the nucleus is positive
  • Atomic/Proton number (bottom number) is the number of protons in an element
  • Mass number (top number) is the sum of the protons and neutrons in an atom
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Chemical Reactions

  • Elements react to form compounds
  • Reacting involves giving, taking, or sharing electrons between reactants
  • When a metal and a non-metal react, ions are formed
    • Ions are atoms that are charged
    • During a reaction, the metal gives away electrons and so becomes positively charged as it now has more protons
    • The non-metal becomes negatively charged as it has more electrons
    • The opposite charges attracteach other to form compounds
    • This is called ionic bonding
  • When two non-metals react, they must share electrons
    • Sharing electrons is called covalent bonding
    • The product of a reaction that uses covalent bonding is a molecule
  • Reactions are represented by word, and (balanced) symbol equations
  • Mass of reactants = mass of products
    • No atoms are created or destroyed
    • This is the Law of Conservation of Mass
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  • Limestone can be used for building:
    • As bricks
    • To make cement: powdered limestone + powdered clay heated in a kiln
    • To make motar (sticks bricks together): cement + sand + water
    • To make concrete: cement + sand + aggregate (water and gravel
  • Advantages of quarring limestone
    • Provides job and brings money into local economy which can lead to local improvements
    • Widely available, cheaper than granite or marble, hard-wearing looks attractive
    • Provides things that people want i.e houses
    • Can be used as a nuetraliser for soil and chimney
    • Limestone and its products don't rot, are easy to cut, and fire resistant
  • Disadvantages of quarrying limestone
    • Dust, noise and visual pollution
    • Destroys habitats
    • Waste materials make tip
    • Transportation causes noise and air pollution
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Calcium Carbonate

  • Limestone is mostly made of calcium carbonate
  • Calcium carbonate can be thermally decomposed (broken down by heat) to make calcium oxide and carbon dioxide
  • Other carbonates such as copper, zinc, and sodium etc. can be decomposed in a similar way but not always at a temperature that canbe reached by a bunsen burner
  • Calcium oxide can react with water to produce calcium hydroxide
  • A solution of calcium hydroxide in water is known as limewater
    • Limewater is used as the test for carbon dioxide
    • If carbon dioxide is present, the solution turns cloudy due to the formation of an insoluable precipitate of calcium carbonate
  • All carbonates react with acids to produce carbon dioxide, a salt, and water
  • Limestone is damaged by acid rain (dilute sulfuric or nitric acid)
    • The calcium carbonate reacts with the acid to form a salt, water and carbon dioxide
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Extracting Metals: Impacts

  • Metals are made from ores which are rocks that contain enough metal to make it worthwhile to extract the metal from it. This is usually an oxide of the metal
  • Advantages of extracting metals
    • It results in useful products
    • Creates jobs
    • Brings money into the local economy, therefore things such as healthcare and infrastructure can be improved
  • Disadvantages of extracting metals
    • Bad for the environment
    • Noise pollution
    • Visual pollution
    • Transportation causes pollution and traffic
    • Destroys habitats
    • Mine shafts can be dangerous once abandoned
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Extracting Metals: How

  • Metals are only extracted if it is economicall viable (worth the money)
    • This may change over time due to suppl and demand
  • Metals are extracted from their ores chemically by reduction, electrolysis or displacement
  • Reduction is removing oxygen from an ore, using carbon ie. iron (III) oxide + Carbon --> iron + carbon dioxide
  • Only metals lower than carbon in the Reactivity Series can be extracted by reduction as it can only take oxygen away from metal less reactive than itself
  •  Metals more reactive than carbon are extracted from molten compounds using electrolysis
  • This process is a lot more expensive as it requires more energy and is a longer process
  • Displacement is swapping places
  • More reactive metals react more vigourouslso putting a reactive metal into a solution of a dissolved metal compound will make the reactive metal replace the less reactive metal in the compound. The more reactive metal makes stronger bonds to the non-metal and pushes out the less reactive metal ie. copper sulfate + iron --> iron sulfate + copper
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  • Copper is extracted by reduction: heating in a furnace (smelting) but it is impure so doesn't conduct electricty well. It is purified by electrolysis to make it a better conductor
  • Electrolysis of copper
    • Electrolysis requires a liquid with free electrons to conduct electricity - electrolyte (Metal salt solutions (ie. copper sulfate) or molten metal oxides)
    • Electrons are taken away by the +ve anode and given to the -ve cathode
    • Cu2+ ions go into the solution
    • At the cathode, ions gain electrons, turn back into copper atoms and bond to the electrode
    • Impurites are dropped at the anode as sludge
  • Copper rich ores are limited and demand is growing. We need new ways of extracting copper
  • Bioleaching: bacteria separate copper from copper sulfide, getting their engery from the bond. The solution left produced during the process (leachate) contains copper that can be extracted.
  • Phytomining: plants are grown in copper soil. The copper cannot be used by the plant so it colects in the leaves. The plant is dried and burnt so the copper can be collected from ash.
  • These new methods are less damaging to the environment, but they are slow
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The Importance of Recycling

  • Extracting metals takes a lot of energy that mostly comes from fossil fuels
  • Fossil fuels are running put so we need to conserve them
  • Also, burning fossil fuels contributes to acid rain, climate change, and global dimming
  • Recycling metals only ises a small fraction of the energy that would be needed to extract them
  • Energy is expensive so therefore recycling saves money
  • There is a finite amount of each metal in the Earth so we need to conserve resources
  • Recycling metals reduce the amount of rubbish that goes to landfill
    • Landfill takes up space and pollutes the surroundings
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Properties of Metals

  • The general properties of all metals are strong, malleable and conduct heat and electricity well
  • Copper's specific properties that make it good for making wires and plumbing pipes
    • Good electrical conductor, Hard and strong but can be ben, Doesn't react with water
  • Aluminium's specific properties that make it good for making aeroplanes
    • Corrosion resistant, Low densit, Forms hard and strong alloys
  • Titanium's specifc properties that make it good for making hip replacements
    • Low density, Very stron, Corrosion resistant
  • Metals are good structure materials but not perfect
    • Some corrode when exposed to air or water, making them weaker
    • Metals can get tired when stress is put on then repeatedly (metal fatigue), ie. in planes, which can make them dangerous as they may break
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  • Iron straight out of a blast furnace is 96% iron and 4% carbon. The impurites make the cast iron brittle so it's only used for ornamental railings etc.
  • When impurities are removed, the iron has uniform arrangement of identicle atoms
  • This allows the layers to slide over each other, making it easy to shape, but too bendy so most iron is made into the alloy steel
  • Low carbon steel is 0.1% carbon, easily shaped and therefore used in car bodies
  • High carbon steel is 1.5% carbon, very hard and inflexible, and used for bridges and blades
  • Stainless steel has chromium or maybe nickel added, it's corrosion resistant and so is used for cutlery or containers for corrosive materials
  • Different elements have different sized atoms, so when mixed together, the different sizes upset the uniform arrangement of the metal so it is harder for layers to slide over each other, making the alloy harder than pure metal
  • Alloys used to be made by trail and error but now they are made for specific.uses
  • Bronze = copper + tin: used for statues and medals
  • Cupronickel = copper + nickel: hard and corrosion resistant, used for silver coins
  • Gold alloys used to harden gold jewellery
  • Aluminium alloys used to make aeroplanes as it is low density and strong
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Crude Oil

  • Crude oil is a mixture of different types of hydrocarbon (different length molecules of C and H)
  • Each kind of fuel can be separated by fractional distillation in a fractioning column
    • The oil is heated and enters the column at the bottom.
    • The evaporated hydrocarbons rise up the column
    • Further up in the column, the temperature decreases, causing condensation
    • The different hydrocarbons condense at different point so are separated into fractions
  • Each fraction of fuel is made up of similar length molecules called alkanes
  • The fractions follow trends in their properties
    • The shorter the molecule, the less viscous (gloopy) it is
    • The shorter the molecule, the lower the boiling point - more volatile
    • The shorter the molecule, the more flammable the hydrocarbon is
  • The first 4 alkanes are methane (CH4), Ethane (C2H6), Propane (C3H8) and Butane (C4H10)
  • The general formula for alkanes is CnH(2n+2)
  • Carbon atoms can form 4 bonds and hydrogen can form 1 bond
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Using Crude Oil as a Fuel

  • The uses of a hydrocarbon depends on it's properties
    • Volatile fuels (refinery gas) are gas at room temperature so can be used as bottled gas
    • Petrol is liquid at room tempurature and is runny so it flows through a car engine
    • Viscous hydrocarbons are thick so are good for lubricating engine parts
  • Advantages of crude oil
    • Crude oil fractions burn cleanly so they make good fuels
    • Crude oil provides the raw materials for making different chemicals and plastics
    • At the moment, crude oil is reliable, cheaper and easier to use than renewable sources
  • Disadvantages of crude oil
    • It is non renewable
    • We should use more renewable energy (ie. solar and wind) for generating electricty
    • Crude oil can result in oil spills which can poison and kill animals
    • To release energy from the oild, it must be burnt which contributes to global warming, acid rain and global dimming
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Environmental Problems

  • Burning fossil fuels to create electricity, oxidises the hydrogen and carbon in the hydrocarbon to produce carbon dioxide and water vapour
  • If the fuel contains sulfur impurites, they're oxidised to form sulfur dioxide
  • Oxides of nitrogen form when fuels are burnt at high temperatures
  • If there is not enough oxygen, partial combustion occurs so solid particles (soot) and unburnt fuel are release, poisonous carbon monoxide is produced
  • Sulfur dioxide and oxides of nitrogen cause acid rain
    • The gase mixes with the clouds to form dilute sulfuric or nitric acid which falls as acid rain
    • Acid rain damages limestone, makes lakes acid which can kill plants and animals
    • Links between acid rain and human health problems have been suggested
  • Removing sulfur from fuels before combustion will reduce sulfur emissions can reduce acid rain
  • This costs more, and uses more energy so more fossil fuels are burnt, releasing carbon dioxide
  • Petrol and diesel are starting to be replaced by low-sulfur versions
  • Power stations use Acid Gas Scrubbers to take harmful gases out before releasing fumes
  • We can also reduce acid rain by reducing our use of fossil fuels
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More Environmental Problems

  • The level of carbon dioxide in the atmosphere is increasing due to burning fossil fuels
  • Carbon dioxide has increased the average temperature of the Earth - global warming
  • This is a type of climate change that causes other changes ie. change in rainfall patterns etc
  • Paricles of soot and ash from when fossil fuels are burnt reflect sunlight back into space, and create more clouds, so there is less sunlight on Earth - global dimming (Many scientists don't believe this is real and blame inaccurate recording equipment)
  • Alternative fuels are being developed; they are mostly renewable
  • Ethanol: biofuel made from fermenting plant material; mixed with petrol to make it a better fuel. Good because it is carbon neutral however, car engines must be converted in order for it to work; also, ethanol isn't widely available so if farmers grow fuel crops rather than food crops, fod prices will rise
  • Biodiesel: biofuel made from vegetable oils (ie rapeseed or soybean), mixed with diesel so it can run on in a diesel engine. Good as it is carbon neutral and engines don't need to be converted, also, less sulfur dioxide is produced, but, we can't make enough to replace diesel
  • Hydrogen gas: released by the electolysis of water. Good becuase it is very clean, however, expensive engines are needed, and energy is used to release hydrogen
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Getting Stuff From Crude Oil

  • Long hydrocarbon chains can be cracked (thermally decomposed) into smaller chains
    • The long chain is heated to a vapour which is then passed over powered catalyst (aluminium oxide) at a high temperature (400-700*C)
    • The long chain is split on the surface of the catalyst
    • Most products of cracking are alkanes and unsaturated hydrocarbons called alkenes
  • Alkenes are hydrocarbons that have a double bond between the 2 carbons
  • The first 2 alkenes are ethene (C2H4) and propene (C3H6)
  • The general equation for the formula of an alkene is CnH2n
  • The alkene is adding bromine water to a substance - alkenes will decolourise the bromine water from orange to colourless becsaue the double bond has opened up and formed bonds with the bromine
  • Ethene can be hydrated with steam, in the presence of a catalyst to make ethanol
  • It's good as it is fairly cheap and not much is wasted but ethene is made from crude oil
  • Ethanol can be created from renewable sources by fermenting sugar with yeast: sugar --> carbon dioxide + ethanol
  • Good becuase sugar is a major crop, it makes a cheap fuel but the ethanol isn't concentrated so needs to be distilled and purified
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Making Polymers

  • Alkenes are used to make polymers by polymerisation - joining together small alkenes molecules (monomers) to form large molecules
    • Ie. lots of ethene molecules are joined together to make poly(ethene)
  • The properties of a polymer depends on what it's made from and how it is made
    • Ie. poly(ethene) made at 200*C and at 2000 atmospheres: flexible and low density
    • Poly(ethene) made at 60*C, a few atmospheres of pressure and a catalyst: dense and rigid
  • Different properties makes them good for different uses
    • Low density poly(ethene) is light and stretchy for making plastic bags
    • New uses for polymers are developed all the time ie. memory foam, dental polymers etc
  • Most polymers aren't biodegradable so it is hard to get rid of them
  • You should recycle and reuse polymers
  • Polymers are usually cheaper than things made of metal but they are made from crude oil
    • As the crude oil is used up, crude oil prices, and its products such as polymers will get more expensive
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Plant Oils

  • Some fruits and seeds contain a lot of oil (ie. olives) that can be extracted and used for food and fuel.
  • To extract the oil, plant material is crushed, then pressed between metal plates to squash the oil out. The oil is separated from the crushed plants sing a centrifuge - like a spin dryer
  • Solvents can be used to get oil from the plant material
  • Distillation refines the oil and removes water, solvents and impurites
  • Vegetable oils are high in energy, contain nutrients (ie. vitamin E) and essential fatty acids
    • Vegetable oils have a higher boiling point than water so it can reach higher temperatures, this means it can cook food at higher temperatures and faster
    • Cooking with vegetable oil gives the food a different flavour because of the oil's own flavour, but also as many flavours come from chemicals that are soluable in oil
    • The oil carries the flavour, making it seem more intense
    • Using oil to cook food increases the energy
  • Vegetable oils, such as rapeseed or soybean oils, can be processed and turned to fuels
  • Biodiesel is very useful becuase it is very similar to normal diesel so engines do not need to be converted
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More Plant Oils

  • Oils and fats are either saturated or unsaturated
  • Monounsaturated fats contain one double bond
  • Polyunsaturated fats contain more than one double bond
  • Unsaturated fats are liquid at room temperature but can be hardened by hydrogenation
    • Reacting the fat with hydrogen in the presence of a nickel catalyst at 60*C
    • The hydrogen reacts with the double bonded carbons and opens the double bonds
    • Hydrogenated oils are solid at room temperature so are good as spreads on toast
    • Margarine is partially hydrogenated vegetable oil because if all bonds were single, the margarine would be too hard to spread
    • Partially hydrogenated oils are used instead of butter in processed food as it is cheaper and keeps longer
    • Partially hydrogenating oils means there are a lot of trans fats which are very bad
  • Vegetable oils are usually unsaturated, animal fats are usually saturated
  • Saturated fats are less heathly becuase they increase cholesterol
  • Natural unsaturated fats decrease cholesterol
  • Trans fats mean partially hydrogenated oils increase cholesterol which increases risk of heart disease
  • Cooking food in oil makes it more fattening
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  • Oils don't dissolve in water so when they are mixed, you have droplets of one suspended in the other - An emulsion
  • Emulsions are thicker than either water and oil; the more oil, the thicker the emulsion
  • Emulsion have lots of food uses such as mayonaise, but is also used in paint or creams etc.
  • Water and oil will eventually, naturally separate out so emulsifiers can be used to keep the emulsion mixed for longer
  • Emulsifier molecules have a hydrophilic head and a hydrophobic tail
    • The hydrophilic head attaches to the water but repels the oil
    • The hydrophobic tail attaches to the oil but repels the water
  • Each droplet in the mixture is surrounded by emulsifier molecules so the droplets cannot join together, causing the mixture to separate
  • Emulsifiers are good as it gives products longer shelf life; they also help companies produce food that is lower in fat but still have a good texture
  • However, some people are allergic to emulsifiers such as egg yolk
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Plate Tectonics

  • Alfred Wegener noticed similar fossils on different continents. Others had noticed this and people thought there were once land bridges which had now sunk under the sea
  • Wegener also noticed the continents fit like a jigsaw so he thought that there was once one continent that had split
    • Evidence included matching rock layers on different continents and fossils being found in the wrong places (ie. tropical plants found on Arctic islands)
    • He published his theory of continental drift in 1915
      • 300 million years ago there was one super continent called Pangaea
  • Wegener'sntheory was not accepted for many years as he had no explanation of the way the continents were drifting - he thought they were ploughing through the sea bed and were caused by tidal forces and the Earth rotation
  • Wegener also had inaccurate data so his calculations at the speed of the drifting was wrong
  • Wegener was also not believed becuase he wasn't a geologist
  • In the 1950s scientists could investigate the ocean floor and they found new evidence to support Wegener's theory. He wasn't completely right but he got the main idea
  • By the 1960s geologist were convinced and now we know the Earth's crust is made up of tectonic plates
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The Structure of the Eath

  • Crust: thin, cool layer we live on which is between 5-50km thick
  • Mantle: very gloopy substance which has the properties of a solid except that it can flow slowly
    • Radioactive decay occurs which produces a lot of heat which cause convection currents 
  • Core: solid core made of iron and nickel
  • The Earth has tectonic plates that float on the mantle
    • The convection currents cause the plates to drift a few cm per year
  • Sudden movements of plates can cause earthquakes
  • Volcanoes and earthquakes often occur at plate boundaries and are hard to predict
    • Impossible to predict movements as they happen suddenly
    • Scientists can predict when they are likely, not exactly when they'll occur
    • Some clues about volcanic eruptions are bulging ground and mini earthquakes
    • Some times mini earthquakes are a false alarm
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Evolution of the Atmosphere

  • Phase One
    • Earth was molten so atmosphere boiled away, when things cooled, the crust formed but volcanoes kept erupting which gave out lots of carbon dioxide
    • The early atmosphere was probably mostly carbon dioxide, water vapour, and a little bit of methane and ammonia
    • Oceans formed when water vapour condensed
  • Phase Two
    • Green plants and algae evolved
    • Carbon dioxide is dissolved into oceans or absorbed by plants which produce O2
    • Carbon locked up in dead plants and animals that will be released when burnt
  • Phase Three
    • Oxygen killed off some early organisms allowing complex animals to evolve
    • Oxygen created the ozone layer that blocks UV rays
    • There is virually no carbon dioxide left in the air now
    • Today's atmosphere is roughly 78% nitrogen, 21% oxygen, and 1% other gases
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Life, Resources and Atmospheric Change

  • Primordial soup is a theory of how life formed
    • Lightning struck, causing a chemical reaction between the gases in the early atmosphere (nitrogen, hydrgen, ammonia, and methane) resulting in formation of amino acids
    • Amino acids (that combined to form organic matter that evolved into life) were collected in a primordial soup out of which life eventually crawled
    • In the 1950s Miller and Urey did an experiment to prove the theory
    • They sealed the gases in their apparatus, heated them and applies an electrical charge for a week. They found amino acids were made - not as many as on Earth but along the right lines
  • The Earth has all the resources humans need.
  • You can fractionally distill air to get different products (method the same as for crude oil)
  • Increase Carbon dioxide levels affect the climate and oceans
    • Oceans store carbon dioxide but the amount being absorbed from the atmosphere is making them acidic which is bad for coral and animals, also, oceans won't be able to absorb more in the future
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