C1 1.1 ATOMS, ELEMENTS & COMPOUNDS • All substances are made of atoms • Elements are made of only one type of.
Download ReportTranscript C1 1.1 ATOMS, ELEMENTS & COMPOUNDS • All substances are made of atoms • Elements are made of only one type of.
C1 1.1 ATOMS, ELEMENTS & COMPOUNDS • All substances are made of atoms • Elements are made of only one type of atom • Compounds contain more than one type of atom • Compounds are held together by bonds An atom is made up of a tiny nucleus with electrons around it • Each element has its own symbol in the periodic table • Columns are called GROUPS. • Elements in a group have similar properties • Rows are called PERIODS • The red staircase splits metals from non-metals C1 1.2 ATOMIC STRUCTURE • Atoms contain PROTONS, NEUTRONS & ELECTRONS • Protons and Neutrons are found in the NUCLEUS • Electrons orbit the nucleus PARTICLE RELATIVE CHARGE RELATIVE MASS Proton +1 (positive) 1 Neutron 0 (neutral) 1 Electron -1 (negative) 0 Any atom contains equal numbers of protons and electrons • ATOMIC NUMBER the number of protons in the nucleus the periodic table is arranged in this order • MASS NUMBER the number of protons plus neutrons Number of neutrons = Mass Number – Atomic Number C1 1.3 ELECTRON ARRANGEMENT • Electrons are arranged around the nucleus in SHELLS (or energy levels) • The shell closest to the nucleus has the lowest energy • Electrons occupy the lowest available energy level High energy shell This is how we draw atoms and their electrons Sodium Low energy shell • Atoms with the same number of electrons in the outer shell belong to the same GROUP in the periodic table • Number of outer electrons determine the way an element reacts • Atoms of the last group (noble gases) have stable arrangements and are unreactive C1 1.4 FORMING BONDS • Atoms can react to form compounds in a number of ways: i) Transferring electrons IONIC BONDING ii) Sharing electrons COVALENT BONDING IONIC BONDING COVALENT BONDING • • • • • • When 2 non-metals bond • Outermost electrons are shared • A pair of shared electrons forms a bond When a metal and non-metal react Metals form positive ions Non-metals from negative ions Opposite charges attract A giant lattice is formed CHEMICAL FORMULAE • Tells us the ratio of each element in the compound • In ionic compounds the charges must cancel out: E.g. MgCl2 We have 2 chloride ions for every magnesium ion C1 1.5 CHEMICAL EQUATIONS • Chemical equations show the reactants (what we start with) and the products (what we end up with) • We often use symbol equations to make life easier CaCO3 CaO + CO2 Ca = 1 C=1 O=3 Ca = 1 C=1 O=3 • This is balanced – same number of each type of atom on both sides of the equation • We can check this by counting the number of each type on either side MAKING EQUATIONS BALANCE Equations MUST balance We can ONLY add BIG numbers to the front of a substance We can tell elements within a compound by BIG letters CaCO3 this is a compound made of 3 elements (calcium, carbon and oxygen) H2 + O2 H2O H=2 O=2 H=2 O=1 Add a 2 to the products side to make the oxygen balance H2 + O2 2H2O H=2 O=2 H=4 O=2 This has changed the number of hydrogen atoms so we must now adjust the reactant side: 2H2 + O2 2H2O C1 2.1 LIMESTONE & ITS USES • Limestone is made mainly of Calcium Carbonate • Calcium carbonate has the chemical formulae CaCO3 • Some types of limestone (e.g. chalk) were formed from the remains of animals and plants that live millions of years ago USE IN BUILDING HEATING LIMESTONE We use limestone in many buildings by cutting it into blocks. Breaking down a chemical by heating is called THERMAL DECOMPOSITION Other ways limestone is used: Cement = powdered limestone + powdered clay Concrete = Cement + Sand + Water Calcium Calcium + Carbon Carbonate Oxide Dioxide CaCO3 CaO + CO2 ROTARY LIME KILN This is the furnace used to heat lots of calcium carbonate and turn it into calcium oxide Calcium oxide is used in the building and agricultural industries C1 2.2 REACTIONS OF CARBONATES • Buildings made from limestone suffer from damage by acid rain • This is because carbonates react with acid to form a salt, water and carbon dioxide Calcium + Hydrochloric Calcium + Water + Carbon Carbonate Acid Chloride Dioxide CaCO3 + 2HCl CaCl2 + H2O + CO2 TESTING FOR CO2 • We use limewater to test for CO2 • Limewater turns cloudy • A precipitate (tiny solid particles) of calcium carbonate forms causing the cloudiness! HEATING CARBONATES Metal carbonates decompose on heating to form the metal oxide and carbon dioxide MgCO3 MgO + CO2 C1 2.3 THE LIMESTONE REACTION CYCLE • Limestone is used widely as a building material • We can also use it to make other materials for the construction industry Calcium Carbonate + Heat Calcium Oxide Calcium Oxide + Water Calcium Hydroxide (Limewater) Step 4: Add CO2 Ca(OH)2 + CO2 CaCO3 + H2O Calcium Carbonate Limestone Step 1: Add Heat CaCO3 CaO + CO2 Calcium Oxide Calcium Hydroxide Solution Step 2: Add a bit of water Step 3: Add more water & filter Ca(OH0)2 + H2O Ca(OH)2 (aq) CaO + H2O Ca(OH)2 Calcium Hydroxide C1 2.4 CEMENT & CONCRETE CEMENT Made by heating limestone with clay in a kiln MORTAR Made by mixing cement and sand with water CONCRETE Made by mixing crushed rocks or stones (called aggregate), cement and sand with water C1 2.5 LIMESTONE ISSUES BENEFITS DRAWBACKS • Provide jobs • Destroys habitats • Lead to improved roads • Increased emissions • Filled in to make fishing lakes or for planting trees • Noisy & Dusty • Can be used as landfill sites when finished with • Dangerous areas for children • Busier roads • Ugly looking C1 3.1 EXTRACTING METALS • A metal compound within a rock is called an ORE • The metal is often combined with oxygen • Ores are mined from the ground and then purified Whether it’s worth extracting a particular metal depends on: How easy it is to extract How much metal the ore contains The reactivity series helps us decide the best way to extract a metal: Metals below carbon in the series can be reduced by carbon to give the metal element Metals more reactive than carbon cannot be extracted using carbon. Instead other methods like ELECTROLYSIS must be used THE REACTIVITY SERIES C1 3.2 IRON & STEELS • Iron Ore contains iron combined with oxygen • We use a blast furnace and carbon to extract it (as it’s less reactive than carbon) • Carbon REDUCES the iron oxide; Iron (III) Oxide + Carbon Iron + Carbon Dioxide • Iron from the blast furnace contains impurities: Makes it hard and brittle • A metal mixed with other elements is called an ALLOY Can be run into moulds to form cast iron Used in stoves & man-hole covers E.g. Steel Iron with carbon and/or other elements • Removing all the carbon impurities gives There are a number of types of steel alloys: us pure iron Soft and easily shaped Too soft for most uses Need to combine it with other elements Carbon steels Low-alloy steels High-alloy steels Stainless steels C1 3.3 ALUMINIUM & TITANIUM Aluminium Titanium Property • Shiny • Light • Low density • Conducts electricity and energy • Malleable – easily shaped • Ductile – drawn into cables and wires • Strong • Resistant to corrosion • High melting point – so can be used at high temperatures • Less dense than most metals Use • Drinks cans • Cooking foil • Saucepans • High-voltage electricity cables • Bicycles • Aeroplanes and space vehicles • High-performance aircraft • Racing bikes • Jet engines • Parts of nuclear reactors • Replacement hip joints Extraction Electrolysis Displacement & Electrolysis • Aluminium ore is mined and extracted. • Alumminium oxide (the ore) is melted • Electric current passed through at high temperature • Use sodium or potassium to displace titanium from its ore • Get sodium and magnesium from electrolysis Expensive process – need lots of heat and electricity Expensive – lots of steps involved, & needs lots of heat and electricity C1 3.4 EXTRACTING COPPER COPPER-RICH ORES LOW GRADE COPPER ORES These contain lots of copper. There are 2 ways to consider: These contain smaller amount of copper. There are 2 main ways: 1. Smelting 1. Phytomining • 80% of copper is produced this way • Heat copper ore strongly in a furnace with air Copper + Oxygen Copper + Sulphur Sulphide Dioxide • Then use electrolysis to purify the copper • Expensive as needs lots of heat and electricity 2. Copper Sulphate • Add sulphuric acid to a copper ore • Produces copper sulphate • Extract copper using electrolysis or displacement • Plants absorb copper ions from low-grade ore • Plants are burned • Copper ions dissolved by adding sulphuric acid • Use displacement or electrolysis to extract pure copper 2. Bioleaching • Bacteria feed on low-grade ore • These produce a waste product that contains copper ions • Use displacement or electrolysis to extract pure copper C1 3.5 USEFUL METALS TRANSITION METALS COPPER ALLOYS • Bronze – Copper + Tin - Tough - Resistant to corrosion Found in the central block of the periodic table Properties: • Good conductors of electricity and energy • Strong • Malleable – easily bent into shape Uses: • Buildings • Transport (cars, trains etc) • Heating systems • Electrical wiring Example: Copper 1. Water pipes – easily bent into shape, strong, doesn’t react with water 2. Wires – ductile and conduct electricity Brass – Copper + Zinc - Harder but workable ALUMINIUM ALLOYS • Alloyed with a wide range of other elements • All have very different properties • E.g. in aircraft or armour plating! GOLD ALLOYS • Usually add Copper to make jewellery last longer C1 3.6 METALLIC ISSUES EXPLOITING ORES BUILDING WITH METALS Mining has many environmental consequences: Benefits • Scar the landscape • Steel is strong for girders • Noisy & Dusty • Aluminium is corrosion resistant • Destroy animal habitats • Many are malleable • Large heaps of waste rock • Copper is a good conductor and not reactive • Make groundwater acidic • Release gases that cause acid rain RECYCLING METALS • Recycling aluminium saves 95% of the energy normally used to extract it! • This saves money! • Iron and steel are easily recycled. As they are magnetic they are easily separated • Copper can be recycled too – but it’s trickier as it’s often alloyed with other elements Drawbacks • Iron & steel can rust • Extraction causes pollution • Metals are more expensive than other materials like concrete C1 4.1 FUELS FROM CRUDE OIL CRUDE OIL • A mixture of lots of different compounds [A mixture is 2 or more elements or compounds that are not chemically bonded together] • We separate it into substances with similar boiling points • These are called fractions • This is done in a process called fractional distillation HYDROCARBONS Nearly all the compounds in crude oil are hydrocarbons Most of these are saturated hydrocarbons called alkanes Methane CH4 Ethane C2H6 Propane C3H8 General formula for an alkane is CnH(2n+2) Butane C4H10 C1 4.2 FRACTIONAL DISTILLATION This is the process by which crude oil is separated into fractions These are compounds with similar sized chains Process relies on the boiling points of these compounds The properties a fraction has depend on the size of their hydrocarbon chains SHORT CHAINS ARE: Very flammable Have low boiling points Highly volatile (tend to turn into gases) Have low viscosity (they flow easily) Long chains have the opposite of these! Crude oil fed in at the bottom Temperature decreases up the column Hydrocarbons with smaller chains found nearer the top C1 4.3 BURNING FUELS COMPLETE COMBUSTION POLLUTION Lighter fractions from crude oil make good fuels Fossil fuels also produce a number of impurities when they are burnt They release energy when they are oxidised burnt in oxygen: propane + oxygen carbon dioxide + water These have negative effects on the environment The main pollutants are summarised below Sulphur Dioxide Carbon Monoxide Nitrogen Oxide • Poisonous gas • Produced when not enough oxygen • Poisonous • It’s acidic • Causes acid rain • Causes engine corrosion • Poisonous gas • Prevents your blood carrying oxygen around your body • Trigger asthma attacks • Can cause acid rain Particulates • Tiny solid particles • Contain carbon and unburnt hydrocarbon • Carried in the air • Damage cells in our lungs • Cause cancer C1 4.4 CLEANER FUELS Burning fuels releases pollutants that spread throughout the atmosphere: GLOBAL WARMING GLOBAL DIMMING • Caused by carbon dioxide • Caused by particulates • Causing the average global temperature to increase • Reflect sunlight back into space • Not as much light gets through to the Earth SULPHUR DIOXIDE • Caused by impurities in the fuel CARBON MONOXIDE Formed by incomplete combustion • Affect asthma sufferers • Cause acid rain damages plants & buildings CATALYTIC CONVERTERS • Reduces the carbon monoxide and nitrogen oxide produced • They are expensive • They don’t reduce the amount of CO2 Carbon + Nitrogen Carbon + Nitrogen Monoxide Oxide Dioxide C1 4.5 ALTERNATIVE FUELS These are renewable fuels sources of energy that could replace fossil fuels (coal, oil & gas) + BIODIESEL ETHANOL HYDROGEN • Less harmful to animals • Easily made by fermenting sugar cane • Very clean – no CO2 • Gives off CO2 but the sugar cane it comes from absorbs CO2 when growing • Water is the only product • Large areas of farmland required • Less food produced as people use it for fuel instead! • Hydrogen is explosive • Takes up a large volume storage becomes an issue • Breaks down 5 × quicker • Reduces particulates • Making it produces other useful products •‘CO2 neutral’ – plants grown to create it absorb the same amount of CO2 generated when it’s burnt - • Large areas of farmland required • Less food produced Famine • Destruction of habitats • Freezes at low temps C1 5.1 CRACKING HYDROCARBONS CRACKING Breaking down large hydrocarbon chains into smaller, more useful ones CRACKING PROCESS SATURATED OR UNSATURATED? 1. Heat hydrocarbons to a high temp; then either: We can react products with bromine water to test for saturation: 2. Mix them with steam; OR 3. Pass the over a hot catalyst Positive Test: Unsaturated + Bromine COLOURLESS hydrocarbon Water EXAMPLE OF CRACKING Cracking is a thermal decomposition reaction: = ALKENES 800oC C10H22 Decane C5H12 + C3H6 + C2H4 Pentane Propene Ethene ALKENES • These are unsaturated hydrocarbons • They contain a double bond • Have the general formula CnH2n Negative Test: Saturated + Bromine NO RECTION Hydrocarbon Water (orange) = ALKANES C1 5.2 POLYMERS FROM ALKENES PLASTICS Are made from lots of monomers joined together to make a polymer MONOMERS POLYMER Poly(ethene) Ethene HOW DO MONOMERS JOIN TOGETHER? • • • Double bond between carbons ‘opens up’ Replaced by single bonds as thousands of monomers join up It is called POLYMERISATION Simplified way of writing it: n ‘n’ represent a large repeating number C1 5.3 NEW & USEFUL POLYMERS DESIGNER POLYMER Polymer made to do a specific job Examples of uses for them: • Dental fillings • Linings for false teeth • Packaging material • Implants that release drugs slowly SMART POLYMERS Have their properties changed by light, temperature or other changes in their surroundings Light-Sensitive Plasters Hydrogels Shape memory polymers • Top layer of plaster peeled back • Lower layer now exposed to light • Adhesive loses stickiness • Peels easily off the skin • Have cross-linking chains • Makes a matrix that traps water • Act as wound dressings • Let body heal in moist, sterile conditions • Good for burns • Wound is stitched loosely • Temperature of the body makes the thread tighten • Closes the wound up with the right amount of force C1 5.4 PLASTIC WASTE NON-BIODEGRADABLE RECYCLING • Don’t break down • Sort plastics into different types • Litter the streets and shores • Harm wildlife • Unsightly • Last 100’s of years • Melted down and made into new products • Fill up landfill sites • Saves energy and resources…BUT BIODEGRADABLE PLASTICS • Plastics that break down easily • Hard to transport and • Need to be sorted into specific types • Granules of cornstarch are built into the plastic DISADVANTAGES OF BIODEGRADABLE PLASTICS • Microorganisms in soil feed on cornstarch • Demand for food goes up • This breaks the plastic down • Farmers sell crops like corn to make plastics • Food prices go up less can afford it STARVATION • Animal habitats destroyed to make new farmland C1 5.5 ETHANOL There are 2 main ways to make ethanol 1) FERMENTATION 2) ETHENE Sugar from plants is broken down by enzymes in yeast Hydration reaction water is added Ethene + Steam Ethanol Sugar + Yeast Ethanol + Carbon Dioxide 80% of ethanol is made this way C2H4 + H2O C2H5OH + Uses renewable resources + Continuous process – lots made! + Produces no waste products -Takes longer to produce - CO2 is given off - Requires lots of heat and energy - Relies on a non-renewable resource USES FOR ETHANOL H H H-C-C-O H H H • Alcohol A molecule of ethanol • Antiseptic wipes • Perfume • Rocket Fuel • Solvents C1 6.1 EXTRACTING VEGETABLE OIL There are 2 ways to extract vegetable oils from plants: 1) PRESSING 2) DISTILLATION 1. 2. 3. 4. 5. 1. 2. 3. Farmers collect seeds from plants Seeds are crushed and pressed This extracts oil from them Impurities are removed Oil is processed to make it into a useful product FOOD AND FUEL Vegetable oils are important foods: • Provide important nutrients (e.g. vitamin E) • Contain lots of energy so can also be used as fuels • Unsaturated oils contain double bonds (C=C) they decolourise Bromine water Plants are put into water and boiled Oil and water evaporate together Oil is collected by condensing (cooling the gas vapours) Lavender oil is one oil extracted this way Food Energy (kJ) Veg Oil 3900 Sugar 1700 Meat 1100 Table for info only – don’t memorise it! C1 6.2 COOKING WITH VEGETABLE OILS COOKING IN OIL • • • • • • Food cooks quicker Outside becomes crispier Inside becomes softer Food absorbs some of the oil Higher energy content Too much is unhealthy Double bonds converted to single bonds HARDENING VEGETABLE OILS • Reacting vegetable oils with HYDROGEN hardens them increases melting points • Makes them solid at room temperature makes them into spreads! + • Double bonds converted to single bonds C=C C-C • Now called a HYDROGENATED OIL 60oC + Nickel catalyst • Reaction occurs at 60oC with a nickel catalyst C1 6.3 EVERYDAY EMULSIONS Oils do not dissolve in water EMULSION EXAMPLES Emulsion Where oil and water are dispersed (spread out) in each other 1. 2. 3. 4. 5. These often have special properties Mayonnaise Milk Ice cream Cosmetics – face cream, lipstick etc Paint EMULSIFIERS • Stop water and oil separating out into layers Emulsifier molecule • Emulsifiers have 2 parts that make them work: Oil droplet 1. Hydrophobic tail – is attracted to oil 2. Hydrophilic head – is attracted to water. It has a negative charge - Water C1 6.4 FOOD ISSUES FOOD ADDITIVES VEG OILS Substance added to food to: Unsaturated Fats: • • • • • • • • Preserve it Improve its taste Improve its texture Improve its appearance Source of nutrients like vitamin E Keep arteries clear Reduce heart disease Lower cholesterol levels ANIMAL FATS Saturated Fats: E NUMBER Additives approved for use in Europe • Are not good for us • Increase risk of heart disease • Increase cholesterol EMULSIFIERS • Improve texture and taste of foods containing fats and oils • Makes them more palatable (tasty) and tempting to eat! E.g. chocolate! C1 7.1 STRUCTURE OF THE EARTH Atmosphere: Crust: Most lies within 10km of the surface Solid Rest is within 100km but it’s hard to judge! 6km beneath oceans 35km beneath land Core: Made of nickel and iron Mantle Outer core is liquid Behaves like a solid Inner core is solid Can flow very slowly Radius is 3500km Is about 3000km deep! C1 7.2 THE RESTLESS EARTH MOVING CONTINENTS The Earth’s crust and upper mantle are cracked into a number of pieces TECTONIC PLATES These are constantly moving - just very slowly Motion is caused by CONVECTION CURRENTS in the mantle, due to radioactive decay PANGAEA If you look at the continents they roughly fit together Scientists think they were once one large land mass called pangaea, which then broke off into smaller chunks PLATE BOUNDARIES Earthquakes and volcanoes happen when tectonic plates meet These are very difficult to predict C1 7.3 THE EARTH’S ATMOSPHERE IN THE PAST PHASE 1: Volcanoes = Steam & CO2 • Volcanoes kept erupting giving out Steam and CO2 • The early atmosphere was nearly all CO2 • The earth cooled and water vapour condensed to form the oceans PHASE 2: Green Plants, Bacteria & Algae = Oxygen • Green plants, bacteria and algae ran riot in the oceans! • Green plants steadily converted CO2 into O2 by the process of photosynthesis • Nitrogen released by denitrifying bacteria • Plants colonise the land. Oxygen levels steadily increase Like this for a billion years! PHASE 3: Ozone Layer = Animals & Us • The build up of O2 killed off early organisms - allowing evolution of complex organisms • The O2 created the Ozone layer (O3) which blocks harmful UV rays from the sun • Virtually no CO2 left C1 7.4 LIFE ON EARTH No one can be sure how life on Earth first started. There are many different theories: MILLER-UREY EXPERIMENT • Compounds for life on Earth came from reactions involving hydrocarbons (e.g. methane) and ammonia • The energy for this could have been provided by lightning OTHER THEORIES 1. Molecules for life (amino acids) came on meteorites from out of space 2. Actual living organisms themselves arrived on meteorites 3. Biological molecules were released from deep ocean vents The experiment completed by Miller and Urey C1 7.5 GASES IN THE ATMOSPHERE THE ATMOSPHERE TODAY: CARBON DIOXIDE: • Taken in by plants during photosynthesis • When plants and animals die carbon is transferred to rocks • Some forms fossil fuels which are released into the atmosphere when burnt The main gases in air can be separated out by fractional distillation. The main gases in the atmosphere today are: 1. 2. 3. 4. Nitrogen 78% Oxygen 21% Argon 0.9% Carbon Dioxide 0.04% These gases are useful in industry C1 7.6 CARBON DIOXIDE IN THE ATMOSPHERE The stages in the cycle are shown below: Carbon moves into and out of the atmosphere due to • Plants – photosynthesis & decay • Animals – respiration & decay • Oceans – store CO2 • Rocks – store CO2 and release it when burnt CO2 LEVELS Have increased in the atmosphere recently largely due to the amount of fossil fuels we now burn