Understanding Atoms, Compounds & Elements: Essential Chemistry Concepts

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 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 Low energy shell Sodium • 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: • Transferring electrons  IONIC BONDING • Sharing electrons  COVALENT BONDING • IONIC BONDING • When a metal and non-metal react • Metals form positive ions • Non-metals from negative ions • Opposite charges attract • A giant lattice is formed • COVALENT BONDING • When 2 non-metals bond • Outermost electrons are shared • A pair of shared electrons forms a bond • 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 • 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 Ca = 1 C = 1 O = 3 Ca = 1 C = 1 O = 3 MAKING EQUATIONS BALANCEEquations 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 Add a 2 to the products side to make the oxygen balance H2 + O2 2H2O This has changed the number of hydrogen atoms so we must now adjust the reactant side: 2H2 + O2 2H2O H = 2 O = 2 H = 2 O = 1 H = 2 O = 2 H = 4 O = 2

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 We use limestone in many buildings by cutting it into blocks. Other ways limestone is used: Cement = powdered limestone + powdered clay Concrete = Cement + Sand + Water HEATING LIMESTONE Breaking down a chemical by heating is called THERMAL DECOMPOSITION 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) Calcium Carbonate Step 4: Add CO2 Ca(OH)2 + CO2 CaCO3 + H2O Step 1: Add Heat CaCO3 CaO + CO2 Limestone Calcium Oxide Calcium Hydroxide Solution Step 2: Add a bit of water CaO + H2O  Ca(OH)2 Step 3: Add more water & filter Ca(OH0)2 + H2O  Ca(OH)2 (aq) 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 • Provide jobs • Lead to improved roads • Filled in to make fishing lakes or for planting trees • Can be used as landfill sites when finished with • DRAWBACKS • Destroys habitats • Increased emissions • Noisy & Dusty • 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 • Can be run into moulds to form cast iron • Used in stoves & man-hole covers • Removing all the carbon impurities gives • us pure iron • Soft and easily shaped • Too soft for most uses • Need to combine it with other elements • A metal mixed with other elements is called an ALLOY • E.g. Steel  Iron with carbon and/or other elementsThere are a number of types of steel alloys: • Carbon steels • Low-alloy steels • High-alloy steels • Stainless steels

C1 3.3 ALUMINIUM & TITANIUM

C1 3.4 EXTRACTING COPPER • COPPER-RICH ORESThese contain lots of copper. There are 2 ways to consider:1.Smelting • 80% of copper is produced this way • Heat copper ore strongly in a furnace with air • Copper + Oxygen  Copper + SulphurSulphide 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 • LOW GRADE COPPER ORESThese contain smaller amount of copper. There are 2 main ways:1. Phytomining • 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 copper2. 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 • 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 • Water pipes – easily bent into shape, strong, doesn’t react with water • Wires – ductile and conduct electricity • COPPER ALLOYS • Bronze – Copper + Tin - Tough - Resistant to corrosion • 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 • Mining has many environmental consequences: • Scar the landscape • Noisy & Dusty • Destroy animal habitats • Large heaps of waste rock • 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 • BUILDING WITH METALS • Benefits • Steel is strong for girders • Aluminium is corrosion resistant • Many are malleable • Copper is a good conductor and not reactive • 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 General formula for an alkane is CnH(2n+2) Methane CH4 Ethane C2H6 Propane C3H8 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 Lighter fractions from crude oil make good fuels They release energy when they are oxidised burnt in oxygen: propane + oxygen  carbon dioxide + water POLLUTION Fossil fuels also produce a number of impurities when they are burnt These have negative effects on the environment The main pollutants are summarised below • Particulates • Tiny solid particles • Contain carbon and unburnt hydrocarbon • Carried in the air • Damage cells in our lungs • Cause cancer • Sulphur Dioxide • Poisonous gas • It’s acidic • Causes acid rain • Causes engine corrosion • Carbon Monoxide • Produced when not enough oxygen • Poisonous gas • Prevents your blood carrying oxygen around your body • Nitrogen Oxide • Poisonous • Trigger asthma attacks • Can cause acid rain

C1 4.4 CLEANER FUELS Burning fuels releases pollutants that spread throughout the atmosphere: • GLOBAL WARMING • Caused by carbon dioxide • Causing the average global temperature to increase • SULPHUR DIOXIDE • Caused by impurities in the fuel • Affect asthma sufferers • Cause acid rain  damages plants & buildings • GLOBAL DIMMING • Caused by particulates • Reflect sunlight back into space • Not as much light gets through to the Earth • CARBON MONOXIDE • Formed by incomplete combustion • CATALYTIC CONVERTERS • Reduces the carbon monoxide and nitrogen oxide produced • They are expensive • They don’t reduce the amount of CO2 Carbon + Nitrogen  Carbon + NitrogenMonoxide Oxide Dioxide

C1 4.5 ALTERNATIVE FUELS These are renewable fuels  sources of energy that could replace fossil fuels (coal, oil & gas)

C1 5.1 CRACKING HYDROCARBONS CRACKING Breaking down large hydrocarbon chains into smaller, more useful ones • CRACKING PROCESS • Heat hydrocarbons to a high temp; then either: • Mix them with steam; OR • Pass the over a hot catalyst SATURATED OR UNSATURATED? We can react products with bromine water to test for saturation: Positive Test: Unsaturated + Bromine  COLOURLESS hydrocarbon Water = ALKENES Negative Test: Saturated + Bromine  NO RECTION Hydrocarbon Water (orange) = ALKANES • EXAMPLE OF CRACKING • Cracking is a thermal decomposition reaction: • C10H22 C5H12 + C3H6 + C2H4 • ALKENES • These are unsaturated hydrocarbons • They contain a double bond • Have the general formula  CnH2n 800oC Decane Pentane Propene Ethene

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 ‘n’ represent a large repeating number Simplified way of writing it: n

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 • Top layer of plaster peeled back • Lower layer now exposed to light • Adhesive loses stickiness • Peels easily off the skin • Hydrogels • Have cross-linking chains • Makes a matrix that traps water • Act as wound dressings • Let body heal in moist, sterile conditions • Good for burns • Shape memory polymers • 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 • Don’t break down • Litter the streets and shores • Harm wildlife • RECYCLING • Sort plastics into different types • Melted down and made into new products • Saves energy and resources…BUT • Hard to transport and • Need to be sorted into specific types • DISADVANTAGES OF BIODEGRADABLE PLASTICS • Farmers sell crops like corn to make plastics • Demand for food goes up • Food prices go up  less can afford it  STARVATION • Animal habitats destroyed to make new farmland • Unsightly • Last 100’s of years • Fill up landfill sites • BIODEGRADABLE PLASTICS • Plastics that break down easily • Granules of cornstarch are built into the plastic • Microorganisms in soil feed on cornstarch • This breaks the plastic down

H H H-C-C-O H H H C1 5.5 ETHANOL There are 2 main ways to make ethanol • 1) FERMENTATION • Sugar from plants is broken down by enzymes in yeast • Sugar + Yeast  Ethanol + Carbon Dioxide • 80% of ethanol is made this way • + Uses renewable resources • Takes longer to produce • CO2 is given off • 2) ETHENE • Hydration reaction  water is added • Ethene + Steam  Ethanol • C2H4 + H2O  C2H5OH • + Continuous process – lots made! • + Produces no waste products • Requires lots of heat and energy • Relies on a non-renewable resource • USES FOR ETHANOL • Alcohol • Perfume • Rocket Fuel • Solvents • Antiseptic wipes A molecule of ethanol

C1 6.1 EXTRACTING VEGETABLE OIL There are 2 ways to extract vegetable oils from plants: • 1) PRESSING • 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 • 2) DISTILLATION • 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 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 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 Margarine • 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 bondsC=C  C-C • Now called a HYDROGENATED OIL • Reaction occurs at 60oC with a nickel catalyst Double bonds converted to single bonds 60oC + Nickel catalyst

Emulsifier molecule Oil droplet Water C1 6.3 EVERYDAY EMULSIONS Oils do not dissolve in water Emulsion  Where oil and water are dispersed (spread out) in each other  These often have special properties • EMULSION EXAMPLES • Mayonnaise • Milk • Ice cream • Cosmetics – face cream, lipstick etc • Paint • EMULSIFIERS • Stop water and oil separating out into layers • Emulsifiers have 2 parts that make them work: • Hydrophobic tail – is attracted to oil • Hydrophilic head – is attracted to water. It has a negative charge -

C1 6.4 FOOD ISSUES • FOOD ADDITIVES • Substance added to food to: • Preserve it • Improve its taste • Improve its texture • Improve its appearance • VEG OILS • Unsaturated Fats: • Source of nutrients like vitamin E • Keep arteries clear • Reduce heart disease • Lower cholesterol levels • ANIMAL FATS • Saturated Fats: • Are not good for us • Increase risk of heart disease • Increase cholesterol • E NUMBER • Additives approved for use in Europe • 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: Most lies within 10km of the surface Rest is within 100km but it’s hard to judge! Crust: Solid 6km beneath oceans 35km beneath land Core: Made of nickel and iron Outer core is liquid Inner core is solid Radius is 3500km Mantle Behaves like a solid Can flow very slowly 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 2:Green Plants, Bacteria & Algae = Oxygen PHASE 1:Volcanoes = Steam & CO2 PHASE 3:Ozone Layer = Animals & Us • Green plants, bacteria and algae ran riot in the oceans! • Green plants steadily converted CO2 into O2by the process of photosynthesis • Nitrogen released by denitrifying bacteria • Plants colonise the land. Oxygen levels steadily increase • Volcanoes kept erupting giving out Steam and CO2 • The early atmosphere was nearly all CO2 • The earth cooledand water vapour condensed to form the oceans • The build up of O2killed 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 CO2left Like this for a billion years!

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 • Molecules for life (amino acids) came on meteorites from out of space • Actual living organisms themselves arrived on meteorites • 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: • The main gases in the atmosphere today are: • Nitrogen  78% • Oxygen  21% • Argon  0.9% • Carbon Dioxide  0.04% • 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.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 LEVELSHave increased in the atmosphere recently largely due to the amount of fossil fuels we now burn

Understanding Atoms, Compounds & Elements: Essential Chemistry Concepts