CIE IGCSE Chemistry 0620 Past Paper PDF

 TABLE OF CONTENTS 3 CHAPTER 1 The Particulate Nature of Matter 4 CHAPTER 2 Experimental Techniques 5 CHAPTER 3 Atoms, Elements and Compounds 7 CHAPTER 4 Stoichiometry 8 Electricity and Chemistry CHAPTER 5 9...

 TABLE OF CONTENTS 3 CHAPTER 1 The Particulate Nature of Matter 4 CHAPTER 2 Experimental Techniques 5 CHAPTER 3 Atoms, Elements and Compounds 7 CHAPTER 4 Stoichiometry 8 Electricity and Chemistry CHAPTER 5 9 CHAPTER 6 Chemical Energetics 10 CHAPTER 7 Chemical Reactions 12 CHAPTER 8 Acids, Bases and Salts 14 CHAPTER 9 The Periodic Table 15 CHAPTER 10 Metals 16 CHAPTER 11 Air and Water 18 CHAPTER 12 Sulfur 18 CHAPTER 13 Carbonates 19 CHAPTER 14 Organic Chemistry  CIE IGCSE CHEMISTRY//9093 1. THE PARTICULATE NATURE OF MATTER 1.1 Kinetic Particle Theory PROCESS HEAT ENERGY EXO/ENDOTHERMIC Melting Gained Endothermic HeatINCREASES HEAT increases Boiling Gained Endothermic Condensing Lost Exothermic  When a solid is heated, particles vibrate faster about a fixed point causing particles to move further apart and Freezing Lost Exothermic so solid expands Sublimation Gained Endothermic  When particles gain sufficient energy to overcome Reverse Lost Exothermic strong forces of attraction, they move out of their fixed sublimation position and can slide over each other in a continuous random motion – solid has melted. 1.3 Heating Curve  Particles in liquid have energy to move around but are still close to each other and do not have enough energy to overcome the forces that hold them close to each other.  If more heat’s supplied, particles move faster until they have enough energy to overcome the forces of attraction. Particles escape the liquids surface and move around in continuous rapid motion – the liquid has boiled  In the vapor, the particles move in rapid random motion. 1.4 Diffusion This movement is due to collision of vapor particles with  Diffusion is the spreading of one substance through air particles. another from a region of high concentration to a region of low concentration due to the continuous random 1.2 States of Matter motion of particles. SOLID LIQUID GAS  Evidence for diffusion:  Strong forces  Weaker  Almost no  In liquids: potassium manganate of attraction attractive intermolecular (VII) in a beaker of water between forces than forces  In gases: a gas jar of air and a gas particles solids  Particles far jar of bromine connected  Fixed pattern  No fixed apart, and  Factors that affect the rate of diffusion: (lattice) pattern, liquids move quickly  Temperature increases → rate of diffusion increases  Atoms vibrate take up the  Collide with  Lower density gas → rate of diffusion is higher but can’t shape of their each other and change container bounce in all position ∴  Particles slide directions fixed volume past each and shape other. PAGE 3 OF 22  CIE IGCSE CHEMISTRY//9093 2. EXPERIMENTAL TECHNIQUES  Interpreting simple chromatograms: o Number of rings/dots = number of substances 2.1 Measurement o If two dots travel the same distance up the paper VARIABLE APPARATUS they are the same substance.  Time  Stopwatch or Clock o You can calculate the Rf value to identify a substance, given by the formula:  Thermomemeter (liquid in glass,  Temperature thermistor or thermocouple) 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑚𝑜𝑣𝑒𝑑 𝑏𝑦 𝑠𝑜𝑙𝑢𝑡𝑒  Mass  Balance 𝑅𝑓 𝑉𝑎𝑙𝑢𝑒 = 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑚𝑜𝑣𝑒𝑑 𝑏𝑦 𝑠𝑜𝑙𝑣𝑒𝑛𝑡  To make colourless substances visible, use a locating Measuring Volume: agent: o Dry paper in oven o Spray it with locating agent o Heat it for 10 minutes in oven  Assesing purity from m.p./b.p: o Pure substances have a definite, sharp m.p./b.p. o Substance+impurity has lower m.p. and higher b.p. o More impurity means bigger change 2.3 Filtration  Mixture goes in a funnel with filter paper, into a flask. Measuring Gas  Residue is insoluble and stays at top. Beaker Burette Pippette Cylinder Syringe  Filtrate goes through 2.2 Critertia of Purity  Paper chromatography: o Drop substance to center of filter paper and allow it to dry o Drop water on substance, one drop at a time o Paper + rings = chromatogram. o Principle: Difference in solubility separates different pigments o Substances travel across paper at different rates which is why they separate into rings o Method works because different substances travel at different levels of attraction to it 2.4 Crystallization  Some water in the solution is evaporated so solution becomes more concentrated.  A drop is placed on a slide to check if crystals are forming.  Solution is left to cool and crystallise.  Crystals are filtered to remove  Stationary phase is material on which separation takes solvent. place  Mobile phase consists of the mixture you want to separate, dissolved in a solvent. PAGE 4 OF 22  CIE IGCSE CHEMISTRY//9093 2.5 Simple Distillation If one solid is magnetic, can use a magnet e.g. sand and  Impure liquid is heated iron fillings  It boils, and steam rises into the condenser SOLVENT IT DISSOLVES…  Impurities are left behind Water Some salts, sugar White spirit Gloss paint Condenser is cold so steam condenses to the pure liquid Propanone Grease, nail polish and it drops into the beaker Ethanol Glues, printing inks, scented substances 2.8 Choosing a Suitable Method METHOD OF SEPARATION USED TO SEPARATE Filtration A solid from a liquid Evaporation A solid from a solution Crystallization A solid from a solution Simple Distillation A solvent from a solution Fractional Distillation Liquids from each other Chromatography Different substances from a 2.6 Fractional Distillation solution  Removes a liquid from a mixture of liquids, because liquids have different b.p.s 3. ATOMS, ELEMENTS AND COMPOUNDS  Mixture is heated to evaporate substance with lowest b.p. 3.1 Atomic Structure and the Periodic Table  some of the other liquid(s) will evaporate too. MASS PARTICLE RELATIVE CHARGE  A mixture of gases condense on the beads in the (ATOMIC MASS ) fractional column. Proton +1 1  So the beads are heated to the boiling point of the Neutron 0 1 lowest substance, so that substance being removed Electron -1 1⁄1837 cannot condense on the beads.  Proton number: number of protons in an atom (and  The other substances continue to condense and will drip number of electrons in an atom) back into the flask.  Nucleon number: number of protons + neutrons in an The beaker can be changed after every fraction atom.  In the periodic table o The proton number increases by 1 when you go to the right o When you go one element down, you increase proton number by 8 in the first 3 periods (transition elements not included)  Isotopes: atoms of same element with different no. of neutrons o E.g. Carbon 12 and Carbon 14. o Two types: non-radioactive isotopes and radioactive- isotopes which are unstable atoms that break down giving radiations o Medical use: cancer treatment (radiotherapy) – rays 2.7 Seperating Mixture of Two Solids kill cancer cells using cobalt-60  Can be done by dissolving one in an appropriate solvent o Industrial use: to check for leaks – radioisotopes (tracers) added to oil/gas. At leaks radiation is  Then filter one and extract other from solution by detected using a Geiger counter. evaporation PAGE 5 OF 22  CIE IGCSE CHEMISTRY//9093  Electrons are arranged in electron shells. PROPERTY REASON  Atoms want to have full outer shells (full set of valency Form giant lattice Cations and anions attract electrons), this is why they react. High m.p. and b.p. Strong bonds between ions  Noble gases have full outer shells so they have no need Don’t conduct electricity Ions can’t move to react. when solid  Electron shell structure: 2, 8, 8, 18. Conduct electricity when Ions can move  More reactive elements have a greater desire to have a molten/aqueous full outer shell, so also form more stable compounds. Usually soluble in water Not required 3.2 Bonding: the Structure of Matter 3.4 Molecules and Covalent Bonds  Element: substance that cannot be split into anything  When atoms share 𝑒̅s to obtain a noble gas electron simpler, in a chemical reaction. Each element has a structure unique proton number.  Covalent bonding takes place between non-metals only  Mixture: two or more elements mixed together but not chemically combined SINGLE BOND DOUBLE BOND TRIPLE BOND  Compound: substance in which two or more different elements are chemically combined METALS NON-METALS Strong Brittle 2𝑒̅s shared 4𝑒̅s shared 6𝑒̅s shared Poor conductors of heat & Good conductors of heat (1 from each (2 from each (3 from each electricity (except & electricity atom) atom) atom) graphite) PROPERTY REASON Lower m.p. and b.p. than High m.p. and b.p. Low m.p. and b.p. Weak intermolecular forces metals High density Low density Usually liquid, gas or low of attraction between Forms basic oxides Forms acidic oxides m.p solid molecules Forms cations in reactions Forms anions in reactions Don’t conduct electricity No mobile ions/electrons Malleable and ductile Usually insoluble in water Not required Sonorous  Example: Some are magnetic  Alloy: Mixture of two or more metals or mixture of one or more metal with a non-metal, to improve its properties 3.5 Macromolecules 3.3 Ions and Ionic Bonds DIAMOND GRAPHITE SILICON DIOXIDE  Chemical bond formed by transfer of 𝑒̅s from one atom to another  Metals lose 𝑒̅s to form cations, non-metals gain 𝑒̅s to form anions  Positive cations & negative anions attract to each other  Four bonds  Three bonds  Makes up sand  Strong electrostatic force of attraction between positive  High m.p.  Made of flat  Each Si is bonded cations and negative anions is called ionic bonding  Doesn’t conduct sheets to 4 oxygen atoms,  Used for cutting  Held together by and each oxygen is as is srongest weak forces so is bonded to 2 silicon known soft used as a atoms substance lubricant  it has a high m.p.  Conducts electricity and is hard, like as it has one free e- diamond PAGE 6 OF 22  CIE IGCSE CHEMISTRY//9093  Melting point: high - structure made up of strong 4.4 Masses covalent bonds  Relative atomic mass (Ar): mass of one atom of an  Electrical: don’t conduct electricity - have no mobile ions element relative to one twelfth of the mass of one atom or electrons, except for graphite of Carbon-12  Strength: hard - exists in tetrahedral structure but  Relative molecular mass (Mr): sum of relative atomic graphite is soft masses of all the atoms in one molecule of the compound 3.6 Metallic Bonding 4.5 The Mole Concept  A mole of a substance is the amount that contains the same number of units as the number of carbon atoms in 12 grams of carbon-12  A mole is the Ar or Mr expressed in grams e.g. 1 mole of Carbon-12 is equal to 12 grams.  It is equal to 6.02 × 1023 atoms, this number is called Avogadro’s constant. 4.6 Number of Moles 𝑚𝑎𝑠𝑠 Positive ions held together by electrons – acts like glue 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑀𝑜𝑙𝑒𝑠 = 𝑚𝑜𝑙𝑎𝑟 𝑚𝑎𝑠𝑠 4. STOICHIOMETRY 4.7 Moles in Gases  Balancing equations: a chemical equation is balanced 𝑉𝑜𝑙𝑢𝑚𝑒 = 𝑁𝑜. 𝑜𝑓 𝑀𝑜𝑙𝑒𝑠 × 24𝑑𝑚3 when there are equal number of atoms and charges on both sides of the equation 4.8 Concentration  State symbols: 𝑛𝑜. 𝑜𝑓 𝑚𝑜𝑙𝑒𝑠 𝐶𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 = o (s) = solid 𝑣𝑜𝑙𝑢𝑚𝑒 o (l) = liquid  Moles per dm3 o (g) = gas o 1mol/dm3 = 1M o (aq) = aqueous solution  Grams per dm3, g/dm3 4.1 Valency Table 4.9 Molecular Formulae NAME FORMULA VALENCY  The formula using the actual number of atoms in a Nitrate NO3- 1 molecule Hydroxide OH- 1 4.10 Empirical Formulae Acetate/ CH3COO- 1  This is the simplest ratio of the atoms in a compound ethanoate  For example: Carbonate CO32- 2 o Molecular formula of ethanol = C2H5OH Sulphate SO42- 2 o Empirical formula of ethanol = C2H6O Silicate SiO32- 2  To find out the empirical formula you: Phosphate PO43- 3 o Make the percent ratio into the simplest whole number ratio (NOTE: if given %s, use them as grams) 4.3 Ending of Names o Divide the coefficients of each element symbol by the  Compound ending with -ide only contain two different lowest coefficient elements  Compound ending with -ate contain oxygen 4.11 Percentages 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑝𝑟𝑜𝑑𝑢𝑐𝑡 (𝑝𝑢𝑟𝑒)  𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝑝𝑢𝑟𝑖𝑡𝑦 = 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑐𝑜𝑚𝑝𝑜𝑢𝑛𝑑 (𝑖𝑚𝑝𝑢𝑟𝑒) × 100 𝑎𝑐𝑡𝑢𝑎𝑙 𝑚𝑎𝑠𝑠 𝑜𝑏𝑡𝑎𝑖𝑛𝑒𝑑  𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝑦𝑖𝑒𝑙𝑑 = 𝑐𝑎𝑙𝑐𝑢𝑙𝑎𝑡𝑒𝑑 𝑚𝑎𝑠𝑠 × 100 PAGE 7 OF 22  CIE IGCSE CHEMISTRY//9093 5. ELECTRICITY AND CHEMISTRY 5.3 Electroplating  Decomposition of an electrolyte with the help of electric  Coating one metallic object with another metal using current electrolysis  Electrolyte:  For electroplating, you need: o Aq. solution of ionic substance or molten ionic salt o Anode made of metal you o Conducts electricity due to the presence of mobile want to electroplate object ions with  Electrodes: o Ions of same metal as anode o Rods which help current enter the electrolyte in solution o Inert electrodes: do not take part in the reaction o Object to be plated at o Reactive electrodes: take part in the reaction cathode  Used to: o Make things look better o Prevent corrosion 5.4 Uses PLASTIC & ALUMINUM COPPER CERAMICS  Used for  Used in  Used as electricity cables electrical wires insulators because: as it is: because they: o Light o A very good o Don’t conduct o Non- conductor electricity corrosive (not best) o Conduct heat o Good o Ductile poorly 5.1 Principle conductor  Plastic used for o Cheaper than casing in plugs At the Molten cathode Metal copper  Ceramics used to Electrolyte  Cables have support cables in At the anode Non-metal steel core, for electricity pylons strength Higher in reactivity then H+ H2 formed 5.6 Refining Metals At the cathode Lower in  This is purifying impure metals  Rules: Metal reactivity formed then H+ Aqueous o Cathode: thin strip of pure metal Electrolyte Halogen Halide Concentrated fomed o Anode: impure metal present Oxygen o Electrolyte: Aqueous Salt Solution of metal At the Dilute anode formed  Example: Halide not Oxygen present Formed 5.2 Examples ELECTROLYTE AT AT CATHODE ANODE Molten lead(II) bromide Lead Bromine Concentrated hydrochloric acid Hydrogen Chlorine Concentrated aqueous sodium Hydrogen Chlorine chloride PAGE 8 OF 22  CIE IGCSE CHEMISTRY//9093 AT THE ANODE AT THE CATHODE  Made of titanium  Made of steel  Chlorine gas evolved  Hydrogen cations  Unreacted ions (Na+, H+ reduced to H2 molecules and OH-) move through  Left Na+ and OH- which is porous membrane due aqueous sodium to difference in liquid hydroxide pressure  Net flow to the right  Reaction at Anode: Cu – 2e  Cu2+ (mass decreases) 6. CHEMICAL ENERGETICS  Reaction at Cathode: Cu2+ + 2e  Cu (mass increases) 6.1 Energetics of a Reaction 5.7 Basics  Exothermic reaction: one that releases heat energy into  Electrolysis is a way to decompose compounds, using the surrounding electricity.  Endothermic reaction: one which absorbs heat energy  Reduction of positive cations happens at the cathode from the surroundings  Oxidation of negative anions happens at the anode  Bond breaking is endothermic  For example:  Bond making is exothermic o At the anode: 2Cl- → Cl2 + 2e- o At the cathode: 2H+ + 2e- → H2 EXOTHERMIC REACTION ENDOTHERMIC REACTION  Energy given out to the  Energy is taken in from 5.8 Extraction of Aluminium surroundings the surroundings  The main ore of aluminium is bauxite – high m.p.  Surroundings become  Surroundings become  Aluminium (III) oxide (alumina) is dissolved in molten hot cold cryolite (Na3AlF6) – this mixture has a lower m.p.  Bond making –  Bond breaking – (industrially preferred) exothermic endothermic 6.2 Energy Level Diagrams  During electrolysis aluminium is produced at the carbon cathode and oxygen at the carbon anode.  Due to the high temp. the oxygen reacts with the graphite anode to form CO2 and so anode had to be 6.3 Bond Energy periodically replaced  This is the amount of energy consumed or liberated when a bond is broken or formed in kJ/mol 5.9 Electrolysis of Brine ∆𝐻 = 𝐵𝑜𝑛𝑑 𝐵𝑟𝑒𝑎𝑘𝑖𝑛𝑔 + 𝐵𝑜𝑛𝑑 𝐹𝑜𝑟𝑚𝑖𝑛𝑔  Brine is concentrated NaCl solution  If overall heat energy is negative, reaction is exothermic  Ions present: Na+, H+, Cl- and OH-  If overall heat energy is positive, reaction is endothermic 6.4 Production of Energy  A fuel is a substance which can be conveniently used as a source of energy.  Burning fuels (like oil) to form oxides is an exothermic reaction.  The heat from burning fuels is used in power plants to create steam from water and turn turbines. PAGE 9 OF 22  CIE IGCSE CHEMISTRY//9093  In order for any material to combust three things must 6.7 Radioactive Isotopes be present:  Uranium-235 can be used in nuclear power stations to o Fuel produce electricity o Heat  The radioactive isotope is bombarded by neutrons o Oxygen resulting in a lot of heat being produced  A good fuel would:  Small amount of radioactive fuel produces large amount o Be cheap of heat o Be available in large quantities  Advantages: lots of energy is from a small amount and o Ba a liquid at room temperature no CO2 o Produce a large amount of energy when combusted  Disadvantage: radioactive waste produced and non- o Not produce polluting gases renewable 6.5 Hydrogen 7. CHEMICAL REACTIONS  Burns explosively with oxygen, so it is used in rockets.  In a fuel cell, it combines with oxygen without burning. 7.1 Collision Theorey  Produced by reacting methane gas with steam  Collisions are needed for a chemical reaction to take ADVANTAGES DISADVANTAGES place  Produces a lot of energy  Difficult to transport as it  Successful collisions have enough activation energy at  Abundant on earth (sea) is a gas at room moment of impact to break preexisting bonds and form  Less pollutant temperature new bonds  Renewable fuel  Forms explosive mixture with air – very dangerous 7.2 Rates of Reaction  Rate of a chemical reaction is the concentration of 6.6 Simple Cells reactant used up or product made in a given time.  A cell is a device which converts chemical energy into  Unit = (mol/dm3)/s electrical energy and is composed of two metals of different reactivity connected by an external circuit and 7.3 Concentration an electrolyte  Increasing concentration of reactants increases rate of  The process works due to the different reactivity of reaction metals  This is because there are more particles per unit volume,  Consists of a negative pole (the more reactive metal) and so the collision rate between reacting particles increases, a positive pole (less reactive metal) and an electrolyte. therefore the successful collision rate increases, which  The greater the difference in reactivity of the two results in an increased rate of reaction. metals, the greater the voltage will be.  The electrons flow because one metal is more reactive, so it has a stronger drive to give up its electrons.  The atoms give up electrons and enter the solution as ions. 7.4 Temperature  Increasing temperature increases the rate of reaction  This is because average kinetic energy of particles increase which means they are moving faster & also more particles have an energy greater/equal to activation energy, therefore successful collision rate increases, resulting in increased rate of reaction PAGE 10 OF 22  CIE IGCSE CHEMISTRY//9093  For gaseous reactants, if catalyst is solid metal, the catalyst provides a surface for reaction to take place on  The larger the surface are of the metal catalyst, the larger the area for reaction to take place therefore higher rate of reaction 7.5 Particle Size  Decreasing the particle size (increasing surface area) increases the rate of reaction  This is because there are more reactant particles exposed to collide, so the collision rate increases, therefore the successful collision rate increases,  Enzymes are protein molecules. They are biological resulting in an increased rate of reaction catalysts which speed up reactions but remain chemically unchanged at the end  Enzymes function best at optimum temperature and pH level otherwise they may denature and completely stop functioning 7.8 Measuring Rates of Reaction Experimentally  Large surface area can mean danger. For example, flour GAS EVOLVED MASS LOSS COLOUR dust and wood dust have large surface areas, and are CHANGE combustible. A spark from a machine, or a lit match, can cause an explosion. This also applies to gases from mines. 7.6 Pressure in Gaseous System  Increasing the pressure in a gaseous system increases the If a gas evolves, If a gas evolves, If a color change rate of reaction measure measure loss in occurs we can  The distance between particles volume of gas mass per unit measure the time is reduced under pressure produced per time by placing taken to go  There are more particles per unit time using on a balance cloudy unit volume, so the collision a gas syringe then putting a rate increases, therefore the cotton wool on successful collision rate increases, resulting in an top to allow gas increased rate of reaction. to pass but not 7.7 Catalyst to enter  A catalyst is a substance (usually a transition metal) 7.9 Light Causing a Chemical Reaction which speeds up a chemical reaction, but remains unchanged at the end  A photochemical reaction is one where light causes a reaction to occur. The higher the light intensity the  Adding a catalyst increases the rate of reaction higher the rate of the reaction.  A catalyst allows the reaction to go by an alternative  Photosynthesis: light provides energy for the reaction pathway with lower activation energy and chlorophyll is a dye that absorbs light.  More particles will have an energy greater than or equal carbon dioxide + water → (light + chlorophyll) → glucose + to the activation energy, therefore successful collision rate increases resulting in increased rate of reaction oxygen 6CO2 + 6H2O → (light + chlorophyll) → C6H12O6 + 6O2 PAGE 11 OF 22  CIE IGCSE CHEMISTRY//9093  Silver salts in photographic film: Silver bromide breaks  Potassium manganate is an oxidising agent and will go down, where light strikes the film, so silver is reduced. from purple to colourless Silver ions are reduced to silver.  To test for an oxidising agent, add a reducing agent (KI) 2AgBr(s) →2Ag(s)+Br2(g) and to test for a reducing agent, add an oxidising agent (KMnO4) 7.10 Reversible Reactions  A reversible reaction is a reaction in which reactants 8. ACIDS, BASES AND SALTS form products and the product(s) can then react or decompose to form the reactants 8.1 Properties of Acids  Example: CuSO4.5H2O (blue) ⇌ CuSO4(white) + H2O  An acid is a compound which when dissolved in water  (to get anhydrous, heat it, & to get hydrated form, add produces hydrogen ions (H+) and are described as proton water) donors (H+)  There are two types of equilibrium: static and dynamic.  Acids turn blue litmus indicator paper (or solution) red.  At dynamic equilibrium:  Have pH 1 to 6 o Rate of forward reaction = rate of reverse reaction  Acid + metal → salt + hydrogen gas o Concentrations of all reactants and products remain  Acid + base → salt + water constant  Acid + metal carbonate → salt + carbon dioxide + water o System is closed, and on large scale everything is  Strong acids completely ionize in water producing lots of constant H+ ions  Weak acids partially ionize in water producing few H+ ions 7.11 Equilibrium  Le Châtelier’s Principle: if conditions of an equilibrium 8.2 Properties of Bases are changed, the position of equilibrium moves to  Bases are insoluble substances which neutralize acids to oppose change form a salt and water only and are proton acceptors  Temperature: Temperature lowered; equilibrium moves  Alkalis turn red litmus indicator paper (or solution) to in exothermic direction. Temperature raised; equilibrium blue. moves in endothermic direction.  Have pH 8 to 14.  Pressure: Pressure raised; equilibrium moves to side  Base + acid → salt + water (+ CO2 when base is a metal with fewest gas molecules. Pressure lowered; carbonate) equilibrium moves to side with most gas molecules.  Base + ammonium salt → salt + ammonia gas + water  Concentration: Decreasing reactant concentration or  Strong alkalis completely ionize in water producing lots of increasing product concentration; equilibrium moves to OH- ions reactant side. Increasing reactant concentration or  Weak alkalis partially ionize in water producing OH- ions decreasing product concentration; equilibrium moves to product side. 8.3 Neutral  Neutral substances are pH 7. 7.12 Redox  Acidity in soil:  A redox reaction is one in which one species has been o Plants grow at a pH near 7. oxidized and another species has been reduced o If it is too acidic or alkaline they will not grow. OXIDATION MEANS: REDUCTION MEANS: o Acidic soil is fixed by adding lime.  Loss of electrons  Gain of electrons  Gain of oxygen  Loss of oxygen  Loss of hydrogen  Gain of hydrogen OIL RIG  Reducing agents are oxidized and oxidizing agents are  pH is the concentration of H+ ions per dm3 of solution reduced  Potassium iodide is a reducing agent & will go from colorless to red-brown, so is oxidized to produce I2 H2O2 + 2KI + H2SO4→I2 + K2SO4 + 2H2O PAGE 12 OF 22  CIE IGCSE CHEMISTRY//9093 8.4 Indicators 8.9 Starting with an Insoluble Base COLOR IN  Add insoluble base to acid and heat gently, it will INDICATOR COLOR IN ACID ALKALINE dissolve Phenolphthalein Colorless Pink  Keep adding until no more dissolves (reaction is done) Methyl orange Pink Yellow  Filter out the insoluble (excess) base Methyl red Red Yellow Red litmus Red Blue 8.10 Starting with an Alkali (Titration): Blue litmus Red Blue  Put a certain amount alkali in a flask  Add phenolphthalein 8.5 Types of Oxides  Add acid from a burette, stirring, until it goes colorless  Metal oxides are basic e.g. iron oxide and magnesium  Find out how much acid you used oxide  Repeat, to be more accurate  Non-metal oxides are acidic e.g. sulphur oxide and  Evaporate water from neutral solution carbon dioxide  Aluminum, zinc and lead form amphoteric oxides e.g. 8.11 Precipitation zinc oxide  Mix the two soluble salts, so they react together  Oxides which are neither acidic or basic are neutral e.g.  Filter the mixture to separate the products produced water and carbon monoxide (soluble and insoluble salt produced)  Wash the insoluble salt on the filter paper 8.6 Preparation of Salts  Dry the insoluble salt in a warm oven  A salt is a substance formed when all the replaceable hydrogen ions of an acid are replaced by metal ions or 8.12 Test for Aqueous Cations the ammonium ion EFFECT OF AQ. EFFECT OF AQ. o Salts can either be soluble or insoluble CATION NAOH AMMONIA White soluble SOLUBLE SALTS INSOLUBLE SALTS ALUMINUM precipitate formed White precipitate All sodium, potassium and (AL3+) giving a colorless formed ammonium salts solution All nitrates Ammonium gas Chlorides Except silver and lead AMMONIUM produced turns Except barium, lead and (NH4+) Sulphates damp red litmus blue calcium CALCIUM White precipitate No precipitate/ slight Potassium, sodium and All other carbonates (CA2+) formed white precipitate ammonium carbonates Light blue soluble COPPER Light blue precipitate precipitate formed 8.7 Type of Salts (CU2+) formed giving dark blue TYPE OF SALT REQUIRED ACID USED solution Sulphate Sulphuric acid IRON(II) Green precipitate Green precipitate Nitrate Nitric acid (FE2+) formed formed Chloride Hydrochloric acid IRON(III) Red-brown Red-brown Ethanoate Ethanoic acid (FE3+) precipitate formed precipitate formed 8.8 Starting with a Metal White soluble White soluble  Add excess metal to an acid precipitate formed precipitate formed ZINC (ZN2+)  When bubbling (hydrogen) stops the reaction is done giving a colorless giving a colorless  Filter off excess metal solution solution PAGE 13 OF 22  CIE IGCSE CHEMISTRY//9093 8.13 Test for Anions 9.2 Alkali Metals ANION TEST TEST RESULT  Lithium, sodium and potassium CARBONATE Add dilute nitric acid Bubble gas through CHEMICAL PROPERTIES PHYSICAL PROPERTIES (CO32-) limewater–from  Form ionic compounds  Good conductors of colorless to cloudy  React violently with heat and electricity. CHLORIDE Add nitric acid, then White precipitated chlorine  Are soft, compared to (CL-) aqueous silver nitrate formed  Burst into flames when other metals. BROMIDE Add nitric acid, then Cream precipitate heated with oxygen:  They have low densities (BR-) aq. silver nitrate formed O A red flame for for metals. - IODIDE (I ) Add nitric acid, then Bright yellow lithium  They have low melting aqueous silver nitrate precipitate formed O A yellow flame for and boiling points NITRATE Add aqueous sodium Gas produced turns sodium compared to most (NO3 )- hydroxide then add damp red litmus O A lilac flame for metals. aluminum paper blue potassium SULPHATE Add dilute nitric acid, White precipitate  Produce soluble white (SO42-) then add aq. barium formed compounds. nitrate  React with cold water. 8.14 Test for Gases Patterns GAS TEST AND TEST RESULT  Reactivity, density & softness increases down the group Ammonia (NH3) Damp red litmus paper turns blue  Melting and boiling points decreases down the group. Carbon dioxide Bubble gas through–from colorless  Reactivity increases as more electron shells means there (CO2) to cloudy is weaker attraction between nucleus & valency electron Chlorine (Cl2) Bleaches red/blue litmus paper so is lost more easily. Hydrogen (H2) Place lighted splint, squeaky pop 9.3 Halogens Oxygen (O2) Place glowing splint, splint relights PROPERTIES PATTERNS  Form colored gases, at  Down the group; size, 9. THE PERIODIC TABLE RTP: mass and density  The Periodic table is a method of classifying elements. o Fluorine is a yellow gas increases  They are arranged in order of increasing atomic number. o Chlorine is a green gas  Down the group, color  Made up of rows called periods and columns called o Bromine is a red liquid darkens groups o Iodine is a black solid  Reactivity decreases down  Metals are to the left and non-metals are to the right.  Are poisonous the group, because it has  Elements in the same group have similar properties.  Brittle and crumbly when to gain an electron, so the  Group number tells us the number of valency electrons solid closer the electron is to and the period number tells us about the number of  Do not conduct electricity the positive nucleus the electron shells  Form diatomic molecules more easily it will be gained, so atoms with 9.1 Periodic Trends fewer shells  Non-metals are on the right side of the periodic table,  Will react more easily. and metals are on the left.  Down a period of metals they become more reactive 9.4 Transition Metals  With non-metals, going down a period, the non-metal  High melting points (except mercury) becomes less reactive  Malleable and ductile  Good conductors of heat & electricity (silver is the best)  High density  Have no trend in reactivity PAGE 14 OF 22  CIE IGCSE CHEMISTRY//9093  Can be used as catalysts  Metals are often used as alloys because they have an  Form colored compounds increased range of uses and mixture of atoms gives an  Can form complex ions as they have variable valences irregular structure which stops layers sliding over each other easily; they are stronger 9.5 Noble Gases  This is what the structure of an alloy (a) looks like, PROPERTIES USES compared to a pure metal (b).  Density increases down  Helium- filling balloons the group and aircrafts because it  M.p. and b.p. increases is lighter than air and down the group will not catch fire.  Don’t conduct  Argon – filling (tungsten) electricity light bulbs to stop the 10.3 Reactivity Series  Don’t take part in filament reacting with K - Potassium  This places metals in order of their chemical reactions oxygen. Na - Sodium readiness to take part in chemical  Neon – is used in reactions Ca – Calcium advertising signs Mg –  Everything above hydrogen can because it glows red. Magnesium displace hydrogen from its acid, and hydrogen cannot reduce their 10. METALS Al – Aluminum oxides. C – Carbon  Metals above carbon, their oxides 10.1 Properties of Metals Zn – Zinc cannot be reduced by carbon. PHYSICAL CHEMICAL Fe – Iron  More reactive metals will react  High density  Form basic oxides Pb – Lead with cold water, and less reactive  Shiny when polished  Form positive ions H – Hydrogen will react slowly or not react with  Malleable Cu – Copper steam.  Ductile Ag – Silver  Aluminum seems unreactive  High m.p. And b.p. Au – Gold because it forms an oxide layer  Conductor of heat & which protects it electricity 10.4 Displacement Reactions 10.2 Alloys  These are reactions in which metals compete for oxygen  An alloy is two or more metals, or a metal and non-metal or anions which have been made molten and then mixed together  The more reactive metal will displace the less reactive  Alloys are used because they have improved qualities for metal from oxygen or an anion. a particular job over the pure metals  If more reactive metal has oxygen or an anion, no reaction occurs ALLOY MADE FROM SPECIAL USES  The bigger the difference in reactivity between the two PROPERTIES metals, the faster the reaction Brass Copper and Stronger and Electrical zinc more fittings, car 10.5 Thermal Decomposition resistant to radiators METAL METAL METAL NITRATE corrosion GROUP CARBONATE HYDROXIDE Bronze Copper and Harder, Statues, Group I tin stronger and springs, coins Do not Do not Metal nitrite and (except sonorous decompose decompose oxygen lithium) Stainless Iron, Does not rust Kitchen sinks, Group II, steel chromium cutlery, Metal oxide Metal oxide, lithium & Metal oxide and nickel chemical and carbon nitrogen dioxide transition and water plant dioxide and oxygen metals PAGE 15 OF 22  CIE IGCSE CHEMISTRY//9093 10.6 Extraction of Metals 10.9 Extracting Zinc METAL EXTRACTION METHOD  Ore = Zinc Blende = Zinc Sulphide (ZnS) K - Potassium  Zinc blende is roasted in air to convert it to zinc oxide Na - Sodium  Zinc oxide is reduced using coke to zinc and carbon More powerful/expensive method of extraction Ca – Calcium Reduction via monoxide in the furnace  As zinc is volatile, the gaseous metal is distilled leaving Ores more difficult to decompose Mg – electrolysis Magnesium less-volatile impurities behind. Al – Aluminum Zinc is condensed and liquid is run into mould. CARBON 10.10 Uses of Metal Zn – Zinc Reducing via heating  Aluminum Fe – Iron with Carbon or Carbon o Airplane/Cars (Strong/Low density/resistant to Pb – Lead Monoxide corrosion) HYDROGEN o Cans/Foil (Resistant to corrosion/malleable) Cu – Copper o Overhead cable (Good conductor of Ag – Silver Occur naturally electricity/ductile) Au – Gold  Zinc o Galvanizes Iron = coats it to stop it rusting 10.7 Extracting Iron o Alloys – brass/bronze  Ore = hematite (Fe2O3) o Batteries  Uses of slag o Sacrificial Protection o To make roads  Copper o To make cement o Electrical Wiring (Good conductor of  Coke burns with air electricity/Ductile) carbon + oxygen carbon dioxide o Cooking utensils (Malleable/good conductor of heat)  Carbon dioxide reacts with o Roofs (hard wearing against weather coke carbon dioxide + carbon carbon monoxide 11. AIR AND WATER  Carbon monoxide reduces Iron(III) oxide to iron iron(III) oxide + carbon monoxide iron + carbon dioxide 11.1 Tests for Water  The limestone reacts with impurities to form slag TEST TYPE OF TEST POSITIVE RESULT calcium carbonate + silicon dioxide calcium silicate + carbon dioxide Blue Cobalt(II) Chemical Paper turns from 10.8 Iron to Steel Chloride Paper blue to pink  Molten iron from blast furnace is poured into an oxygen Anhydrous Chemical From white furnace. Copper(II) powder to blue  Calcium oxide is added, and a jet of oxygen is turned on. Sulphate powder crystals  The calcium oxide neutralizes acidic impurities, forming Test m.p. and b.p. Physical m.p. at 0°C and slag that is skimmed off and oxygen burns the other b.p. at 100°C impurities away.  The carbon content is checked continually until it is just 11.2 Purification of Water right then the oxygen is turned off.  Water is pumped into screens, which remove solid o Mild Steel (0.25% carbon) – Used in machinery and floating debris. car bodies  Aluminum sulfate is added to coagulate (stick together) o Medium carbon steel (0.5%) – Used in railway lines small pieces of clay so that they are easily removed. o High carbon steel (1.5% carbon) – Used in knives and  The water is then filtered through coarse sand to remove blades larger, insoluble debris.  The water encounters more flocculants (chemicals that make particles move down to bottom of tank) and is filtered again through fine sand. PAGE 16 OF 22  CIE IGCSE CHEMISTRY//9093  Chlorine gas is bubbled through the water to kill  It is compressed, causing it to heat up. Cooled by bacteria. This makes the water slightly acidic, so to recycling cold air reverse this appropriate amounts of sodium hydroxide  The cold compressed air is passed through a jet, into a (an alkali) is added. larger space. It expands rapidly, making it very cold.  Some countries also add fluorine  This is repeated, cooling the air more. By -200°C it is liquid except for neon and helium. These gases are 11. 3 Use of Water removed. They can be separated from each other by AT HOME IN INDUSTRY absorption on charcoal.  Drinking  Dissolve  The liquid air is pumped into the fractioning column.  Cooking  wash and cool things There it is slowly warmed up. The gases boil off one by  Washing  In power stations where one, and are collected in tanks or cylinders.  On farms for animals & steam is used to turn  Sources of methane: oil and natural gas, decomposition crops turbines of vegetation, and waste gases from digestion in animals 11.4 Air 11.7 Catalytic Convertor  Clean air is composed of approximately  In the combustion engine, insufficient amounts of o 79% nitrogen oxygen lead to incomplete combustion of the carbon o 20% oxygen containing fuel o Remainder: noble gases, water vapor & carbon  Gases produced: (a) carbon monoxide (b) oxides of dioxide nitrogen  A catalytic convertor catalyzes the reduction of NO2 to 11.5 Pollutants in Air nitrogen gas N2 and catalyzes the oxidation of CO to CO2 POLLUTANT SOURCE PROBLEMS CAUSED Reacts with 11.8 Rust Preventition Incomplete haemoglobin,  Coating with something to prevent contact with air and Carbon moisture combustion of preventing it from Monoxide o Plastic, paint and grease carbon-containing carrying oxygen; CO o Electroplating with tin or chromium substances death due to oxygen o Galvanising: dipping in molten zinc starvation  Sacrificial protection: attaching a piece of metal that is Irritates eyes and Sulphur From combustion of more reactive that iron to object, commonly magnesium throat, causes or zinc. This will corrode in the place of iron. Dioxide fossil fuels which respiratory problems SO2 contain sulfur and causes acid rain 11.9 Fertilizer Oxides of Causes respiratory  NPK used in fertilizers because: Nitrogen From car exhausts problems and forms o Nitrogen is needed for chlorophyll and other proteins. NOx acid rain o Phosphorus helps roots grow and crops ripen. From burning of o Potassium helps make proteins and resist diseases. Causes damage to Lead petrol as lead is  All alkalis (except ammonia) will react with ammonium brain and nerve cells compounds, removing ammonia, for example: compounds added to it for better in young children performance 𝐶𝑎𝑙𝑐𝑖𝑢𝑚 ℎ𝑦𝑑𝑟𝑜𝑥𝑖𝑑𝑒 + 𝐴𝑚𝑚𝑜𝑛𝑖𝑢𝑚 𝑐ℎ𝑙𝑜𝑟𝑖𝑑𝑒 → 𝐶𝑎𝑙𝑐𝑖𝑢𝑚 𝐶ℎ𝑙𝑜𝑟𝑖𝑑𝑒 + 𝑊𝑎𝑡𝑒𝑟 + 𝐴𝑚𝑚𝑜𝑛𝑖𝑎 11,6 Fractional Distillation of Air 11.10 Greenhouse Gases  Air is filtered to remove dust  The greenhouse gases are: carbon dioxide and methane.  Water vapor and carbon dioxide removed, (because they  They stop heat escaping in to space. would freeze and block the pipes):  Too much greenhouse gases leads to climate change. o air is cooled until water vapor condenses  This will cause the ice poles to melt, rising sea levels, o then passes over absorbent beads to trap carbon more droughts, storms, floods and famine; global dioxide warming PAGE 17 OF 22  CIE IGCSE CHEMISTRY//9093 11.11 Formation of Carbon Dioxide 12.2 Uses  Carbon dioxide is produced whenever carbon or any of SULFUR SULFUR DIOXIDE its compound are completely burned in excess oxygen  As a food preserver; kills  Manufacture of  It is also formed as a product of respiration bacteria sulphuric acid  It is produced as product of reaction between an acid  As a bleach in the  To bleach wool, silk and and carbon manufacture of wood wood pulp for making  From the thermal decomposition of a carbonate pulp for paper paper  In car batteries as  As a sterilising agent in 11.12 Haber Process electrolyte making soft drinks and  Industrial manufacture of ammonia NH3  In manufacture of jam, and in drying fruit; sulphuric acid (through stops growth of bacteria N2 (g) + 3H2 (g) ⇌ 2NH3 (g) Contact process) and moulds.  Raw materials: o Nitrogen: from the air 12.3 Contact Process o Hydrogen: methane + steam → carbon dioxide +  Sulphur is first burned in air producing sulphur dioxide hydrogen  It is then mixed with more air and passed over four  Essential conditions: separate beds of catalyst, Vanadium (V) oxide, at 450°C o Temperature: 450°C to form sulphur trioxide o Pressure: 200atm  It is then dissolved in concentrated sulphuric acid o Catalyst: Iron forming a thick fuming liquid called oleum 11.13 Carbon Cycle  It is then mixed carefully with water to form concentrated sulphuric acid.  Essential conditions: o Catalyst: Vanadium (V) oxide o Temperature: 450°C o Pressure: 2atm 12.4 Properties of Sulfuric Acid  Forms salts called sulphates  When concentrated, it’s a dehydrating agent, and a thick oily liquid  It turns blue litmus red  It is a strong acid and has the properties of a typical strong acid: reacts with bases, low pH, high conductivity 13. CARBONATES 12. SULFUR 12.1 Sources  Found as an element, in large underground beds  Found around the rims of volcanoes.  It occurs in metal ores e.g. lead sulphide  Sulphur compounds also occur naturally in the fossil fuels e.g. coal  Lime is manufactured by limestone by heating  CaC03 + heat → CaO + CO2 PAGE 18 OF 22  CIE IGCSE CHEMISTRY//9093  Uses of quick lime: 14.4 Name of Compounds o Making steel from iron Name ending → compound-type name o To neutralise acidity in soil  “ane” → alkane o Drying agent in industry  “ene” → alkene  Uses of slaked lime and lime:  “ol” → alcohol o Neutralise acidity in soil, and in lakes affected by acid  “oic acid” → carboxylic acid rain,  “yl”, “oate” → ester o Neutralising acidic industrial waste products, e.g. flue gas desulphurisation 14.5 Alkanes  Uses of limestone: General formula = CnH2n+2 o Making cement: made by mixing limestone with clay, heating mixture strongly in a kiln, adding gypsum METHANE (N=1) ETHANE (N=2) (calcium sulphate), and grinding up the final solid to give a powder o Making iron from iron ore: limestone reacts with sand) forming slag (calcium silicate), which is then used for road building. PROPANE (N=3) BUTANE (N=4) 14. ORGANIC CHEMISTRY 14.1 Homologous Series  Each carbon atoms in an alkene has four covalent single  Homologous series: ‘family’ of similar compounds with bonds – this makes them quite unreactive. similar properties due to the presence of the same functional group. Combustion:  Characteristics of a homologous series:  Complete combustion: enough oxygen supply so water o all the compounds fit the same general formula and carbon dioxide form. o the chain length increases by 1 each time  e.g. CH4 + 2O2 → CO2 + 2H2O o as the chain gets longer, the compounds show a  Incomplete: is not enough oxygen to burn them cleanly gradual change in properties so either carbon monoxide and water or carbon and  Structural isomers: have the same chemical formula, but water form. different structures, they can be straight or branched e.g. 2CH4 + 3O2 → 2CO + 4H2O or e.g. CH4 + O2 → C + 2H2O 14.2 Fuels Chlorine substitution:  Fuels to know: o Coal  Sunlight or light is necessary o Natural gas: main constituent is methane  A chlorine atom replaces a hydrogen atom o Petroleum: a mixture of hydrocarbons which can be  This can happen to all hydrogen atoms if there is enough separated into fractions chlorine. e.g. CH4 + Cl2 → (light) → HCl + CH3Cl / CH2Cl2 / CHCl3 / 14.3 Uses of Petroleum Fractions CCl4  Refinery gas: bottled gas for heating and cooking Compounds = chloromethane / di/tri/tetrachloromethane  Gasoline fraction: fuel (petrol) in cars  Naphtha fraction: making chemicals  Kerosene/paraffin fraction: jet fuel, lamps  Diesel oil/gas oil fraction: fuel in diesel engines  Fuel oil fraction: fuel in ships and home heating systems  Lubricating fraction: lubricants, waxes and polishes  Bitumen: making roads PAGE 19 OF 22  CIE IGCSE CHEMISTRY//9093 14.6 Alkenes 14.8 Alkenes’ Addition Reactions General formula = CnH2n  With bromine: (the test for saturation) Functional group: C=C bond e.g. ethene (g) + bromine (aq) → 1,2-dibromomethane (l) (N=1) ETHENE (N=2)  With steam: forms alcohols with heat, pressure and a N/A catalyst e.g. ethene (g) + steam (g) ⇌ ethanol (l)  With hydrogen: double bond breaks down to for an PROPENE (N=3) BUT-1-ENE (N=4) alkane with heat, pressure and a catalyst e.g. ethene (g) + hydrogen (g) → ethane (g) 14.9 Alcohols General formula = CnH2n+1OH Cracking: Functional group: OH  Thermal decomposition reaction, in which an alkene METHANOL (N=1) ETHANOL (N=2) (and sometimes hydrogen) are produced from an alkane.  Cracking always produces short chain compound with a C=C bond e.g. Cracking of ethane will give ethene and hydrogen PROPANOL (N=3) BUTANOL (N=4) Formed by: FERMENTATION CATALYTIC ADDITION OF  Butane → Ethane + Ethene ; C4H10 → C2H6 + C2H4 STEAM TO ETHENE  Enzymes in yeast break  Ethene is obtained by SATURATED UNSATURATED down glucose to ethanol cracking long-chain HYDROCARBONS HYDROCARBONS and carbon dioxide, alkenes from oil.  Have NO double bonds  Have double bonds giving out heat  The ethene reacts with  Do not react with  React with aqueous  Can be done with steam (reversibly) in the aqueous bromine, so bromine, turning the substances that contain following conditions: the mixture stays mixture from orange to cellulose, starch or o 570°C orange. colourless. glucose o 60-70atm  Done by grinding source o Catalyst = phosphoric 14.7 Addition Polymerisation (e.g. grapes) and adding acid  A polymer is a compound with very long carbon chains enzymes to break down  Low temperature gives a made up of monomer units. cellulose and starch into better yield, but high  Poly(ethene) / Polythene: is a polymer produced from glucose. temperature is used to ethene by addition polymerization  Leave it to ferment. give a better rate of  Fractional distillation is reaction. used to get ethanol from the mixture Double bond splits and polymer is formed PAGE 20 OF 22  CIE IGCSE CHEMISTRY//9093 ADVANTAGES DISADVANATGES 14.11 Macromolecules  Renewable source  Lots of material needed  Large molecules built up from small units (monomers). FERMENTATION  Good use of waste so big tanks needed organic material  Fractional distillation is expensive  Slow process  Batch process  Different macromolecules have different units and/or  Fast  Oil is a non-renewable different linkages  Continuous processresource Example of: FROM ETHENE  Pure ethanol  Lot of energy to make  Smaller containerssteam and get right SMALL UNITS LINKAGES MACROMOLECULES conditions (MONOMERS)  Lot of ethene is un-  glucose  amide  protein reacted, (and then  amino acids  ester  starch recycled)  fatty acids  lipids  Ethanol burns well in oxygen, giving out plenty of heat, and glycerol as well as carbon dioxide and water.  Ethanol is used as a: USE STRUCTURE o Solvent: to dissolve things than water cannot. POLYTHENE  Plastic bags and Evaporates easily, so used as solvent in glues, printing gloves, clingfilm (low inks & perfumes density), mugs, bowls, o Fuel: added to or instead of petrol, because it burns chairs, dustbins (high cleanly density) POLYCHLOROE 14.10 Carboxylic Acids THANE (PVC)  Water pipes, General formula = CnH2n+1COOH wellingtons, hoses, Functional group: COOH covering for electricity METHANOIC ACID (N=1) ETHANOIC ACID (N=2) cables POLYPROPENE  Crates, ropes PROPANOIC ACID (N=3) BUTANOIC ACID (N=4)  Used as expanded POLYSTYRENE polystyrene in fast- Properties of Ethanoic Acid: food cartons,  Weak acid with high pH and low dissociation packaging, and  Formed by: insulation for roofs o Oxidation of ethanol and walls o With acidified potassium mangenate (VII)  Coated on frying pans  Carboxylic acids react with alcohols to give esters, in a to make them non- TEFLON condensation reaction, for example: stick, fabric protector,  Ethanoic acid + ethanol ⇌ ethyl ethanoate + water windscreen wipers, (alcohol = -yl & carboxylic acid = -oate) flooring PAGE 21 OF 22  CIE IGCSE CHEMISTRY//9093 Making nylon:  They collect in rivers, and get in the way of fish. Some  Uses: ropes, fishing nets and lines, tents, curtains river beds now contain a thick layer of plastic  Monomers are:  They blow into trees and onto beaches. So the place looks a mess. Tourists become put off. 14.13 Natural Macromolecules  Food’s main constituents are proteins, fats and carbohydrates. Proteins:  Proteins contain the same linkages (amide links) as nylon, but with different units. Their structure is:  No double bonds break, instead single bonds break, and new single bonds form.  The monomers are able to join to each other by  In digestion proteins are broken down into amino acids eliminating a small molecule: hydrogen chloride. (hydrolysis).  This reaction continues at each the two monomers. Fats:  Thousands of molecules join together, giving a  Fats are esters possessing the same linkage as Terylene macromolecule: (ester links) but with different units.  Soap is a product of the hydrolysis of fat. It is done using sodium hydroxide (as opposed to acid, in digestion). The