Chemistry Revision Guide PDF

TABLE OF CONTENTS UNIT 1 MATTER 1 AND 2 UNIT 2 THE PERIODIC TABLE 3 AND 4 UNIT 3 STRUCTURE AND BONDING 5 AND 6 UNIT 4 ACIDS, BASES AND ALKILIES 7 AND 8 UNIT 5 ENERGETICS AND KINETICS 9 AND 10 UNIT 6 CHEMICAL CALCULATIONS...

TABLE OF CONTENTS UNIT 1 MATTER 1 AND 2 UNIT 2 THE PERIODIC TABLE 3 AND 4 UNIT 3 STRUCTURE AND BONDING 5 AND 6 UNIT 4 ACIDS, BASES AND ALKILIES 7 AND 8 UNIT 5 ENERGETICS AND KINETICS 9 AND 10 UNIT 6 CHEMICAL CALCULATIONS 11 UNIT 7 CHEMICAL REACTIONS 12 AND 13 UNIT 8 ORGANIC CHEMISTRY 14, 15 AND 16 0  MATTER SOLUBILITY CURVES DISSOLVING A solubility curve is a graph of solubility, measured Sand is insoluble in water – it does not dissolve in water, no matter in g/100 g water, against temperature in °C. how much you heat it or stir it. However, salt + sugar is soluble in Solubility curves for more than one substance are water - they dissolve in water to make solutions. During dissolving, often drawn on the same graph, allowing particles of solvent collide with particles of solute. comparisons between substances. MELTING POINT DETERMINATION Heating and cooling curves can be used to determine the melting and boiling point of a substance. Impurities lower the melting and boiling points of pure substances. Melting point determinations are often used a as test for purity CHANGING STATE HEATING AND COOLING CURVES Represent the effect of heating on particles SOLUTE AND SOLVENT A solute is the substance that dissolves to make a solution. In salt solution, salt is the solute A solvent is the substance that does the dissolving of the solute. It dissolves the solute. In salt solution, water is the solvent. Represent the effect of cooling a substance SUSPENSIONS A suspension is a heterogenous mixture, it separates over time COLLOIDS A colloid is one of the three primary types of mixtures, the other two are solutions and suspensions. In colloids, 1 substance is evenly dispersed in another. The substance being dispersed is referred to as being in the dispersed phase, while the substance in which it is dispersed is in the continuous phase. To be classified as a colloid, the substance in the dispersed phase must be larger than the size of a molecule but smaller than what humans can see with their bare eyes. 1 CLASSIFYING MATTER SEPARATION TECHNIQUES FILTRATION Separating an insoluble solid form, a liquid. For ex: chalk and water EVAPORATION Evaporating the solvent to only be left with the solute. For ex: with water + salt SIMPLE DISTILLATION Separates 2 miscible liquids with different melting points CHROMATOGRAPHY Process used for separating colours. For example: chlorophyll 2  THE PERIODIC TABLE CALCULATING NUMBERS OF SUBATOMIC PARTICLES ATOMIC STRUCTURE The symbol for an atom shows: mass number All atoms have a 23 central nucleus. It Na at the top, and its atomic number at the bottom. To calculate the numbers of is surrounded by 11 subatomic particles in an atom, use its atomic electrons which number and mass number: are all set in number of protons = atomic number shells. Protons + number of electrons = atomic number electrons have number of neutrons = mass number - atomic number electrical charges ELECTRON CONFIGURATION that are equal and Electrons in all atoms opposite. occupy energy levels, also called electron shells, Subatomic particle Relative mass Relative charge outside the nucleus. Different shells can hold Proton 1 +1 different numbers of electrons. The electrons in Neutron 1 0 an atom occupy the lowest available energy level first. This is the shell near the nucleus. Electron Very small -1 Shell Maximum ATOMIC AND MASS NUMBER First 2 ATOMIC NUMBER (Z) Second 8 The number of protons in an atom of an element is its Third 8 atomic number ISOTOPES MASS NUMBER (A) Isotopes are forms of an element that have the same number The sum of protons and neutrons in an element is (its of protons but different number of neutrons mass number Same atomic number and Different mass number RELATIVE ATOMIC MASS (RAM) The relative atomic mass of an element is the average mass of its atoms, compared to 1/12th the mass of a carbon-12 atom. The relative atomic mass, Ar, of an element is calculated from: The mass numbers of its isotopes The abundance of these isotopes 3  THE PERIODIC TABLE THE PERIODIC TABLE GROUPS METALS AND NON-METALS GROUP 1 – THE ALKALI METALS The elements can be placed in the periodic table. The Contains elements placed in a vertical column on the far position of an element provides information about its left of the periodic table. The elements in group 1 are properties. Most elements are metals, with different called the alkali metals. properties to those of non-metals. GROUP 7/17 – THE HALOGENS Contains non-metal elements placed in a vertical column on the right of the periodic table. The elements in group 7 are called the halogens. GROUP 0/8/18 – THE NOBLE GASES Contains non-metal elements placed in the vertical column on the far right of the periodic table. The elements in group 0 are called the noble gases. HORIZONTAL = PERIODS. There are 7 periods. Elements in the same period all have the same number of occupied electron shells (energy levels). TRANSITION METALS From left to right across a period, elements go from displaying metal characteristics to non-metallic properties. Most metals are transition metals. They include iron, copper and chromium. The transition elements are in the VERTICLE = GROUP. Elements belonging to one of the 18 groups will share similar central part of the periodic table. properties. Atoms of each element within a group have the same number of electrons in their outermost electron shell PERIODIC TABLE PATTERNS The periodic table arranges all chemical elements in special ways. Different types of chemical bonding, and patterns and trends can be observed in their arrangement. COMMON PATTERNS INCLUDE: - Physical state at room temperature - Atomic radius - Metallic nature PROPERTIES OF METALS AND NON-METALS - Chemical reactivity Metals Non-metals - Formation of ions - Acid-base character of oxides Appearances Shiny Dull State at room Half solid, half gases Solid temperature and 1 liquid Density High Low Strength Strong Weak Malleable or brittle Malleable Brittle Conduction of Poor Good electricity Type of oxide Basic or alkaline Acidic 4  STRUCTURE AND BONDING IONIC FORMULAE IONIC BONDING An ionic bond is the force of attraction that holds together + and – ions. It forms when atoms of a metallic element give up electrons to atoms of a non-metallic element. The figure below shows how this happens The formula for an ionic compound must contain the same number of positive and negative charges so that the charges are balanced and it is neutral overall. Write the formula: For ionic compound that will form between Ba2+ and Cl- 1. Balance charge with + and – ions 2. Write the + ion of metal first and the - ion Ba2+ Cl- Cl- 3. Write the number of ions needed as subscripts BaCl2 GIANT COVALENT MOLECULES COVALENT BONDING A covalent bond is formed when two atoms share a pair of electrons. Covalent bonding occurs in most non-metal elements, and in compounds formed between non- metals. These shared electrons are found in the Giant covalent structures contain very many atoms, each joined to outer shells of the atoms. Usually each atom contributes one electron to the shared pair of adjacent atoms by covalent bonds. electrons. The atoms are usually arranged into giant regular lattices - extremely strong structures because of the many bonds involved. METALLIC BONDING Electrical conductivity Thermal conductivity Malleability Ductility Shiny texture 5  STRUCTURE AND BONDING NAMING IONIC COMPOUNDS SIMPLE COVALENT MOLLECULES Simple molecules contain only a few atoms held together by covalent bonds. PROPERTIES OF SIMPLE MOLECULAR SUBSTANCES An example is carbon dioxide (CO2), the Low melting and boiling points - this is because little energy is needed molecules of which contain one atom of carbon to break the weak intermolecular forces. They typically exist as liquids bonded with two atoms of oxygen. or gases at room temperature. They have strong covalent bonds Low melting and boiling points - this is because within the molecules, and have weak intermolecular forces btw little energy is needed to break the weak molecules. Do not conduct electricity - this is because they do not intermolecular have any free electrons or an overall electric charge. forces. Do not conduct IONIC COMPOUNDS electricity - this is Ionic because they do compounds have not have any free electrons or regular structures, an overall electric called giant ionic charge. lattices. In a giant ionic lattice, there LEWIS DIAGRAMS are strong Steps for drawing a Lewis diagram: electrostatic forces of attraction acting 1. Count all the valence electrons in all directions between the oppositely charged ions. The structure 2. Determine the central atom (the element and bonding of ionic compounds explains their properties. there is only one of) 3. Draw single bonds to the central atom METALS ALLOYS 4. Put all remaining valence electrons on atoms In an alloy, there are atoms of different sizes. The smaller or bigger as lone pairs atoms distort the layers of atoms in the pure metal. This means that 5. Turn lone pairs into double or triple bonds to give every atom an octet (or duet) a greater force is required for the layers to slide over each other. The alloy is harder and stronger than the pure metal. 6  ACIDS, BASES AND ALKALIES ACIDS AND ALKALIES PH SCALE Acids form acidic solutions in water. Acids The pH scale measures the acidity or alkalinity of a solution. The pH produce hydrogen ions, H+ in aqueous of a solution can be measured using a pH probe, or estimated solution. using universal indicator and a color chart. For example: HCl(aq) → H+(aq) + Cl-(aq) Acidic solutions have pH values less than 7. Alkalis form alkaline solutions in water. Alkalis produce hydroxide ions, OH- in aqueous solution. For example: NaOH(aq) → Na+(aq) + OH- (aq) Alkaline solutions have pH values greater than 7. ACID RAIN A neutral solution is neither acidic, nor alkaline. Neutral solutions have a pH value of 7. REACTIONS OF ACIDS Acid + metal oxide -> Salt + Water Acid + metal hydroxide -> Salt + Water Acid + Alkali -> Salt + Water Acid + Metal Carbonate -> Salt + Water + Carbon Dioxide PRECIPITATION REACTIONS A precipitation reaction is one in which substances in solution are mixed and an insoluble product is Sulphur dioxide (SO2) is produced when fossil fuels containing made. The insoluble product is called sulphur impurities are burned a precipitate and can be seen as a solid forming in the reaction mixture. Nitrogen dioxide (NO2) is produced in cars with petrol engines. The spark plugs used to ignite the fuel provide enough energy to break the strong bonds between the nitrogen atoms allowing them to combine with oxygen. This also happens naturally during lighting storms 7  ACIDS, BASES AND ALKALIES SALT FORMATION ENERGY CHANGES A soluble salt can be prepared by reacting an acid with a Neutralisation is an exothermic reaction. When an suitable insoluble reactant including: acid is added to an alkali (or vice versa) the a metal temperature increases until all of the reactants have a metal oxide been used up. When further reactant is added the a carbonate temperature begins to decrease as the reaction The insoluble reactant chosen depends on the salt required mixture cools down Hydrochlori Sulfuric acid Nitric acid c acid Copper(ll) Copper(ll) Copper(ll) Copper(ll) oxide chloride sulphate nitrate Aluminium Aluminium Aluminium Aluminium hydroxide chloride sulphate nitrate Zinc Zinc Zinc sulphate Zinc nitrate carbonate chloride PH CHANGE Bases are substances that can react with acids and neutralize them. They are typically metal oxides or hydroxides CuO(s) + 2HCl(aq) -> CuCl2(aq) + H2O(l) NaOH(aq) + HNO3(aq) -> NaNO3(aq) + H2O(l) OCEAN ACIDIFICATION The acidification of seawater causes many Base + Acid -> Salt + Water environmental effects like acid reactions with calcium carbonate in shells of marine invertebrates, dramatically reduced growth of species and reduce biodiversity in the ocean. Acid rain is a pollution problem caused by the release of acidic gases into the atmosphere. It contributes to pollution in a variety of ways including: damage to plants and the wildlife erosion of limestone buildings/structures corrosion (rusting) of iron bridges/structures 8  ENERGETICS AND KINETICS FACTORS AFFECTING RATES OF REACTION RATE OF REACTION COLLISION THEORY The rate of a reaction is a measure of how quickly a reactant is used up, or a product is formed. Mean rate of reaction= Quantity of reactant used / of product formed Time taken CALORIMETRY CALCULATIONS The amount of heat released or absorbed (energy transfer) in a chemical reaction can be measured practically using calorimetry and calculated using the equation below. Q=MC∆T INCREASE SURFACE AREA OF REACTANTS Q= energy transferred (joules) M= mass of water (grams) C= specific heat capacity ∆T=temperature change (K or ºC) Example question: how many joules of heat are given off when 5.0f of water cool from 75ºC to 25ºC? Q=x M=5.0g ∆T=75–25=50ºC C=4.18J/gºC Q=mc∆T= (5.0) (4.18) (50) =1045J USE OF CATALYSTS IN THE REACTION INCREASE CONCENTRATION OF REACTANTS 9  ENERGETICS AND KINETICS FACTORS AFFECTING RATES OF REACTION CATALYSTS INCREASE CONCENTRATION OF REACTANTS CALORIMETRY A catalyst speeds up chemical reactions, but is not consumed by the reaction; catalyst can be recovered chemically Calorimetry is the unchanged at the end of the sped-up reaction A catalyst works process of measuring by providing different route, with lower Ea, for the reaction. the amount of heat released or absorbed Catalysts lower the energy barrier. during a chemical Heterogeneous catalysis: reaction. By knowing This involves the use of a catalyst in a different phase from the the change in heat, it reactants. Typical examples involve a solid catalyst with the can be determined whether or not a reactants as either liquids or gases. reaction is Homogeneous catalysis: exothermic (releases heat) or endothermic This has the catalyst in the same phase as the reactants. (absorbs heat). Typically, everything will be present as a gas or contained in a single liquid phase. RATE GRAPHS The rates of two or more reactions can be compared FUELS AND COMBUSTION using graph of mass or volume of product formed A fuel is any compound which has stored energy. Combustion against time. is burning a fuel in oxygen, which gives out heat energy and is called an exothermic reaction. Our main source of fuel is fossil fuels. 10  CHEMICAL CALCULATIONS MOLAR VOLUME CALCULATING PERCENTAGE CALCULATIONS 1 mole of any gas at room temperature and When using chemical formula, it is possible to calculate the pressure (20ºC and 1 atmosphere) occupies a percentage composition of the chemical. volume of 24dm3 % mass = (Total Ar of the element ÷ Mr of the compound) × 100 THE MOLE CONCEPT PERCENTAGE MASS CALCULATIONS Molar Or C= concentration= N Moles V Volume CONCENTRATION OF A SOLUTION EMPIRICAL FORMULAE c =concentration (mol/dm3) The empirical formula of a compound is the simplest whole number n = moles (mol) ratio of atoms of each element in the compound. It is determined V = volume of solution using data from experiments and empirical. For example, (dm3) the molecular formula of glucose is C6H12O6 but the empirical formula is CH2O. This is because we can divide each number in REACTING AMOUNTS C6H12O6 by 6 to make a simpler whole number ratio. To calculate the mass of a product given the mass of a reactant, use the following steps: 1. Calculate no. moles of reactant: No. moles = mass/ Mr 2. Determine mole ratio of reactant to product: Ensure the equation is balanced 3. Calculate no. moles of product: Use the mole ratio 4. Calculate mass of product: Mass=moles x Mr INDEPENDENT VARIABLE: what we change DEPENDENT VARIABLE: what we want to find CONTROLLED VARIABLE: what we keep the same 11  CHEMICAL REACTIVITY REACTIONS OF METALS WITH WATER REACTIONS OF METALS WITH DILUTE ACIDS When a metal reacts with water, a metal hydroxide and When a metal reacts with a dilute acid, a salt and hydrogen are formed. For example, sodium reacts rapidly with hydrogen are formed. For example, magnesium reacts cold water: rapidly with dilute hydrochloric acid: Sodium + water → sodium hydroxide + hydrogen Magnesium + hydrochloric acid → magnesium chloride + 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g) hydrogen In general, the more reactive the metal, the more rapid the Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g) reaction The more reactive the metal, the more rapid the reaction Potassium sodium: violent reaction with cold water is. A metal below hydrogen in the reactivity series will not Calcium: quick reaction with cold water react with dilute acids Magnesium: slow reaction in cold water and reacts moderately REACTIONS OF METALS WITH OXYGENS with steam Zinc: no reaction in cold water but does react with steam Metals react with oxygen to form basic metal Copper: no reaction with cold water or steam oxides (metal oxides that will neutralize acids) Potassium Potassium + Water à Hydroxide + Hydrogen Magnesium + Oxygen à Magnesium oxide 2K + 2H2O à 2KOH + H2 2Mg + O2 à 2MgO Lithium Copper + Oxygen à Copper oxide Lithium + Water à Hydroxide + Hydrogen 2Cu + O2 à 2CuO 2Li + 2H2O à 2LiOH + H2 Iron + Oxygen à Oxide Sodium 4Fe + O2 à 2Fe2O3 Sodium + Water à Hydroxide + Hydrogen 2Na + 2H2O à 2NaOH + H2 DISPLACEMENT REACTIONS A more reactive metal can displace a less reactive metal OXIDATION AND REDUCTION from its compounds. For example, magnesium is more Oxidation is the loss of electrons from a substance. It is also the gain of oxygen by a substance. reactive than copper. It displaces copper from copper Reduction is the gain of electrons by a substance. It is also the sulfate solution: loss of oxygen from a substance. Magnesium + copper sulfate → magnesium sulfate + THE REACTIVITY SERIES copper THERMITE REACTION aluminium + iron (III) oxide → iron + aluminium oxide 2Al + Fe2O3 → 2Fe + Al2O3 Aluminium has been oxidised. This means that the iron (III) oxide is the oxidising agent. We can also see that the iron (III) oxide has been reduced. This means that the aluminium is the reducing agent. 12  CHEMICAL REACTIVITY EXTRACTING METALS USING ELECTROLYSIS ELECTROLYSIS Metals are found in ores combined with other elements. During electrolysis, ionic substances are decomposed into Electrolysis can be used to extract a more reactive metal simpler substances when an electric current is passed through from the ore them. Electrolysis is used to extract and purify metals. Extracting aluminium Aluminium is a reactive metal that is extracted on a large- scale using electrolysis ELECTROCHEMICAL CELLS AND BATTERIES A simple electrochemical cell can be produced by dipping two different metals into an electrolyte and connecting them via wires and a voltmeter, bulb, motor, etc. The bigger the difference in reactivity between the two metals, the bigger the voltage produced. FUEL CELLS Fuels such as hydrogen can also be made to react with oxygen in a controlled manner to produce energy as electricity, not as heat. These fuel cells have the advantage of being more efficient than engines that burn fuels, they have fewer moving parts, and they are lighter and more sustainable. There are many different types of cell for different uses In non-rechargeable cells, e.g. alkaline cells, a voltage is produced until one of the reactants is used up. When this happens, we say the battery ‘goes flat’. In rechargeable cells and batteries, like the one used to power your mobile phone, the chemical reactions can be reversed when an external circuit is supplied. 13  ORGANIC CHEMISTRY ORGANIC CHEMISTRY IUPAC NAMING RULES Nº Prefix Suffix Structural formula Molecular Organic chemistry is the chemistry of carbon, an element that of C formula forms strong chemical bonds to other carbon atoms as well as many other elements like hydrogen, oxygen, nitrogen, and the 1 Meth CH4 halogens. Because of its versatility in forming covalent bonds, more than a million carbon compounds are known. 2 Eth C2H6 ane 3 Prop C3H8 Organic compounds typically contain a relatively unreactive 4 But C4H10 hydrocarbon part joined to another atom or atoms known as a functional group which is largely responsible for the reactions 5 Pent C5H12 of the compound. ALKANES 6 Hex C6H14 Alkanes are a homologous series of saturated hydrocarbons. 7 Hept C7H16 General formula: CnH2n+2 Homologous series: means that they have similar chemical 8 Oct C8H18 properties to each other and they have trends in physical properties. For example, as the chain length increases, FERMENTATION their boiling point increases. Saturated hydrocarbons: means that their carbon atoms During fermentation; sugar (glucose) form plant material is are joined to each other by single bonds. This makes them converted into ethanol and carbon dioxide. This typically takes relatively unreactive, apart from their reaction with oxygen place at temperatures of around 30ºC. The enzymes found in in the air – which we call burning or combustion. singles-celled fungi(yeast) are the natural catalysts that can make this process happen CRACKING ALKANES 1. 2. Cracking is a reaction in which larger saturated hydrocarbon molecules are broken down into smaller, more useful hydrocarbon molecules, some of which are unsaturated: ALCOHOLS 1. The original starting hydrocarbons are alkanes. 2. The products of cracking include alkanes and alkenes The alcohols are a homologous series of organic compounds. They all contain the functional group –OH, which is responsible for the properties of alcohols. The names of alcohols end with ‘ol’, eg ethanol. Methanol CH3OH Ethanol C2H5OH Propanol C3H7OH 14  ORGANIC CHEMISTRY ALKENES ADDITION POLYMERS Alkenes form a homologous series of unsaturated Polymers are long chain molecules hydrocarbons that occur naturally in living things Hydrocarbons, because they are compounds containing and can also be made by chemical hydrogen and carbon only processes in industry. Unsaturated, because they contain a C=C double bond, Different polymers have which means that they have two fewer hydrogen atoms than the corresponding alkane different properties. This means that The C=C bond is the functional group in the alkenes. It different polymers have different is responsible for the typical reactions of alkenes. uses. General Formula: CnH2nr Polymer Properties Uses n= number of carbon atoms in the molecule. Flexible, cheap, can Carrier bags, shampoo Alkene Structural formula Molecular Ball and stick Poly(ethene) be made into thin bottles, food wrap formula models films Ethene C2H4 Flexible, strong, Buckets, bowls, crates, Poly(propene) resist shattering ropes, carpets Tough, electrical Insolation for insulator, can be electrical wires, Propene C3H6 Poly(chloroethene) made hard or windows, gutters, flexible pipes Slippery, chemically Non-stick coatings for Butene C4H8 Poly unreactive pans, containers for (tetrafluoroethene) laboratory substances ACIDS AND ESTHERS CONDENSATION POLYMERS Carboxylic acids are a homologous series of organic acids. All-natural polymers are condensation polymers. The monomers Carboxylic acids are weak acids which react with alcohols to contain two functional groups. A water molecule is formed every form compounds called esters time a link is formed between the monomers. Sometimes known as A-B polymers 15  ORGANIC CHEMISTRY TYPES OF PLASTICS CARBON FOOTPRINT Low density plastics (e.g. LDPE, low density polythene) have What is a carbon footprint? a lot of branching The amount of carbon released into the atmosphere by a certain group, community, or individual when performing a certain activity. How can we reduce our carbon footprint? The use of renewable energy such as solar, nuclear, or hydro. Reduce the use of electricity. The use of efficient cars, the reduction of meat consumption and less travel. The use of a bike or walking rather than a car would be a large step in the right direction. Plane travel is also a very large pollutant and the use of trains (electric) or not travelling is preferred. Thermosetting plastics contain covalent cross links between the polymer chains giving extra strength and thermal properties CARBON CYCLE FRACTIONAL DISTILATION OF CRUDE OIL Crude oil is a mixture of hydrocarbons formed from the remains of simple marine organisms over millions of years. Fractional distillation separates a mixture into a number of different parts, called fractions. A fraction of crude oil is a mixture of chemicals in the crude oil that have similar boiling points. 16