Topic 1 Matter and Substance Anion: A negatively charged ion. Formed when an atom gains at least one electron. Atom: The smallest part of an element that can exist. All substances are made up of atoms. Atomic nucleus: Positively charged object composed of protons and neutrons at the centre of every atom with one or more electrons orbiting it. Atomic number: The number of protons in the nucleus. Avogadro’s constant: The number of atoms, molecules or ions in a mole of a given substance. Cation: A positively charged ion. Formed when an atom loses at least one electron. Compound: A substance made up of two or more types of atoms chemically combined together. Concentration: The amount of substance (e.g. the mass) in a certain volume of a solution. Conductor: A material that contains charged particles which are free to move to carry electrical or thermal energy. Conservation of mass: A law which states that no atoms are lost or made during a chemical reaction so the mass of the products equals the mass of the reactants. Covalent bond: A shared pair of electrons between two non-metals. Dalton model: Dalton described atoms as solid spheres, stating that different spheres made up the different elements. Diamond: A giant covalent structure which is made up of carbon atoms each of which form four covalent bonds with four other carbon atoms. pmt-cc - - https://bit.ly/pmt-cc https://bit.ly/pmt-cc Electron: Negatively charged subatomic particle which orbit the nucleus at various energy levels. Very small relative mass (negligible). Electron shell: Different energy levels in atoms occupied by electrons. Electrostatic forces: The strong forces of attraction between oppositely charged ions. Element: A substance made up of only one type of atom. Empirical formula: The simplest whole number ratio of atoms of each element in a compound. Fullerenes: Molecules of carbon atoms with hollow shapes. The structures are based on hexagonal rings of carbon atoms but they may also contain rings with five or seven carbon atoms. Examples include graphene and C60. Giant covalent molecule: Molecules containing many atoms covalently bonded together. Graphene: A single layer of graphite with properties that make it useful in electronics and composites. Graphite: A giant covalent structure which is made up of carbon atoms each of which form three covalent bonds with three other carbon atoms. The atoms form layers of hexagonal rings which have no covalent bonds between them. There is one delocalised electron per carbon atom which is free to move to carry charge. Group (periodic table): A column of the periodic table. Elements in the same group have similar chemical properties. Intermolecular forces: The forces which exist between molecules. The strength of the intermolecular forces impact physical properties like boiling/melting point. Ion: An atom or molecule with an electric charge due to the loss or gain of electrons. Ionic bond: The bond formed between the oppositely charged ions when a metal atom loses electron(s) to form a positively charged ion and a non-metal gains these electron(s) to form a negatively charged ion. Ionic compound: Chemical compound formed of oppositely charged ions, held together by strong electrostatic forces. Isotope: Atoms of the same element with the same number of protons but a different number of neutrons. Lattice: A repeating regular arrangement of atoms/ions/molecules. This arrangement occurs in crystal structures. https://bit.ly/pmt-cc https://bit.ly/pmt-cc Limiting reactant: The reactant that is completely used up since it limits the amount of products formed. Mass number: The total number of protons and neutrons in the nucleus. Metallic bond: The bonds present in metals between the positive metal ions and negatively charged electrons. Metals: Elements that react to form positive ions. Found to the left and towards the bottom of the periodic table. Mole: The unit for amount of substance. The symbol for the unit mole is mol. Molecular formula: The actual ratio of atoms of each element present in a compound. Molecule: A group of at least two atoms held together by covalent bonds. Neutron: Neutral subatomic particle present in the nucleus of the atom. Relative mass of 1. Non-metals: Elements that react to form negative ions. Found towards the right and top of the periodic table. Period (periodic table): A row of the periodic table. Elements in the same period have the same number of electron shells. Periodic table: Table of elements arranged in order of increasing atomic number and such that elements with similar properties are in the same column (group). Polymers: Large long-chain molecules made up of lots of small monomers joined together by covalent bonds. Proton: Positively charged subatomic particle present in the nucleus of the atom. Relative mass of 1. Relative atomic mass: An average value that takes into account the abundances of the isotopes of the element. Relative formula mass: The sum of the relative atomic masses of the atoms in the numbers shown in the formula. It is numerically equal to the mass of one mole of a substance in grams. Simple molecules: Molecules containing a fixed number of atoms covalently bonded together. Subatomic particles: Particles smaller than an atom. Protons, neutrons and electrons are the three most common subatomic particles. https://bit.ly/pmt-cc https://bit.ly/pmt-cc Topic 2 - States of Matter and Mixtures Chlorination: A process used in water treatment where chlorine gas is injected into the water to kill any microbes. Chromatography: A process used to separate substances in a mixture. Separation of the substance depends on distribution between a mobile phase and a stationary phase. Crystallisation: A separation technique to obtain soluble solids from solutions. The process involves heating the solution until crystals start to form, leaving the solution to cool and then filtering the formed crystals from the solution. Filtration: A separation technique used to separate an insoluble solid from a solution. Fractional distillation: A process used to separate a mixture of liquids. The liquids have different boiling points so can be separated into different fractions within a fractionating column. Gas: The state of matter where the particles have the most energy. The particles in a gas are relatively spread out and move randomly in all directions. Ground water: Water which collects in rocks that then trap the water underground. Liquid: The state of matter where the particles are arranged randomly and close together. The particles are able to move past each other. Melting point data: Data which can be used to evaluate the purity of a substance. A pure substance should have a sharp melting point. Mixture: Contains at least two different elements or compounds which are not chemically bonded together. https://bit.ly/pmt-cc https://bit.ly/pmt-cc Mobile phase: The fluid (gas or liquid) which moves through the chromatography system, carrying the mixture which is to be separated. Paper chromatography: A type of chromatography which uses paper as the stationary phase and a solvent as the mobile phase. The solvent carries the mixture up the paper where the substances in the mixture then separate, depending on how soluble they are in the mobile phase. Particle theory: The theory which models the three states of matter by representing the particles as small solid spheres. Particle theory can help to explain melting, boiling, freezing and condensing. Potable water: Water that is safe for humans to drink. Pure substance: The chemistry definition of a pure substance is a substance which contains only one compound or element. The everyday definition of a pure substance is a substance which has nothing added to it, e.g. pure milk. Rf value: A value used in chromatography which is calculated as the distance travelled by the dissolved substance divided by the distance travelled by the solvent. It can be used to identify substances within a mixture. Sedimentation: A process used in water treatment to remove solids from the water. Suspended solids will fall to the bottom of the container and form a sediment, allowing them to be easily removed. Simple distillation: A separation technique used to separate a liquid from a solution. The solution is heated so that only the liquid with the lowest boiling point evaporates. This gas is then condensed in a condenser before being collected as a liquid. Solid: The state of matter where the particles hold a regular arrangement and have the least amount of energy. State symbols: The symbols used in chemical equations to denote the states of the chemicals reacting: (s) - solid, (l) - liquid, (g) - gas, (aq) - aqueous solution. Stationary phase: The nonmoving phase which the mobile phase passes over during chromatography. Waste water: Water from industrial, domestic, agricultural and commercial activity. It requires treatment before it is potable. https://bit.ly/pmt-cc https://bit.ly/pmt-cc Topic 3 - Chemical Changes Acid: Produces hydrogen ions (H+) in aqueous solutions with a pH range between 0 and 7. Alkali: Produces hydroxide ions (OH-) in aqueous solutions with a pH range between 7 and 14. Anode: The positive electrode. It is where negatively charged ions lose electrons in oxidation reactions. It is the electrode where oxygen is produced unless the solution contains halide ions - then the halogen is produced. Base: A substance which reacts with an acid in a neutralisation reaction to form a salt and water only. Cathode: The negative electrode. It is where positively charged ions gain electrons in reduction reactions. It is the electrode where hydrogen is produced if the metal in the electrolyte is more reactive than hydrogen. Electrode: A solid conductive material through which electricity can flow. They are used in electrolysis to conduct electricity. Electrolysis: The splitting up of an ionic compound using electricity. The electric current is passed through a substance causing chemical reactions at the electrodes which lead to the decomposition of the materials. Electrolyte: A solution containing free ions from the molten or aqueous ionic substance. The ions are free to move to carry charge. Indicators: A chemical used in a titration reaction to identify the end point of the reaction by a clear colour change. Examples include phenolphthalein and methyl orange. Neutralisation: The reaction in which an acid and a base react to form a salt and water. https://bit.ly/pmt-cc https://bit.ly/pmt-cc Oxidation: A reaction involving the gain of oxygen. Oxidation is the loss of electrons. pH scale: A measure of the acidity or alkalinity of a solution. The scale ranges from 0-14 and can be measured using universal indicator or a pH probe. Reduction: A reaction involving the loss of oxygen. Reduction is the gain of electrons. Strong acid: An acid which is completely ionised in an aqueous solution so that nearly all the H+ ions are released. Examples of strong acids include hydrochloric, nitric and sulfuric acids. Titration: A technique used where a solution of known concentration is used to determine the concentration of an unknown solution. Universal indicator: A mixture of dyes that changes colour gradually over a range of pH and is used in testing for acids and alkalis. Weak acid: An acid which is only partially ionised in an aqueous solution. This means only a small number of the H+ ions are released. Examples of weak acids include ethanoic, citric and carbonic acids. https://bit.ly/pmt-cc https://bit.ly/pmt-cc Topic 4 - Extracting Metals and Equilibria Bacterial extraction: A method of metal extraction which uses bacteria to extract metals from their ores. The bacteria breaks down low-grade ores to produce an acidic solution containing metal ions. Cation: A positively charged ion. Metals tend to form cations. Formed when an atom loses at least one electron. Displacement: A chemical reaction in which a more reactive element displaces a less reactive element from its compound. Dynamic equilibrium: A reversible reaction will reach dynamic equilibrium when the rate of the forward reaction is equal to the rate of the backward reaction. At dynamic equilibrium, the concentration of reactants and products remains constant. Electrolysis: The splitting up of an ionic compound using electricity. The electric current is passed through a substance causing chemical reactions at the electrodes which leads to the decomposition of the materials. Electrolysis is used for metal extraction if the metal is more reactive than carbon. Haber process: An industrial process which produces ammonia from the reaction between nitrogen and hydrogen. The reaction conditions are 450oC and 200 atm and it requires an iron catalyst. Life-cycle assessment: The analysis of the impact a product has on the environment. It considers the raw materials, manufacturing, packaging, transportation, product use and disposal. Ore: A type of rock which contains metal compounds. The metals or metal compounds are present in sufficient amounts to make it worth extracting them. Oxidation: A reaction involving the gain of oxygen. Oxidation is the loss of electrons. https://bit.ly/pmt-cc https://bit.ly/pmt-cc Phytoextraction: A method of metal extraction which uses plants to absorb the metal compounds through their roots. The plants are then burned so that the metal compound can be removed from the ash. Reactivity series: A series in which metals are arranged in order of their reactivity. This can be used to predict products from reactions. Redox reaction: A reaction in which both oxidation and reduction occur simultaneously. Reduction: A reaction involving the loss of oxygen. Reduction is the gain of electrons. Reduction with carbon: Process used to extract metals from their oxides when the metal is less reactive than carbon. The metal oxide is heated with carbon so that carbon reduces the metal oxide to the metallic element. Reversible reaction: A reaction in which the products can react together to reform the reactants. Reversible reactions are denoted by the symbol ⇌. https://bit.ly/pmt-cc https://bit.ly/pmt-cc Topic 5 - Separate Chemistry 1 *Actual yield: The mass of product obtained from a reaction. It is normally less than the theoretical yield due to incomplete reactions, side reactions and loss of product in transfer. *Alloys: A metal compound made by combining two or more metals together. This process is carried out to give the material greater strength or resistance to corrosion. *Atom economy: The measure of the amount of starting materials that end up as useful products. *Avogadro’s Law: Equal volumes of different gases will contain the same number of molecules. *By-product: A secondary product made in the reaction of something else. *Chemical cell: A cell which converts chemical energy to electrical energy. They are made up of two metal electrodes connected by an electrolyte. The cell produces a voltage until one of the reactants is used up. *Corrosion: The destruction of materials by chemical reactions with substances in the environment. For example, iron rusts when exposed to water and oxygen. *Dynamic equilibrium: Reached by a reversible reaction when the rate of the forward reaction is equal to the rate of the backward reaction. At dynamic equilibrium, the concentration of reactants and products remains constant. *Electroplating: The process of coating a metal with a thin layer of another metal by electrolysis to improve the metal's corrosion resistance or to improve the metal’s https://bit.ly/pmt-cc https://bit.ly/pmt-cc appearance. *Fertiliser: A chemical added to soil to increase the fertility, allowing crops to grow more effectively. They generally contain compounds of nitrogen, potassium and phosphorus. *Fuel cell: An electrochemical cell which continuously produces a voltage when supplied with a fuel and oxygen. The fuel donates electrons at one electrode and oxygen gains electrons at the other electrode. *Haber process: An industrial process which produces ammonia from the reaction between nitrogen and hydrogen. The reaction conditions are 450oC and 200 atm and it requires an iron catalyst. *Hydrogen-oxygen fuel cell: A fuel cell in which hydrogen and oxygen are the reactants used to produce a voltage. Water is the only product. The overall reaction for the hydrogen-oxygen fuel cell is: 2H2 + O2 → 2H2O *Molar volume: The volume occupied by one mole of gaseous molecules. *Molar volume at RTP: The volume occupied by one mole of molecules of any gas at room temperature and pressure. The molar volume at RTP is 24 dm3. *Percentage yield: The percentage ratio of the actual yield of product from a reaction compared with the theoretical yield. *Sacrificial protection: The protection of iron or steel against corrosion by using a more reactive metal. Zinc is often used as a sacrificial metal. *Theoretical yield: The maximum possible mass of product that can be obtained from a reaction. *Titration: A technique used where a solution of known concentration is used to determine the concentration of an unknown solution. *Transition metal: A metal found between Group 2 and 3 of the periodic table. Typical properties include high melting points, high densities, form coloured compounds and catalytic activity. https://bit.ly/pmt-cc https://bit.ly/pmt-cc Topic 6 - Groups in the Periodic Table Alkali metals: The elements in Group 1 of the periodic table. They are typically soft and have relatively low melting points. Displacement: A chemical reaction in which a more reactive element displaces a less reactive element from its compound. Halides: The ions formed by halogen atoms when they gain an electron. They have a 1charge. E.g. Cl-, Br- and I-. Halogens: The elements in Group 7 of the periodic table. The halogens gain an electron to form halide ions with a 1- charge. Down the group the halogens get more reactive and have higher melting and boiling points. Inert: Unreactive. Noble gases are inert due to their stable electron configuration. Noble gases: The elements in Group 0 of the periodic table. They have a stable full outer shell of electrons which makes them very unreactive. Oxidation: A reaction involving the gain of oxygen. Oxidation is the loss of electrons. Reactivity series: A series in which metals are arranged in order of their reactivity. This can be used to predict products from reactions. Redox reaction: A reaction in which both oxidation and reduction occur simultaneously. Reduction: A reaction involving the loss of oxygen. Reduction is the gain of electrons. https://bit.ly/pmt-cc https://bit.ly/pmt-cc Topic 7 - Rates of Reaction and Energy Changes Activation energy: The minimum amount of energy that particles must collide with to react. Catalyst: Increase the rate of reaction by providing a different pathway for the reaction that has a lower activation energy. They are not used up during the reaction. Collision theory: Chemical reactions only occur when colliding particles collide with the correct orientation and with sufficient energy. Displacement: A chemical reaction in which a more reactive element displaces a less reactive element from its compound. Effect of concentration on reaction rate: Increasing the concentration of reactants in solution means the reacting particles will be closer together. This means they will collide more often so there will be a higher rate of successful collisions and a faster rate of reaction. Effect of pressure on reaction rate: Increasing the pressure of gaseous reactants means the reacting particles will be closer together. This means they will collide more often so there will be a higher rate of successful collisions and a faster rate of reaction. Effect of surface area on reaction rate: Increasing the surface area of the reactants means there are more exposed reacting particles. This means there are more frequent successful collisions so the rate of reaction increases. Effect of temperature on reaction rate: Increasing the temperature means the particles will have more kinetic energy and so will move faster. If the molecules are moving faster they will collide more often and, since they’ve gained kinetic energy, a larger proportion of the particles will have at least the activation energy. For both these reasons the rate of reaction increases. https://bit.ly/pmt-cc https://bit.ly/pmt-cc Endothermic reaction: A reaction that takes in energy from the surroundings so the temperature of the surroundings decreases. In an endothermic reaction, the energy needed to break existing bonds is greater than the energy released from forming new bonds. Enzymes: Biological catalysts which speed up biochemical reactions so that organisms can survive. They are used in the production of alcoholic drinks. Exothermic reaction: A reaction that transfers energy to the surroundings so the temperature of the surroundings increases. In an exothermic reaction, the energy released from forming new bonds is greater than the energy needed to break existing bonds. Neutralisation: The reaction in which an acid and a base react to form a salt and water. Overall energy change of the reaction: The difference between the sum of the energy needed to break bonds in the reactants and the sum of the energy released when bonds in the products are formed. Precipitation reaction: A reaction in which solutions react to form an insoluble product. Rate of reaction: The measure of the amount of product formed or reactant used over time. The units of rate of reaction may be given as g/s, cm3/s or mol/s. Reaction profile: Graphs used to show the relative energies of reactants and products, the activation energy and the overall energy change of a reaction. https://bit.ly/pmt-cc https://bit.ly/pmt-cc Topic 8 - Fuels and Earth Science Acid rain: Rain that is acidic due to gases, such as sulfur dioxide, reacting with water vapour in the clouds. Sulfur dioxide is produced from the burning of fossil fuels which contain sulfur impurities. Alkanes: The most common hydrocarbon found in crude oil. Alkanes have the general formula CnH2n+2. Alkenes: Alkenes are hydrocarbons with a double bond between two of the carbon atoms in their chain, causing them to be unsaturated. They have the general formula CnH2n. Catalytic cracking: Long-chain hydrocarbons are heated to turn them into a gas. The vapour is then passed over a hot powdered aluminium oxide catalyst. The long chain molecules split apart on the surface of the catalyst. Climate change: A change in global climate patterns largely believed to be caused by the increase in concentration of carbon dioxide in the atmosphere. Combustion: The burning of a substance in oxygen causing energy to be transferred to the surroundings as heat and light. During combustion, the carbon and hydrogen in the fuels are oxidised. Complete combustion: Combustion carried out in sufficient oxygen. Water and carbon dioxide are the only products of the complete combustion of a hydrocarbon. Cracking: A process that involves breaking down larger hydrocarbons to produce smaller more useful molecules. Cracking can be done by catalytic cracking or steam cracking. Crude oil: A finite resource found in rocks. It is the remains of an ancient biomass consisting mainly of plankton that was buried in mud. Most of the compounds in crude oil are hydrocarbons. https://bit.ly/pmt-cc https://bit.ly/pmt-cc Finite resource: A resource which will one day run out. Fossil fuel: Natural fuels, such as coal and gas, formed in the past from the remains of living organisms. Fractional distillation: A process used to separate a mixture of liquids. The liquids have different boiling points so can be separated into different fractions within a fractionating column. General formula: A chemical formula which applies to a class of compounds, representing the composition of the atoms present in the compound. For example, alkanes have the general formula CnH2n+2 where n is the number of carbon atoms in the molecule. Greenhouse effect: The increase in the temperature of the Earth’s atmosphere due to the greenhouse gases in the atmosphere trapping infra-red radiation from the surface. Greenhouse gases: Gases in the atmosphere which maintain temperatures on Earth high enough to support life. Greenhouse gases include water vapour, carbon dioxide and methane. Homologous series: A series of compounds with the same functional group and similar chemical properties. Hydrocarbons: Molecules that are made up of hydrogen and carbon atoms only. Incomplete combustion: Combustion which is carried out with insufficient oxygen. It can lead to the production of toxic carbon monoxide and carbon particulates. Non-renewable energy: An energy resource which is finite. Methane, petrol and diesel oil are all examples of non-renewable fossil fuels. Particulates: Polluting particles which cause global dimming and health problems for humans. Carbon particulates (soot) are a product of incomplete combustion. Photosynthesis: A reaction which occurs in plants and algae which led to the production of oxygen in the early atmosphere. This simultaneously decreased the amount of carbon dioxide in the early atmosphere. Equation for photosynthesis: 6CO2 + 6H2O → C6H12O6 + 6O2. Pollutants: A substance introduced into the environment that has undesired effects. Steam cracking: Long-chain hydrocarbons are heated to turn them into a gas. The hydrocarbon vapour is then mixed with steam and heated to a very high temperature which caused them to split into smaller molecules. https://bit.ly/pmt-cc https://bit.ly/pmt-cc Topic 9 - Separate Chemistry 2 *Addition polymerisation: The reaction in which many small molecule monomers bond together to form a long chain polymer. *Addition reaction: A reaction in which at least two molecules combine together to form a larger molecule. *Alcohols: Organic compounds containing the functional group –OH. The first four members of a homologous series of alcohols are methanol, ethanol, propanol and butanol. Alcohols can be oxidised to carboxylic acids and dehydrated to alkenes. *Biodegradable: Able to be broken down by living organisms. *Carboxylic acids: Organic compounds containing the functional group –COOH. The first four members of a homologous series of carboxylic acids are methanoic acid, ethanoic acid, propanoic acid and butanoic acid. Carboxylic acids have typical acidic properties. *Complete combustion: Combustion carried out in sufficient oxygen. Water and carbon dioxide are the only products of the complete combustion of a hydrocarbon. *Condensation polymerisation: Reactions in which monomers join together and lose small molecules, such as water. These reactions involve monomers with two functional groups. *DNA: Molecule which encodes genetic instructions for the development and functioning of living organisms and viruses. Most DNA molecules are two polymer chains, made from four different nucleotides, in the form of a double helix. *Ester: The product of a condensation reaction between a carboxylic acid and alcohol. For example: ethanol + ethanoic acid → ethyl ethanoate. https://bit.ly/pmt-cc https://bit.ly/pmt-cc *Fermentation: A chemical process by which molecules such as glucose are broken down anaerobically. Ethanol is produced when sugar solutions are fermented using yeast. *Flame photometer: A device used in flame photometry to identify the concentration of metal ions in a sample. *Flame photometry: An instrumental method used to analyse metal ions in solutions. The sample is put into a flame and the light given out is passed through a photometer. The output is a line spectrum that can be analysed to identify the metal ions in the solution and measure their concentrations. *Flame test: Qualitative test used to identify metal ions (cations). Carried out by inserting a nichrome wire loop with the unknown compound on into a flame and observing the colour. *Fractional distillation: A process used to separate a mixture of liquids. A solution of ethanol can be obtained from a fermentation mixture by fractional distillation. *Functional group: The group of atoms responsible for how a particular compound reacts. All compounds in the same homologous series have the same functional group. *Homologous series: A series of compounds with the same functional group and similar chemical properties. *Hydrocarbons: Molecules that are made up of hydrogen and carbon atoms only. *Instrumental methods: Methods used to detect and identify elements and compounds. They are accurate, sensitive and rapid. *Monomer: Small short chain molecules which can join together to form a long chain polymer. *Nanoparticles: Particles with diameters between 1 nm to 100 nm in size. Nanoparticles can exhibit properties different to those for the same material in bulk. *Nucleotides: The monomers which make up DNA. *Polyester: A category of polymers which contain the ester functional group in their main chain. Formed by a condensation reaction between a diol and a dicarboxylic acid. *Polymer: Large long-chain molecules made up of lots of small monomers joined together by covalent bonds. *Proteins: Polymers made up of amino acid molecules. *Qualitative analysis: Identification of the elements, ions or functional groups present in a compound. https://bit.ly/pmt-cc https://bit.ly/pmt-cc *Repeating unit: The part of a polymer whose repetition would produce the complete polymer chain. *Saturated hydrocarbon: A hydrocarbon compound containing only single bonds between carbon atoms. Alkanes are saturated compounds. *Starch: A polymer based on sugars. *Unsaturated hydrocarbon: A compound that contains double or triple carbon bonds so that it does not contain the maximum number of hydrogen atoms. Alkenes are unsaturated compounds. https://bit.ly/pmt-cc https://bit.ly/pmt-cc
