Fifths iGCSE Keywords to Learn PDF

Fifths iGCSE keywords to learn Topic Keyword - definition Learnt Energetics, Activation energy - The minimum amount of energy required for a collision to be successful....

Fifths iGCSE keywords to learn Topic Keyword - definition Learnt Energetics, Activation energy - The minimum amount of energy required for a collision to be successful. equilibrium Endothermic - Reactions in which heat energy is taken in from the surroundings. and rates: Enthalpy change - The amount of heat energy taken in or given out in a chemical reaction (ΔH). Exothermic - Reactions in which heat energy is given out to the surroundings. Bond energy - The amount of energy required to break 1 mole of covalent bonds in gaseous molecules, or the amount of energy released when 1 mole of covalent bonds are formed in gaseous molecules. Collision theory - States that for a reaction to occur, the reactant particles must collide with each other and the collision needs to have sufficient energy and the correct orientation. Rate - The speed at which the amount of reactants decreases or the amount of products increases. It is measured as a change in the concentration (or amount) of reactants or products per unit time. Successful collisions - Collisions with energy greater than or equal to the activation energy. Dynamic equilibrium - Equilibrium means the concentrations of the reactants and the products in a reversible reaction remain constant. Dynamic means the rate of the forward reaction is equal to the rate of the reverse reaction. Hydrocarbons: Alkanes - Saturated hydrocarbons (joined with single covalent bonds) with the general formula CnH2n+2. Alkenes - These are unsaturated hydrocarbons (which contain a carbon–carbon double bond) with the general formula CnH2n. Cracking - A process in which long-chain alkanes are converted to alkenes and shorter-chain alkanes. Crude oil - A mixture of hydrocarbons formed from the remains of living organisms when their soft tissue was gradually changed by high temperatures and pressures into a thick, black oil. Fractional distillation - A process to separate two liquids of similar boiling points. Fractionating column - A piece of equipment used for separating vapours in fractional distillation. Thermal decomposition - breaking down of a substance due to heat. Unsaturated - Compounds that contain one or more carbon–carbon double or triple bonds. Viscous - A liquid that is resistant to flow. Volatile - A substance that evaporates easily. Global warming - Greenhouse gases, including carbon dioxide, trap the heat radiated from the Earth’s surface (originally from the Sun) and lead to an increase in the temperature of the Earth and its atmosphere.  Biofuel - A fuel that is made from biological sources, such as sugar cane or corn. Hydrocarbon - Molecules containing carbon and hydrogen only. Saturated compound - A compound containing only carbon–carbon single bonds with no carbon–carbon double or triple bonds. Bonding: Covalent bonding - Strong electrostatic force of attraction between the nuclei of the atoms making up the bond and the shared pair of electrons. Metallic bonding - Electrostatic force of attraction between a lattice of positive ions and the sea of delocalised electrons. Intermolecular force - Force of attraction between covalent molecules, much weaker than covalent bonds within the molecules. Ion - Charged particle formed when an atom (or group of atoms) loses or gains electrons. Ionic bonding - Strong electrostatic force of attraction between oppositely charged ions. Double bond - Atoms sharing two pairs of electrons in a covalent bond. Element - A substance that cannot be split into anything simpler by chemical means. Giant ionic lattice - The arrangement of ions in an ionic compound in its solid state. Electrolysis Anion - A negative ion, formed by atoms gaining electrons. and redox: Anode - The positive electrode in electrolysis, which attracts negative anions. Cathode - The negative electrode in electrolysis, which attracts positive cations. Cation - A positive ion, formed by atoms losing electrons. Electrolysis - Breaking down of an ionic compound using electricity. Electrolyte - Electrolytes are molten ionic compounds or solutions containing ions. Redox - Reduction and oxidation a reaction that involves both reduction and oxidation occurring together. Oxidation - Gain of oxygen or loss of electrons. Oxidising agent - Something that oxidises something else by taking electrons away from it. An oxidising agent is reduced in a chemical reaction. Reducing agent - Something that reduces something else by giving electrons to it. A reducing agent is oxidised in a chemical reaction. Reduction - Loss of oxygen or gain of electrons. Half-equation - A balanced symbol equation to describe either oxidation or reduction. Separation Condensation - The change of state from a gas to a liquid. techniques: Crystallisation - A process in which a solute (soluble solid) is obtained from its solvent. Saturated solution - A solution that contains as much dissolved solid as possible at a particular temperature.  Solubility - The mass of solute which must dissolve in 100 g of solvent to form a saturated solution at a particular temperature. Solute - The substance that dissolves in a solvent. Solution - The mixture formed when a solute dissolves in a solvent. Solvent - The liquid that a solute dissolves in. Rf value - The retardation factor, which is calculated as the distance moved by a spot (from the pencil line) divided by the distance moved by the solvent front (from the pencil line) on a chromatogram. Evaporation - The change of state from a liquid to a vapour. Filtrate - The liquid that comes through the filter paper during filtration. Filtration - A process to separate an insoluble solid from a liquid. Freezing - The change of state from a liquid to a solid. Acids and Anhydrous - Without water. salts: Base - A substance that neutralises acids, they are usually metal oxides, hydroxides or ammonia. Alkali - A soluble base that acts as a source of hydroxide ions (OH–) in solution. Precipitate - A fine solid that is formed by a chemical reaction involving liquids or gases. Indicator - A substance that has different colours depending on the pH. Water of crystallisation - Water molecules that are part of a crystal structure in which they are chemically bound up with a salt. Represented by ·nH2O in the formulae of compounds. Atoms Compound - A substance that forms when two or more elements chemically combine. The elements cannot be separated by physical means. Mixture - Two or more substances not chemically combined that can be separated by physical means. Molecule - Two or more atoms covalently bonded together. Molecules contain a certain fixed number of atoms. Atomic number - The number of protons in an atom. Isotopes - Atoms with the same number of protons but a different number of neutrons. Isotopes have the same chemical properties. Metals: Alloy - A mixture of a metal with, usually, other metals or carbon. Displacement reaction - A chemical reaction in which a more reactive element replaces a less reactive one in its compound. Galvanisation - A method of preventing rusting by coating iron with a layer of zinc. Ore - Rocks that contain enough of the mineral for it to be worthwhile to extract the metal. Molten - Liquid state when a solid has melted.  Sacrificial protection - A method of preventing rusting by attaching a block of a more reactive metal to iron. The more reactive metals undergo oxidation in preference to the iron. Scientific Anomalous result - A result that does not fit in with the pattern of the others. terminology: Dependent variable - What you measure in an experiment. Independent variable - What you vary in an experiment. Non-continuous variable - An independent variable which can only take certain values. Non-renewable resource - A finite resource that cannot be replaced, at least not for millions of years. Tangent - A straight line that touches a curve, but does not cut across it. Group - A vertical column in the Periodic Table. All elements in the same group have the same number of outer shell electrons. Aqueous - Something dissolved in water. Diatomic - A molecule that contains two atoms. Inert - Unreactive. Definition Command word Understand? Add/label Requires the addition or labelling of a stimulus material given in the question, for example labelling a diagram or adding units to a table. Calculate Obtain a numerical answer, showing relevant working. Comment on Requires the synthesis of a number of variables from data/information to form a judgement. Complete Requires the completion of a table/diagram. Deduce Draw/reach conclusion(s) from the information provided. Describe Give an account of something. Statements in the response need to be developed, as they are often linked, but do not need to include a justification or reason. Design Plan or invent a procedure from existing principles/ideas. Determine The answer must have an element that is quantitative from the stimulus provided, or must show how the answer can be reached quantitatively. To gain maximum marks, there must be a quantitative element to the answer. ◾ Identify the issue/situation/problem/ argument that is being assessed within the question. ◾ Explore all aspects of an issue/ situation/problem/ argument. Discuss ◾ Investigate the issue/situation etc. by reasoning or argument. Draw Produce a diagram either using a ruler or freehand. Estimate Find an approximate value, number or quantity from a diagram/given data or through a calculation. Evaluate Review information (e.g. data, methods) then bring it together to form a conclusion, drawing on evidence including strengths, weaknesses, alternative actions, relevant data or information. Come to a supported judgement of a subject’s quality and relate it to its context.  Explain An explanation requires a justification/ exemplification of a point. The answer must contain some element of reasoning/justification, which can include mathematical explanations. Give/state/name All of these command words are really synonyms. They generally all require recall of one or more pieces of information. Give a reason / When a statement has been made and the requirement is only to give the reason(s) why. reasons Identify Usually requires some key information to be selected from a given stimulus/ resource. Justify Give evidence to support (either the statement given in the question or an earlier answer). Plot Produce a graph by marking points accurately on a grid from data that is provided and then draw a line of best fit through these points. A suitable scale and appropriately labelled axes must be included if these are not provided in the question. Predict Give an expected result. Show that Verify the statement given in the question. Sketch Produce a freehand drawing. For a graph, this would need a line and labelled axes with important features indicated. The axes are not scaled. State what is When the meaning of a term is expected but there are different ways for how these can be described. meant by Suggest Use your knowledge to propose a solution to a problem in a novel context.