Solution. An indicator is a substance that has more than one colour form depending on the pH.Universal indicator is a mixture of different dyes which change colour. You then use the pH chart to find out whether your substance is alkali(ne) or acid. For use as laboratory reagent. The common application of indicators is the detection of end points of titrations. Universal Indicator. magnesium, zinc and iron), 2:22 (Triple only) know that most metals are extracted from ores found in the Earth’s crust and that unreactive metals are often found as the uncombined element, 2:23 (Triple only) explain how the method of extraction of a metal is related to its position in the reactivity series, illustrated by carbon extraction for iron and electrolysis for aluminium, 2:24 (Triple only) be able to comment on a metal extraction process, given appropriate information, 2:25 (Triple only) explain the uses of aluminium, copper, iron and steel in terms of their properties the types of steel will be limited to low-carbon (mild), high-carbon and stainless, 2:26 (Triple only) know that an alloy is a mixture of a metal and one or more elements, usually other metals or carbon, 2:27 (Triple only) explain why alloys are harder than pure metals, 2:28 describe the use of litmus, phenolphthalein and methyl orange to distinguish between acidic and alkaline solutions, 2:29 understand how to use the pH scale, from 0–14, can be used to classify solutions as strongly acidic (0–3), weakly acidic (4–6), neutral (7), weakly alkaline (8–10) and strongly alkaline (11–14), 2:30 describe the use of Universal Indicator to measure the approximate pH value of an aqueous solution, 2:31 know that acids in aqueous solution are a source of hydrogen ions and alkalis in a aqueous solution are a source of hydroxide ions, 2:32 know that bases can neutralise acids, 2:33 (Triple only) describe how to carry out an acid-alkali titration, 2:34 know the general rules for predicting the solubility of ionic compounds in water: common sodium, potassium and ammonium compounds are soluble, all nitrates are soluble, common chlorides are soluble, except those of silver and lead(II), common sulfates are soluble, except for those of barium, calcium and lead(II), common carbonates are insoluble, except for those of sodium, potassium and ammonium, common hydroxides are insoluble except for those of sodium, potassium and calcium (calcium hydroxide is slightly soluble), 2:35 understand acids and bases in terms of proton transfer, 2:36 understand that an acid is a proton donor and a base is a proton acceptor, 2:37 describe the reactions of hydrochloric acid, sulfuric acid and nitric acid with metals, bases and metal carbonates (excluding the reactions between nitric acid and metals) to form salts, 2:38 know that metal oxides, metal hydroxides and ammonia can act as bases, and that alkalis are bases that are soluble in water, 2:39 describe an experiment to prepare a pure, dry sample of a soluble salt, starting from an insoluble reactant, 2:40 (Triple only) describe an experiment to prepare a pure, dry sample of a soluble salt, starting from an acid and alkali, 2:41 (Triple only) describe an experiment to prepare a pure, dry sample of an insoluble salt, starting from two soluble reactants, 2:42 practical: prepare a sample of pure, dry hydrated copper(II) sulfate crystals starting from copper(II) oxide, 2:43 (Triple only) practical: prepare a sample of pure, dry lead(II) sulfate, 2:44a describe tests for these gases: hydrogen, carbon dioxide, 2:44 describe tests for these gases: hydrogen, oxygen, carbon dioxide, ammonia, chlorine, 2:45 describe how to carry out a flame test, 2:46 know the colours formed in flame tests for these cations: Li⁺ is red, Na⁺ is yellow, K⁺ is lilac, Ca²⁺ is orange-red, Cu²⁺ is blue-green, 2:47 describe tests for these cations: NH₄⁺ using sodium hydroxide solution and identifying the gas evolved, Cu²⁺, Fe²⁺ and Fe³⁺ using sodium hydroxide solution, 2:48 describe tests for these anions: Cl⁻, Br⁻ and I⁻ using acidified silver nitrate solution, SO₄²⁻ using acidified barium chloride solution, CO₃²⁻ using hydrochloric acid and identifying the gas evolved, 2:49 describe a test for the presence of water using anhydrous copper(II) sulfate, 2:50 describe a physical test to show whether a sample of water is pure, 3:01 know that chemical reactions in which heat energy is given out are described as exothermic, and those in which heat energy is taken in are described as endothermic, 3:02 describe simple calorimetry experiments for reactions such as combustion, displacement, dissolving and neutralisation, 3:03 calculate the heat energy change from a measured temperature change using the expression Q = mcΔT, 3:04 calculate the molar enthalpy change (ΔH) from the heat energy change, Q, 3:05 (Triple only) draw and explain energy level diagrams to represent exothermic and endothermic reactions, 3:06 (Triple only) know that bond-breaking is an endothermic process and that bond-making is an exothermic process, 3:07 (Triple only) use bond energies to calculate the enthalpy change during a chemical reaction, 3:08 practical: investigate temperature changes accompanying some of the following types of change: salts dissolving in water, neutralisation reactions, displacement reactions and combustion reactions, 3:09 describe experiments to investigate the effects of changes in surface area of a solid, concentration of a solution, temperature and the use of a catalyst on the rate of a reaction, 3:10 describe the effects of changes in surface area of a solid, concentration of a solution, pressure of a gas, temperature and the use of a catalyst on the rate of a reaction, 3:11 explain the effects of changes in surface area of a solid, concentration of a solution, pressure of a gas and temperature on the rate of a reaction in terms of particle collision theory, 3:12 know that a catalyst is a substance that increases the rate of a reaction, but is chemically unchanged at the end of the reaction, 3:13 know that a catalyst works by providing an alternative pathway with lower activation energy, 3:14 (Triple only) draw and explain reaction profile diagrams showing ΔH and activation energy, 3:15 practical: investigate the effect of changing the surface area of marble chips and of changing the concentration of hydrochloric acid on the rate of reaction between marble chips and dilute hydrochloric acid, 3:16 practical: investigate the effect of different solids on the catalytic decomposition of hydrogen peroxide solution, 3:17 know that some reactions are reversible and this is indicated by the symbol ⇌ in equations, 3:18 describe reversible reactions such as the dehydration of hydrated copper(II) sulfate and the effect of heat on ammonium chloride, 3:19 (Triple only) know that a reversible reaction can reach dynamic equilibrium in a sealed container, 3:20 (Triple only) know that the characteristics of a reaction at dynamic equilibrium are: the forward and reverse reactions occur at the same rate, and the concentrations of reactants and products remain constant, 3:21 (Triple only) understand why a catalyst does not affect the position of equilibrium in a reversible reaction, 3:22 (Triple only) predict, with reasons, the effect of changing either pressure or temperature on the position of equilibrium in a reversible reaction (references to Le Chatelier’s principle are not required), 4:01 know that a hydrocarbon is a compound of hydrogen and carbon only, 4:02 understand how to represent organic molecules using empirical formulae, molecular formulae, general formulae, structural formulae and displayed formulae, 4:03a know what is meant by the term isomerism, 4:03 know what is meant by the terms homologous series, functional group and isomerism, 4:04 understand how to name compounds relevant to this specification using the rules of International Union of Pure and Applied Chemistry (IUPAC) nomenclature. 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