{"id":12471,"date":"2026-10-03T08:32:12","date_gmt":"2026-10-03T07:32:12","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-12-entropy-and-energetics\/"},"modified":"2026-10-03T08:35:11","modified_gmt":"2026-10-03T07:35:11","slug":"topic-12-entropy-and-energetics","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-12-entropy-and-energetics\/","title":{"rendered":"Topic 12 Entropy and Energetics"},"content":{"rendered":"\n<div class=\"ols-t12-page\">\n\n  <aside class=\"ols-sidebar\">\n  <div class=\"ols-sidebar-header\">\n    <h3>Revision Notes<\/h3>\n    <p>A Level Chemistry<\/p>\n  <\/div>\n\n  <div class=\"ols-topic-group\">\n    <h4>Topic 12 Entropy and Energetics<\/h4>\n\n    <ul class=\"ols-topic-list\">\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-12-entropy-and-energetics\/\">Topic 12 Entropy and Energetics Overview<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-12-entropy-and-energetics\/entropy-and-the-direction-of-change\/\">Entropy and the Direction of Change<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-12-entropy-and-energetics\/calculating-entropy-changes\/\">Calculating Entropy Changes<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-12-entropy-and-energetics\/feasibility-gibbs-energy-and-temperature\/\">Feasibility and Temperature<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-12-entropy-and-energetics\/thermodynamic-and-kinetic-stability\/\">Thermodynamic and Kinetic Stability<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-12-entropy-and-energetics\/lattice-energy-and-born-haber-cycles\/\">Lattice Energy and Born\u2013Haber Cycles<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-12-entropy-and-energetics\/lattice-energy-trends-and-covalent-character\/\">Lattice Energy Trends and Covalent Character<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-12-entropy-and-energetics\/enthalpy-of-solution-and-hydration\/\">Enthalpy of Solution and Hydration<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-12-entropy-and-energetics\/predicting-solubility\/\">Predicting Solubility<\/a>\n      <\/li>\n    <\/ul>\n  <\/div>\n\n  <div class=\"ols-topic-group\">\n    <h4>Other Sections<\/h4>\n\n    <ul class=\"ols-topic-list\">\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-6-energetics\/\">Topic 6 Energetics (AS)<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-11-kinetics\/\">Topic 11 Kinetics<\/a>\n      <\/li>\n      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{ background: radial-gradient(circle at 24% 18%, rgba(255,255,255,0.46), transparent 24%), linear-gradient(135deg, #ecfeff 0%, #22d3ee 45%, #0e7490 100%); }\n    .ols-t12-visual--ei { background: radial-gradient(circle at 24% 18%, rgba(255,255,255,0.46), transparent 24%), linear-gradient(135deg, #f5f3ff 0%, #a78bfa 45%, #5b21b6 100%); }\n    .ols-t12-visual--kc { background: radial-gradient(circle at 24% 18%, rgba(255,255,255,0.46), transparent 24%), linear-gradient(135deg, #f0fdf4 0%, #4ade80 45%, #166534 100%); }\n  <\/style>\n\n  <!-- BREADCRUMB BAR - sits above everything -->\n  <div class=\"ols-t12-breadcrumb-bar\">\n    <div class=\"ols-t12-container\">\n      <nav class=\"ols-t12-breadcrumb\" aria-label=\"Breadcrumb\">\n          <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/\">Revision Notes<\/a> \/\n          <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/\">A Level Chemistry<\/a> \/\n          <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/\">Edexcel International<\/a> \/\n          <span>Topic 12 Entropy and Energetics<\/span>\n        <\/nav>\n    <\/div>\n  <\/div>\n\n  <!-- INTRO -->\n  <section class=\"ols-t12-intro\">\n    <div class=\"ols-t12-container\">\n      <div class=\"ols-t12-intro-inner\">\n        <div>\n          <div class=\"ols-t12-eyebrow\">Edexcel International A Level Chemistry<\/div>\n          <h1>Topic 12<br>Entropy and<br>Energetics<\/h1>\n          <div class=\"ols-t12-accent-bar\"><\/div>\n          <p class=\"ols-t12-intro-lead\">Topic 12 explains why reactions happen. It builds entropy as the measure of disorder and the dispersal of energy, calculates the entropy changes of the system, the surroundings and the total, uses them to decide feasibility and the temperature at which a reaction becomes feasible, separates thermodynamic from kinetic stability, then turns to ionic solids: lattice energy and Born\u2013Haber cycles, covalent character and polarisation, enthalpies of solution and hydration, and predicting solubility. It is examined in Unit 4.<\/p>\n        <\/div>\n        <div class=\"ols-t12-info-grid\">\n          <div class=\"ols-t12-info-card\"><div class=\"ols-t12-info-card-label\">Exam Unit<\/div><div class=\"ols-t12-info-card-value\">Unit 4<\/div><div class=\"ols-t12-info-card-sub\">WCH14\/01 &#8211; IAL<\/div><\/div>\n          <div class=\"ols-t12-info-card\"><div class=\"ols-t12-info-card-label\">Specification Points<\/div><div class=\"ols-t12-info-card-value\">12.1 &#8211; 12.19<\/div><div class=\"ols-t12-info-card-sub\">19 points covered<\/div><\/div>\n          <div class=\"ols-t12-info-card\"><div class=\"ols-t12-info-card-label\">Topic Parts<\/div><div class=\"ols-t12-info-card-value\">8 pages<\/div><div class=\"ols-t12-info-card-sub\">Revision notes available<\/div><\/div>\n          <div class=\"ols-t12-info-card\"><div class=\"ols-t12-info-card-label\">Exam Board<\/div><div class=\"ols-t12-info-card-value\">Edexcel IAL<\/div><div class=\"ols-t12-info-card-sub\">Pearson International<\/div><\/div>\n        <\/div>\n      <\/div>\n    <\/div>\n  <\/section>\n\n  <!-- TOPIC CARDS -->\n  <section class=\"ols-t12-topics\">\n    <div class=\"ols-t12-container\">\n\n      <div class=\"ols-t12-section-header\">\n        <h2 class=\"ols-t12-section-title\">Revision Notes<\/h2>\n      <\/div>\n\n      <div class=\"ols-t12-cards-grid\">\n\n        <!-- Card 1: Entropy and the Direction of Change -->\n        <a class=\"ols-t12-card ols-t12-card--available\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-12-entropy-and-energetics\/entropy-and-the-direction-of-change\/\">\n          <div class=\"ols-t12-card-img-wrap\">\n            <div class=\"ols-t12-visual ols-t12-visual--ox\">\n              <div class=\"ols-t12-visual-panel\">\n                <div class=\"ols-t12-visual-kicker\">Disorder and dispersal<\/div>\n                <div class=\"ols-t12-visual-main\">Entropy<\/div>\n                <div class=\"ols-t12-visual-sub\">S rises: solid, liquid, gas<\/div>\n              <\/div>\n            <\/div>\n            <div class=\"ols-t12-card-num\">1<\/div>\n            <span class=\"ols-t12-card-status ols-t12-card-status--available\">Available<\/span>\n          <\/div>\n          <div class=\"ols-t12-card-body\">\n            <p class=\"ols-t12-card-title\">Entropy and the Direction of Change<\/p>\n            <p class=\"ols-t12-card-desc\">Entropy: disorder and the dispersal of energy, entropy and temperature, changes of state, dissolving, gas moles and the natural direction of change.<\/p>\n            <span class=\"ols-t12-card-cta\">Start revising<svg viewBox=\"0 0 16 16\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\"><path d=\"M3 8h10M9 4l4 4-4 4\"><\/path><\/svg><\/span>\n          <\/div>\n        <\/a>\n\n        <!-- Card 2: Calculating Entropy Changes -->\n        <a class=\"ols-t12-card ols-t12-card--available\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-12-entropy-and-energetics\/calculating-entropy-changes\/\">\n          <div class=\"ols-t12-card-img-wrap\">\n            <div class=\"ols-t12-visual ols-t12-visual--tc\">\n              <div class=\"ols-t12-visual-panel\">\n                <div class=\"ols-t12-visual-kicker\">\u03a3S(products) \u2212 \u03a3S(reactants)<\/div>\n                <div class=\"ols-t12-visual-main\">Entropy<br>Calculations<\/div>\n                <div class=\"ols-t12-visual-sub\">system, surroundings, total<\/div>\n              <\/div>\n            <\/div>\n            <div class=\"ols-t12-card-num\">2<\/div>\n            <span class=\"ols-t12-card-status ols-t12-card-status--available\">Available<\/span>\n          <\/div>\n          <div class=\"ols-t12-card-body\">\n            <p class=\"ols-t12-card-title\">Calculating Entropy Changes<\/p>\n            <p class=\"ols-t12-card-desc\">Entropy calculations: \u0394S from standard entropies, \u0394S of the surroundings from \u2212\u0394H\/T and the total entropy change.<\/p>\n            <span class=\"ols-t12-card-cta\">Start revising<svg viewBox=\"0 0 16 16\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\"><path d=\"M3 8h10M9 4l4 4-4 4\"><\/path><\/svg><\/span>\n          <\/div>\n        <\/a>\n\n        <!-- Card 3: Feasibility and Temperature -->\n        <a class=\"ols-t12-card ols-t12-card--available\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-12-entropy-and-energetics\/feasibility-gibbs-energy-and-temperature\/\">\n          <div class=\"ols-t12-card-img-wrap\">\n            <div class=\"ols-t12-visual ols-t12-visual--tr\">\n              <div class=\"ols-t12-visual-panel\">\n                <div class=\"ols-t12-visual-kicker\">\u0394Stotal > 0<\/div>\n                <div class=\"ols-t12-visual-main\">Feasibility and<br>Temperature<\/div>\n                <div class=\"ols-t12-visual-sub\">T = \u0394H \u00f7 \u0394S<\/div>\n              <\/div>\n            <\/div>\n            <div class=\"ols-t12-card-num\">3<\/div>\n            <span class=\"ols-t12-card-status ols-t12-card-status--available\">Available<\/span>\n          <\/div>\n          <div class=\"ols-t12-card-body\">\n            <p class=\"ols-t12-card-title\">Feasibility and Temperature<\/p>\n            <p class=\"ols-t12-card-desc\">Feasibility: \u0394Stotal = \u0394Ssystem + \u0394Ssurroundings, the effect of temperature and the temperature at which a reaction becomes feasible.<\/p>\n            <span class=\"ols-t12-card-cta\">Start revising<svg viewBox=\"0 0 16 16\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\"><path d=\"M3 8h10M9 4l4 4-4 4\"><\/path><\/svg><\/span>\n          <\/div>\n        <\/a>\n\n        <!-- Card 4: Thermodynamic and Kinetic Stability -->\n        <a class=\"ols-t12-card ols-t12-card--available\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-12-entropy-and-energetics\/thermodynamic-and-kinetic-stability\/\">\n          <div class=\"ols-t12-card-img-wrap\">\n            <div class=\"ols-t12-visual ols-t12-visual--ca\">\n              <div class=\"ols-t12-visual-panel\">\n                <div class=\"ols-t12-visual-kicker\">Feasible is not fast<\/div>\n                <div class=\"ols-t12-visual-main\">Thermodynamic and<br>Kinetic Stability<\/div>\n                <div class=\"ols-t12-visual-sub\">\u0394G, E\u2090, diamond and petrol<\/div>\n              <\/div>\n            <\/div>\n            <div class=\"ols-t12-card-num\">4<\/div>\n            <span class=\"ols-t12-card-status ols-t12-card-status--available\">Available<\/span>\n          <\/div>\n          <div class=\"ols-t12-card-body\">\n            <p class=\"ols-t12-card-title\">Thermodynamic and Kinetic Stability<\/p>\n            <p class=\"ols-t12-card-desc\">Thermodynamic and kinetic stability: feasible but slow reactions, activation energy and the limits of \u0394G and \u0394Stotal predictions.<\/p>\n            <span class=\"ols-t12-card-cta\">Start revising<svg viewBox=\"0 0 16 16\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\"><path d=\"M3 8h10M9 4l4 4-4 4\"><\/path><\/svg><\/span>\n          <\/div>\n        <\/a>\n\n        <!-- Card 5: w => `${lattC(w)} and Born\u2013Haber Cycles` -->\n        <a class=\"ols-t12-card ols-t12-card--available\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-12-entropy-and-energetics\/lattice-energy-and-born-haber-cycles\/\">\n          <div class=\"ols-t12-card-img-wrap\">\n            <div class=\"ols-t12-visual ols-t12-visual--de\">\n              <div class=\"ols-t12-visual-panel\">\n                <div class=\"ols-t12-visual-kicker\">Hess\u2019s law for ionic solids<\/div>\n                <div class=\"ols-t12-visual-main\">Born\u2013Haber<br>Cycles<\/div>\n                <div class=\"ols-t12-visual-sub\">lattice energy, \u0394atH, electron affinity<\/div>\n              <\/div>\n            <\/div>\n            <div class=\"ols-t12-card-num\">5<\/div>\n            <span class=\"ols-t12-card-status ols-t12-card-status--available\">Available<\/span>\n          <\/div>\n          <div class=\"ols-t12-card-body\">\n            <p class=\"ols-t12-card-title\">Lattice Energy and Born\u2013Haber Cycles<\/p>\n            <p class=\"ols-t12-card-desc\">Lattice energy and Born\u2013Haber cycles: definitions of atomisation, ionisation energy and electron affinity, constructing the cycle for NaCl and MgCl\u2082 and calculating the missing value.<\/p>\n            <span class=\"ols-t12-card-cta\">Start revising<svg viewBox=\"0 0 16 16\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\"><path d=\"M3 8h10M9 4l4 4-4 4\"><\/path><\/svg><\/span>\n          <\/div>\n        <\/a>\n\n        <!-- Card 6: w => `${lattC(w)} Trends and Covalent Character` -->\n        <a class=\"ols-t12-card ols-t12-card--available\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-12-entropy-and-energetics\/lattice-energy-trends-and-covalent-character\/\">\n          <div class=\"ols-t12-card-img-wrap\">\n            <div class=\"ols-t12-visual ols-t12-visual--lc\">\n              <div class=\"ols-t12-visual-panel\">\n                <div class=\"ols-t12-visual-kicker\">Charge density<\/div>\n                <div class=\"ols-t12-visual-main\">Polarisation and<br>Covalent Character<\/div>\n                <div class=\"ols-t12-visual-sub\">theoretical against experimental<\/div>\n              <\/div>\n            <\/div>\n            <div class=\"ols-t12-card-num\">6<\/div>\n            <span class=\"ols-t12-card-status ols-t12-card-status--available\">Available<\/span>\n          <\/div>\n          <div class=\"ols-t12-card-body\">\n            <p class=\"ols-t12-card-title\">Lattice Energy Trends and Covalent Character<\/p>\n            <p class=\"ols-t12-card-desc\">Lattice energy trends: charge and radius, the perfect ionic model against Born\u2013Haber values, polarisation and covalent character in ionic compounds.<\/p>\n            <span class=\"ols-t12-card-cta\">Start revising<svg viewBox=\"0 0 16 16\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\"><path d=\"M3 8h10M9 4l4 4-4 4\"><\/path><\/svg><\/span>\n          <\/div>\n        <\/a>\n\n        <!-- Card 7: Enthalpy of Solution and Hydration -->\n        <a class=\"ols-t12-card ols-t12-card--available\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-12-entropy-and-energetics\/enthalpy-of-solution-and-hydration\/\">\n          <div class=\"ols-t12-card-img-wrap\">\n            <div class=\"ols-t12-visual ols-t12-visual--ei\">\n              <div class=\"ols-t12-visual-panel\">\n                <div class=\"ols-t12-visual-kicker\">Lattice broken, ions hydrated<\/div>\n                <div class=\"ols-t12-visual-main\">Solution and<br>Hydration<\/div>\n                <div class=\"ols-t12-visual-sub\">\u0394solH = \u2212LE + \u03a3\u0394hydH<\/div>\n              <\/div>\n            <\/div>\n            <div class=\"ols-t12-card-num\">7<\/div>\n            <span class=\"ols-t12-card-status ols-t12-card-status--available\">Available<\/span>\n          <\/div>\n          <div class=\"ols-t12-card-body\">\n            <p class=\"ols-t12-card-title\">Enthalpy of Solution and Hydration<\/p>\n            <p class=\"ols-t12-card-desc\">Enthalpy of solution and hydration: definitions, energy cycles with lattice energy, worked calculations and the effect of ionic charge and radius.<\/p>\n            <span class=\"ols-t12-card-cta\">Start revising<svg viewBox=\"0 0 16 16\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\"><path d=\"M3 8h10M9 4l4 4-4 4\"><\/path><\/svg><\/span>\n          <\/div>\n        <\/a>\n\n        <!-- Card 8: Predicting Solubility -->\n        <a class=\"ols-t12-card ols-t12-card--available\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-12-entropy-and-energetics\/predicting-solubility\/\">\n          <div class=\"ols-t12-card-img-wrap\">\n            <div class=\"ols-t12-visual ols-t12-visual--kc\">\n              <div class=\"ols-t12-visual-panel\">\n                <div class=\"ols-t12-visual-kicker\">\u0394solH and \u0394S together<\/div>\n                <div class=\"ols-t12-visual-main\">Predicting<br>Solubility<\/div>\n                <div class=\"ols-t12-visual-sub\">Group 2 hydroxides and sulfates<\/div>\n              <\/div>\n            <\/div>\n            <div class=\"ols-t12-card-num\">8<\/div>\n            <span class=\"ols-t12-card-status ols-t12-card-status--available\">Available<\/span>\n          <\/div>\n          <div class=\"ols-t12-card-body\">\n            <p class=\"ols-t12-card-title\">Predicting Solubility<\/p>\n            <p class=\"ols-t12-card-desc\">Predicting solubility from enthalpy and entropy changes of solution, with the Group 2 hydroxide and sulfate trends explained.<\/p>\n            <span class=\"ols-t12-card-cta\">Start revising<svg viewBox=\"0 0 16 16\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\" stroke-linecap=\"round\" stroke-linejoin=\"round\"><path d=\"M3 8h10M9 4l4 4-4 4\"><\/path><\/svg><\/span>\n          <\/div>\n        <\/a>\n\n      <\/div>\n    <\/div>\n  <\/section>\n\n  <!-- SPECIFICATION -->\n  <section class=\"ols-t12-spec-section\">\n    <div class=\"ols-t12-container\">\n      <div class=\"ols-t12-spec-wrap\">\n        <div class=\"ols-t12-spec-pill\">Specification Coverage<\/div>\n        <h2 class=\"ols-t12-spec-heading\">Topic 12 Entropy and Energetics &#8211; Edexcel International A Level Chemistry<\/h2>\n        <p class=\"ols-t12-spec-intro-text\">The following specification points outline the knowledge and skills students are expected to demonstrate for Topic 12. Wording follows the Pearson Edexcel International A Level Chemistry specification.<\/p>\n        <h3 class=\"ols-t12-spec-group-title\">12.1 &#8211; 12.11 Entropy, feasibility and stability<\/h3>\n        <div class=\"ols-t12-spec-rows\">\n          <div class=\"ols-t12-spec-row ols-t12-spec-row--light\"><div class=\"ols-t12-spec-code\">12.1<\/div><div class=\"ols-t12-spec-text\">understand that, since endothermic reactions can occur spontaneously at room temperature, enthalpy changes alone do not control whether reactions occur<\/div><\/div>\n          <div class=\"ols-t12-spec-row ols-t12-spec-row--mid\"><div class=\"ols-t12-spec-code ols-t12-spec-code--mid\">12.2<\/div><div class=\"ols-t12-spec-text\"><div class=\"ols-t12-spec-sub-list\"><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">a<\/div><div class=\"ols-t12-spec-sub-text\">understand entropy as a measure of disorder of a system in terms of random dispersal of molecules<\/div><\/div><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">b<\/div><div class=\"ols-t12-spec-sub-text\">understand entropy as a measure of disorder of a system in terms of random dispersal of energy quanta between molecules<\/div><\/div><\/div><\/div><\/div>\n          <div class=\"ols-t12-spec-row ols-t12-spec-row--light\"><div class=\"ols-t12-spec-code\">12.3<\/div><div class=\"ols-t12-spec-text\"><div class=\"ols-t12-spec-sub-list\"><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">a<\/div><div class=\"ols-t12-spec-sub-text\">understand that entropy of a substance increases with temperature<\/div><\/div><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">b<\/div><div class=\"ols-t12-spec-sub-text\">understand that entropy increases as solid changes to liquid<\/div><\/div><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">c<\/div><div class=\"ols-t12-spec-sub-text\">understand that entropy increases as liquid changes to gas<\/div><\/div><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">d<\/div><div class=\"ols-t12-spec-sub-text\">understand that perfect crystals at zero kelvin have zero entropy<\/div><\/div><\/div><\/div><\/div>\n          <div class=\"ols-t12-spec-row ols-t12-spec-row--mid\"><div class=\"ols-t12-spec-code ols-t12-spec-code--mid\">12.4<\/div><div class=\"ols-t12-spec-text\"><div class=\"ols-t12-spec-sub-list\"><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">a<\/div><div class=\"ols-t12-spec-sub-text\">be able to interpret the natural direction of change as the direction of increasing total entropy<\/div><\/div><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">b<\/div><div class=\"ols-t12-spec-sub-text\">be able to interpret gases spreading spontaneously through a room as an example of increasing total entropy<\/div><\/div><\/div><\/div><\/div>\n          <div class=\"ols-t12-spec-row ols-t12-spec-row--light\"><div class=\"ols-t12-spec-code\">12.5<\/div><div class=\"ols-t12-spec-text\">understand why entropy changes occur during:<div class=\"ols-t12-spec-sub-list\"><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">i<\/div><div class=\"ols-t12-spec-sub-text\">changes of state<\/div><\/div><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">ii<\/div><div class=\"ols-t12-spec-sub-text\">dissolving of a solid ionic lattice<\/div><\/div><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">iii<\/div><div class=\"ols-t12-spec-sub-text\">reactions in which there is a change in the number of moles from reactants to products<\/div><\/div><\/div><\/div><\/div>\n          <div class=\"ols-t12-spec-row ols-t12-spec-row--mid\"><div class=\"ols-t12-spec-code ols-t12-spec-code--mid\">12.6<\/div><div class=\"ols-t12-spec-text\"><div class=\"ols-t12-spec-sub-list\"><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">a<\/div><div class=\"ols-t12-spec-sub-text\">understand that total entropy change of any reaction is the sum of entropy change of system and entropy change of surroundings<\/div><\/div><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">b<\/div><div class=\"ols-t12-spec-sub-text\">know the expression \u0394Stotal = \u0394Ssystem + \u0394Ssurroundings<\/div><\/div><\/div><\/div><\/div>\n          <div class=\"ols-t12-spec-row ols-t12-spec-row--light\"><div class=\"ols-t12-spec-code\">12.7<\/div><div class=\"ols-t12-spec-text\">be able to calculate the entropy change of the system for a reaction, \u0394Ssystem, given the entropies of the reactants and products<\/div><\/div>\n          <div class=\"ols-t12-spec-row ols-t12-spec-row--mid\"><div class=\"ols-t12-spec-code ols-t12-spec-code--mid\">12.8<\/div><div class=\"ols-t12-spec-text\"><div class=\"ols-t12-spec-sub-list\"><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">a<\/div><div class=\"ols-t12-spec-sub-text\">be able to calculate entropy change in the surroundings using \u0394Ssurroundings = \u2212\u0394H\/T<\/div><\/div><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">b<\/div><div class=\"ols-t12-spec-sub-text\">be able to calculate \u0394Stotal using \u0394Ssurroundings = \u2212\u0394H\/T<\/div><\/div><\/div><\/div><\/div>\n          <div class=\"ols-t12-spec-row ols-t12-spec-row--light\"><div class=\"ols-t12-spec-code\">12.9<\/div><div class=\"ols-t12-spec-text\">understand that the feasibility of a reaction depends on:<div class=\"ols-t12-spec-sub-list\"><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">i<\/div><div class=\"ols-t12-spec-sub-text\">the balance between \u0394Ssystem and \u0394Ssurroundings, so that even endothermic reactions can occur spontaneously at room temperature<\/div><\/div><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">ii<\/div><div class=\"ols-t12-spec-sub-text\">temperature, as higher temperatures decrease the magnitude of \u0394Ssurroundings so its contribution to \u0394Stotal is less Students should be able to calculate the temperature at which a reaction is feasible. Students may also use \u0394G = \u0394H &#8211; T\u0394Ssystem in answers, although this approach is not a requirement of the specification.<\/div><\/div><\/div><\/div><\/div>\n          <div class=\"ols-t12-spec-row ols-t12-spec-row--mid\"><div class=\"ols-t12-spec-code ols-t12-spec-code--mid\">12.10<\/div><div class=\"ols-t12-spec-text\">understand that reactions can occur as long as \u0394Stotal is positive even if one of the other entropy changes is negative<\/div><\/div>\n          <div class=\"ols-t12-spec-row ols-t12-spec-row--light\"><div class=\"ols-t12-spec-code\">12.11<\/div><div class=\"ols-t12-spec-text\"><div class=\"ols-t12-spec-sub-list\"><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">a<\/div><div class=\"ols-t12-spec-sub-text\">understand thermodynamic stability<\/div><\/div><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">b<\/div><div class=\"ols-t12-spec-sub-text\">understand kinetic stability<\/div><\/div><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">c<\/div><div class=\"ols-t12-spec-sub-text\">distinguish between thermodynamic stability and kinetic stability<\/div><\/div><\/div><\/div><\/div>\n        <\/div>\n\n        <h3 class=\"ols-t12-spec-group-title\">12.12 &#8211; 12.19 Lattice energy, Born\u2013Haber cycles, solution and hydration<\/h3>\n        <div class=\"ols-t12-spec-rows\">\n          <div class=\"ols-t12-spec-row ols-t12-spec-row--mid\"><div class=\"ols-t12-spec-code ols-t12-spec-code--mid\">12.12<\/div><div class=\"ols-t12-spec-text\">be able to define the terms:<div class=\"ols-t12-spec-sub-list\"><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">i<\/div><div class=\"ols-t12-spec-sub-text\">standard enthalpy change of atomisation, \u0394atH<\/div><\/div><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">ii<\/div><div class=\"ols-t12-spec-sub-text\">electron affinity<\/div><\/div><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">iii<\/div><div class=\"ols-t12-spec-sub-text\">lattice energy (as the exothermic process for the formation of one mole of an ionic solid from its gaseous ions)<\/div><\/div><\/div><\/div><\/div>\n          <div class=\"ols-t12-spec-row ols-t12-spec-row--light\"><div class=\"ols-t12-spec-code\">12.13<\/div><div class=\"ols-t12-spec-text\"><div class=\"ols-t12-spec-sub-list\"><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">a<\/div><div class=\"ols-t12-spec-sub-text\">be able to construct Born-Haber cycles<\/div><\/div><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">b<\/div><div class=\"ols-t12-spec-sub-text\">be able to carry out calculations related to Born-Haber cycles<\/div><\/div><\/div><\/div><\/div>\n          <div class=\"ols-t12-spec-row ols-t12-spec-row--mid\"><div class=\"ols-t12-spec-code ols-t12-spec-code--mid\">12.14<\/div><div class=\"ols-t12-spec-text\">understand that a comparison of the experimental lattice energy value (from a Born-Haber cycle) with the theoretical value (obtained from electrostatic theory) in a particular compound indicates the degree of covalent bonding<\/div><\/div>\n          <div class=\"ols-t12-spec-row ols-t12-spec-row--light\"><div class=\"ols-t12-spec-code\">12.15<\/div><div class=\"ols-t12-spec-text\">understand that polarisation of anions by cations leads to some covalency in an ionic bond, based on evidence from the Born-Haber cycle<\/div><\/div>\n          <div class=\"ols-t12-spec-row ols-t12-spec-row--mid\"><div class=\"ols-t12-spec-code ols-t12-spec-code--mid\">12.16<\/div><div class=\"ols-t12-spec-text\"><div class=\"ols-t12-spec-sub-list\"><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">a<\/div><div class=\"ols-t12-spec-sub-text\">be able to define the term &#8216;enthalpy change of solution, \u0394solH&#8217;<\/div><\/div><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">b<\/div><div class=\"ols-t12-spec-sub-text\">be able to define the term &#8216;enthalpy change of hydration, \u0394hydH of an ion&#8217;<\/div><\/div><\/div><\/div><\/div>\n          <div class=\"ols-t12-spec-row ols-t12-spec-row--light\"><div class=\"ols-t12-spec-code\">12.17<\/div><div class=\"ols-t12-spec-text\"><div class=\"ols-t12-spec-sub-list\"><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">a<\/div><div class=\"ols-t12-spec-sub-text\">be able to use energy cycles to calculate enthalpy change of solution of an ionic compound using enthalpy change of hydration and lattice energy<\/div><\/div><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">b<\/div><div class=\"ols-t12-spec-sub-text\">be able to use energy level diagrams to calculate enthalpy change of solution of an ionic compound using enthalpy change of hydration and lattice energy<\/div><\/div><\/div><\/div><\/div>\n          <div class=\"ols-t12-spec-row ols-t12-spec-row--mid\"><div class=\"ols-t12-spec-code ols-t12-spec-code--mid\">12.18<\/div><div class=\"ols-t12-spec-text\"><div class=\"ols-t12-spec-sub-list\"><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">a<\/div><div class=\"ols-t12-spec-sub-text\">understand the effect of ionic charge on enthalpy change of hydration<\/div><\/div><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">b<\/div><div class=\"ols-t12-spec-sub-text\">understand the effect of ionic radius on enthalpy change of hydration<\/div><\/div><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">c<\/div><div class=\"ols-t12-spec-sub-text\">understand the effect of ionic charge on lattice energy<\/div><\/div><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">d<\/div><div class=\"ols-t12-spec-sub-text\">understand the effect of ionic radius on lattice energy<\/div><\/div><\/div><\/div><\/div>\n          <div class=\"ols-t12-spec-row ols-t12-spec-row--light\"><div class=\"ols-t12-spec-code\">12.19<\/div><div class=\"ols-t12-spec-text\"><div class=\"ols-t12-spec-sub-list\"><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">a<\/div><div class=\"ols-t12-spec-sub-text\">be able to use entropy changes of solution to predict solubility of ionic compounds<\/div><\/div><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">b<\/div><div class=\"ols-t12-spec-sub-text\">be able to use enthalpy changes of solution to predict solubility of ionic compounds<\/div><\/div><div class=\"ols-t12-spec-sub-row\"><div class=\"ols-t12-spec-sub-code\">c<\/div><div class=\"ols-t12-spec-sub-text\">be able to discuss trends in solubility of ionic compounds covered in Unit 2<\/div><\/div><\/div><\/div><\/div>\n        <\/div>\n      <\/div>\n    <\/div>\n  <\/section>\n\n<script type=\"application\/ld+json\">\n{\n  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