{"id":8348,"date":"2026-09-18T12:00:52","date_gmt":"2026-09-18T11:00:52","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-8-energetics-i\/"},"modified":"2026-09-18T12:08:24","modified_gmt":"2026-09-18T11:08:24","slug":"topic-8-energetics-i","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-8-energetics-i\/","title":{"rendered":"Topic 8 &#8211; Energetics I"},"content":{"rendered":"\n<div class=\"ols-t8-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 8 Energetics I<\/h4>\n\n    <ul class=\"ols-topic-list\">\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-8-energetics-i\/\">Topic 8 Overview<\/a>\n      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}\n\n      .ols-t8-topics {\n        padding: 52px 0 58px;\n      }\n\n      .ols-t8-cards-grid {\n        grid-template-columns: 1fr;\n        gap: 14px;\n      }\n\n      .ols-t8-spec-section {\n        padding: 52px 0 64px;\n      }\n\n      .ols-t8-spec-wrap {\n        padding: 24px 18px;\n        border-radius: 20px;\n      }\n\n      .ols-t8-info-grid {\n        grid-template-columns: 1fr 1fr;\n      }\n    }\n\n      .ols-t8-visual--exo { background: radial-gradient(circle at 24% 18%, rgba(255,255,255,0.46), transparent 24%), linear-gradient(135deg, #fff1f2 0%, #fb7185 45%, #be123c 100%); }\n    .ols-t8-visual--std { background: radial-gradient(circle at 24% 18%, rgba(255,255,255,0.46), transparent 24%), linear-gradient(135deg, #eef2ff 0%, #818cf8 45%, #3730a3 100%); }\n    .ols-t8-visual--calor { background: radial-gradient(circle at 24% 18%, rgba(255,255,255,0.46), transparent 24%), linear-gradient(135deg, #fffbeb 0%, #fbbf24 45%, #b45309 100%); }\n    .ols-t8-visual--hess { background: radial-gradient(circle at 24% 18%, rgba(255,255,255,0.46), transparent 24%), linear-gradient(135deg, #f0fdfa 0%, #2dd4bf 45%, #0f766e 100%); }\n    .ols-t8-visual--bond { background: radial-gradient(circle at 24% 18%, rgba(255,255,255,0.46), transparent 24%), linear-gradient(135deg, #f5f3ff 0%, #a78bfa 45%, #6d28d9 100%); }\n  <\/style>\n\n  <!-- BREADCRUMB BAR - sits above everything -->\n  <div class=\"ols-t8-breadcrumb-bar\">\n    <div class=\"ols-t8-container\">\n      <nav class=\"ols-t8-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\/\">Edexcel<\/a> \/\n          <span>Topic 8 Energetics I<\/span>\n        <\/nav>\n    <\/div>\n  <\/div>\n\n  <!-- INTRO -->\n  <section class=\"ols-t8-intro\">\n    <div class=\"ols-t8-container\">\n      <div class=\"ols-t8-intro-inner\">\n        <div>\n          <div class=\"ols-t8-eyebrow\">Edexcel A Level Chemistry<\/div>\n          <h1>Topic 8<br>Energetics I<\/h1>\n          <div class=\"ols-t8-accent-bar\"><\/div>\n          <p class=\"ols-t8-intro-lead\">Topic 8 introduces the heat energy changes that accompany chemical reactions. It covers exothermic and endothermic reactions, enthalpy level diagrams and reaction profiles, standard conditions and the standard enthalpy change definitions, measuring enthalpy changes by calorimetry, Hess&#8217;s law and enthalpy cycles, and mean bond enthalpies. The practical side is assessed in Core Practical 8.<\/p>\n        <\/div>\n        <div class=\"ols-t8-info-grid\">\n          <div class=\"ols-t8-info-card\"><div class=\"ols-t8-info-card-label\">Exam Paper<\/div><div class=\"ols-t8-info-card-value\">Paper 1<\/div><div class=\"ols-t8-info-card-sub\">9CH0\/01<\/div><\/div>\n          <div class=\"ols-t8-info-card\"><div class=\"ols-t8-info-card-label\">Specification Points<\/div><div class=\"ols-t8-info-card-value\">8.1 &#8211; 8.11<\/div><div class=\"ols-t8-info-card-sub\">11 points covered<\/div><\/div>\n          <div class=\"ols-t8-info-card\"><div class=\"ols-t8-info-card-label\">Topic Parts<\/div><div class=\"ols-t8-info-card-value\">5 pages<\/div><div class=\"ols-t8-info-card-sub\">Revision notes available<\/div><\/div>\n          <div class=\"ols-t8-info-card\"><div class=\"ols-t8-info-card-label\">Exam Board<\/div><div class=\"ols-t8-info-card-value\">Edexcel<\/div><div class=\"ols-t8-info-card-sub\">Pearson 9CH0<\/div><\/div>\n        <\/div>\n      <\/div>\n    <\/div>\n  <\/section>\n\n  <!-- TOPIC CARDS -->\n  <section class=\"ols-t8-topics\">\n    <div class=\"ols-t8-container\">\n\n      <div class=\"ols-t8-section-header\">\n        <h2 class=\"ols-t8-section-title\">Revision Notes<\/h2>\n      <\/div>\n\n      <div class=\"ols-t8-cards-grid\">\n\n        <!-- Card 1: Enthalpy Changes and Standard Conditions -->\n        <a class=\"ols-t8-card ols-t8-card--available\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-8-energetics-i\/enthalpy-changes-and-standard-conditions\/\">\n          <div class=\"ols-t8-card-img-wrap\">\n            <div class=\"ols-t8-visual ols-t8-visual--exo\">\n              <div class=\"ols-t8-visual-panel\">\n                <div class=\"ols-t8-visual-kicker\">Exo and endo<\/div>\n                <div class=\"ols-t8-visual-main\">Enthalpy<br>Changes<\/div>\n                <div class=\"ols-t8-visual-sub\">\u0394H, 298 K<\/div>\n              <\/div>\n            <\/div>\n            <div class=\"ols-t8-card-num\">1<\/div>\n            <span class=\"ols-t8-card-status ols-t8-card-status--available\">Available<\/span>\n          <\/div>\n          <div class=\"ols-t8-card-body\">\n            <p class=\"ols-t8-card-title\">Enthalpy Changes and Standard Conditions<\/p>\n            <p class=\"ols-t8-card-desc\">Exothermic and endothermic reactions, enthalpy level diagrams, activation energy and standard conditions.<\/p>\n            <span class=\"ols-t8-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: Standard Enthalpy Changes -->\n        <a class=\"ols-t8-card ols-t8-card--available\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-8-energetics-i\/standard-enthalpy-changes\/\">\n          <div class=\"ols-t8-card-img-wrap\">\n            <div class=\"ols-t8-visual ols-t8-visual--std\">\n              <div class=\"ols-t8-visual-panel\">\n                <div class=\"ols-t8-visual-kicker\">Definitions<\/div>\n                <div class=\"ols-t8-visual-main\">Standard<br>Enthalpies<\/div>\n                <div class=\"ols-t8-visual-sub\">\u0394fH, \u0394cH, \u0394neutH<\/div>\n              <\/div>\n            <\/div>\n            <div class=\"ols-t8-card-num\">2<\/div>\n            <span class=\"ols-t8-card-status ols-t8-card-status--available\">Available<\/span>\n          <\/div>\n          <div class=\"ols-t8-card-body\">\n            <p class=\"ols-t8-card-title\">Standard Enthalpy Changes<\/p>\n            <p class=\"ols-t8-card-desc\">The standard enthalpy change definitions and the equation each one refers to.<\/p>\n            <span class=\"ols-t8-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: Calorimetry: Measuring Enthalpy Changes -->\n        <a class=\"ols-t8-card ols-t8-card--available\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-8-energetics-i\/calorimetry-measuring-enthalpy-changes\/\">\n          <div class=\"ols-t8-card-img-wrap\">\n            <div class=\"ols-t8-visual ols-t8-visual--calor\">\n              <div class=\"ols-t8-visual-panel\">\n                <div class=\"ols-t8-visual-kicker\">q = mc\u0394T<\/div>\n                <div class=\"ols-t8-visual-main\">Calorimetry<\/div>\n                <div class=\"ols-t8-visual-sub\">q = mc\u0394T<\/div>\n              <\/div>\n            <\/div>\n            <div class=\"ols-t8-card-num\">3<\/div>\n            <span class=\"ols-t8-card-status ols-t8-card-status--available\">Available<\/span>\n          <\/div>\n          <div class=\"ols-t8-card-body\">\n            <p class=\"ols-t8-card-title\">Calorimetry: Measuring Enthalpy Changes<\/p>\n            <p class=\"ols-t8-card-desc\">Calculating \u0394H from a temperature change, cooling curve corrections, errors and assumptions.<\/p>\n            <span class=\"ols-t8-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: Hess's Law and Enthalpy Cycles -->\n        <a class=\"ols-t8-card ols-t8-card--available\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-8-energetics-i\/hess-law-and-enthalpy-cycles\/\">\n          <div class=\"ols-t8-card-img-wrap\">\n            <div class=\"ols-t8-visual ols-t8-visual--hess\">\n              <div class=\"ols-t8-visual-panel\">\n                <div class=\"ols-t8-visual-kicker\">Enthalpy cycles<\/div>\n                <div class=\"ols-t8-visual-main\">Hess&#8217;s<br>Law<\/div>\n                <div class=\"ols-t8-visual-sub\">route A = route B<\/div>\n              <\/div>\n            <\/div>\n            <div class=\"ols-t8-card-num\">4<\/div>\n            <span class=\"ols-t8-card-status ols-t8-card-status--available\">Available<\/span>\n          <\/div>\n          <div class=\"ols-t8-card-body\">\n            <p class=\"ols-t8-card-title\">Hess&#8217;s Law and Enthalpy Cycles<\/p>\n            <p class=\"ols-t8-card-desc\">Building enthalpy cycles and calculating \u0394H from formation and combustion data.<\/p>\n            <span class=\"ols-t8-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: Bond Enthalpies -->\n        <a class=\"ols-t8-card ols-t8-card--available\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-8-energetics-i\/bond-enthalpies\/\">\n          <div class=\"ols-t8-card-img-wrap\">\n            <div class=\"ols-t8-visual ols-t8-visual--bond\">\n              <div class=\"ols-t8-visual-panel\">\n                <div class=\"ols-t8-visual-kicker\">Break and make<\/div>\n                <div class=\"ols-t8-visual-main\">Bond<br>Enthalpies<\/div>\n                <div class=\"ols-t8-visual-sub\">broken \u2212 made<\/div>\n              <\/div>\n            <\/div>\n            <div class=\"ols-t8-card-num\">5<\/div>\n            <span class=\"ols-t8-card-status ols-t8-card-status--available\">Available<\/span>\n          <\/div>\n          <div class=\"ols-t8-card-body\">\n            <p class=\"ols-t8-card-title\">Bond Enthalpies<\/p>\n            <p class=\"ols-t8-card-desc\">Mean bond enthalpy, calculating \u0394H from bonds broken and made, and why the answers differ from Hess values.<\/p>\n            <span class=\"ols-t8-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-t8-spec-section\">\n    <div class=\"ols-t8-container\">\n      <div class=\"ols-t8-spec-wrap\">\n        <div class=\"ols-t8-spec-pill\">Specification Coverage<\/div>\n        <h2 class=\"ols-t8-spec-heading\">Topic 8 Energetics I &#8211; Edexcel A Level Chemistry<\/h2>\n        <p class=\"ols-t8-spec-intro-text\">The following specification points outline the knowledge and skills students are expected to demonstrate for Topic 8. Energetics I is extended in Topic 13 Energetics II.<\/p>\n        <h3 class=\"ols-t8-spec-group-title\">Enthalpy Changes and Standard Conditions<\/h3>\n        <div class=\"ols-t8-spec-rows\">\n          <div class=\"ols-t8-spec-row ols-t8-spec-row--light\"><div class=\"ols-t8-spec-code\">8.1<\/div><div class=\"ols-t8-spec-text\">know that standard conditions are 100 kPa and a specified temperature, usually 298 K<\/div><\/div>\n          <div class=\"ols-t8-spec-row ols-t8-spec-row--mid\"><div class=\"ols-t8-spec-code ols-t8-spec-code--mid\">8.2<\/div><div class=\"ols-t8-spec-text\">know that the enthalpy change is the heat energy change measured at constant pressure<\/div><\/div>\n          <div class=\"ols-t8-spec-row ols-t8-spec-row--light\"><div class=\"ols-t8-spec-code\">8.3<\/div><div class=\"ols-t8-spec-text\">be able to construct and interpret enthalpy level diagrams showing an enthalpy change, including appropriate signs for exothermic and endothermic reactions; activation energy is shown in reaction profile diagrams but not in enthalpy level diagrams<\/div><\/div>\n        <\/div>\n\n        <h3 class=\"ols-t8-spec-group-title\">Standard Enthalpy Changes<\/h3>\n        <div class=\"ols-t8-spec-rows\">\n          <div class=\"ols-t8-spec-row ols-t8-spec-row--mid\"><div class=\"ols-t8-spec-code ols-t8-spec-code--mid\">8.4<\/div><div class=\"ols-t8-spec-text\">be able to define standard enthalpy change of:<div class=\"ols-t8-spec-sub-list\"><div class=\"ols-t8-spec-sub-row\"><div class=\"ols-t8-spec-sub-code\">i<\/div><div class=\"ols-t8-spec-sub-text\">reaction<\/div><\/div><div class=\"ols-t8-spec-sub-row\"><div class=\"ols-t8-spec-sub-code\">ii<\/div><div class=\"ols-t8-spec-sub-text\">formation<\/div><\/div><div class=\"ols-t8-spec-sub-row\"><div class=\"ols-t8-spec-sub-code\">iii<\/div><div class=\"ols-t8-spec-sub-text\">combustion<\/div><\/div><div class=\"ols-t8-spec-sub-row\"><div class=\"ols-t8-spec-sub-code\">iv<\/div><div class=\"ols-t8-spec-sub-text\">neutralisation<\/div><\/div><\/div><\/div><\/div>\n        <\/div>\n\n        <h3 class=\"ols-t8-spec-group-title\">Measuring Enthalpy Changes<\/h3>\n        <div class=\"ols-t8-spec-rows\">\n          <div class=\"ols-t8-spec-row ols-t8-spec-row--light\"><div class=\"ols-t8-spec-code\">8.5<\/div><div class=\"ols-t8-spec-text\">understand experiments to measure enthalpy changes in terms of:<div class=\"ols-t8-spec-sub-list\"><div class=\"ols-t8-spec-sub-row\"><div class=\"ols-t8-spec-sub-code\">i<\/div><div class=\"ols-t8-spec-sub-text\">processing results using the expression: energy transferred = mass \u00d7 specific heat capacity \u00d7 temperature change (Q = mc\u0394T)<\/div><\/div><div class=\"ols-t8-spec-sub-row\"><div class=\"ols-t8-spec-sub-code\">ii<\/div><div class=\"ols-t8-spec-sub-text\">evaluating sources of error and assumptions made in the experiments<\/div><\/div><\/div><\/div><\/div>\n          <div class=\"ols-t8-spec-row ols-t8-spec-row--mid\"><div class=\"ols-t8-spec-code ols-t8-spec-code--mid\">8.6<\/div><div class=\"ols-t8-spec-text\">be able to calculate enthalpy changes in kJ mol\u207b\u00b9 from given experimental results; both a sign and units are expected in the final answer<\/div><\/div>\n        <\/div>\n\n        <h3 class=\"ols-t8-spec-group-title\">Hess&#8217;s Law<\/h3>\n        <div class=\"ols-t8-spec-rows\">\n          <div class=\"ols-t8-spec-row ols-t8-spec-row--light\"><div class=\"ols-t8-spec-code\">8.7<\/div><div class=\"ols-t8-spec-text\">be able to construct enthalpy cycles using Hess&#8217;s Law<\/div><\/div>\n          <div class=\"ols-t8-spec-row ols-t8-spec-row--mid\"><div class=\"ols-t8-spec-code ols-t8-spec-code--mid\">8.8<\/div><div class=\"ols-t8-spec-text\">be able to calculate enthalpy changes from data using Hess&#8217;s Law<\/div><\/div>\n        <\/div>\n\n        <h3 class=\"ols-t8-spec-group-title\">Bond Enthalpies<\/h3>\n        <div class=\"ols-t8-spec-rows\">\n          <div class=\"ols-t8-spec-row ols-t8-spec-row--light\"><div class=\"ols-t8-spec-code\">8.9<\/div><div class=\"ols-t8-spec-text\">know what is meant by the terms &#8216;bond enthalpy&#8217; and &#8216;mean bond enthalpy&#8217;<\/div><\/div>\n          <div class=\"ols-t8-spec-row ols-t8-spec-row--mid\"><div class=\"ols-t8-spec-code ols-t8-spec-code--mid\">8.10<\/div><div class=\"ols-t8-spec-text\">be able to calculate an enthalpy change of reaction using mean bond enthalpies and explain the limitations of this method of calculation<\/div><\/div>\n          <div class=\"ols-t8-spec-row ols-t8-spec-row--light\"><div class=\"ols-t8-spec-code\">8.11<\/div><div class=\"ols-t8-spec-text\">be able to calculate mean bond enthalpies from enthalpy changes of reaction<\/div><\/div>\n        <\/div>\n      <\/div>\n    <\/div>\n  <\/section>\n\n<script type=\"application\/ld+json\">\n{\n  \"@context\": \"https:\/\/schema.org\",\n  \"@graph\": [\n    {\n      \"@type\": \"CollectionPage\",\n 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