{"id":3506,"date":"2026-05-14T06:22:14","date_gmt":"2026-05-14T05:22:14","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/?page_id=3506"},"modified":"2026-06-28T05:54:42","modified_gmt":"2026-06-28T04:54:42","slug":"hazard-and-risk","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/hazard-and-risk\/","title":{"rendered":"Hazard &#038; Risk"},"content":{"rendered":"\n<section class=\"ols-revision-page ols-hazard-risk-page\">\n  <style>\n    .ols-revision-page {\n      --navy: #1C244B;\n      --blue: #2563eb;\n      --soft-blue: #eef4ff;\n      --soft-red: #fff7f7;\n      --soft-purple: #f7f0ff;\n      --soft-green: #f0f7f1;\n      --soft-yellow: #fff8e6;\n      --red: #c81e1e;\n      --gold: #c9973a;\n      --green: #3f8f46;\n      --grey-text: #667085;\n      --body-text: #1f2937;\n      --border: rgba(28, 36, 75, 0.14);\n      --shadow: 0 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var(--grey-text);\n    }\n\n    .ols-linkedin-pill {\n      display: inline-flex;\n      align-items: center;\n      justify-content: center;\n      gap: 10px;\n      margin-top: 16px;\n      padding: 11px 18px;\n      border-radius: 999px;\n      background: linear-gradient(135deg, #0A66C2, #004182);\n      color: #ffffff;\n      text-decoration: none;\n      font-size: 14px;\n      line-height: 1;\n      font-weight: 700;\n      letter-spacing: 0.01em;\n      box-shadow: 0 10px 22px rgba(10, 102, 194, 0.24);\n      position: relative;\n      overflow: hidden;\n      transition: transform 0.22s ease, box-shadow 0.22s ease;\n    }\n\n    .ols-linkedin-pill:hover {\n      transform: translateY(-3px) scale(1.03);\n      box-shadow: 0 16px 34px rgba(10, 102, 194, 0.34), 0 0 0 6px rgba(10, 102, 194, 0.10);\n    }\n\n    .ols-linkedin-icon {\n      width: 18px;\n      height: 18px;\n      display: block;\n      flex-shrink: 0;\n    }\n\n    .ols-attribution-card {\n      background: linear-gradient(135deg, #ffffff, #f8fbff);\n      border: 1px solid rgba(28, 36, 75, 0.14);\n      border-radius: 28px;\n      box-shadow: 0 18px 45px rgba(28, 36, 75, 0.10);\n      padding: 34px;\n      margin-bottom: 24px;\n      overflow: hidden;\n      box-sizing: border-box;\n    }\n\n    .ols-attribution-card p {\n      margin: 0;\n      font-size: 14px;\n      line-height: 1.65;\n      font-weight: 300;\n      color: #667085;\n    }\n\n    .ols-attribution-card strong {\n      font-weight: 700;\n      color: #1C244B;\n    }\n\n  <\/style>\n\n  <aside class=\"ols-sidebar\">\r\n  <div class=\"ols-sidebar-header\">\r\n    <h3>Revision Notes<\/h3>\r\n    <p>A Level Chemistry<\/p>\r\n  <\/div>\r\n\r\n  <div class=\"ols-topic-group\">\r\n    <h4>Topic 4 Organic Chemistry &amp; Alkanes<\/h4>\r\n\r\n    <ul class=\"ols-topic-list\">\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/hazard-and-risk\/\">Hazard &amp; Risk<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/organic-chemistry\/\">Introduction To Organic Chemistry<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/organic-chemistry\/iupac-rules\/\">IUPAC Rules<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/organic-chemistry\/alkene\/\">Alkene<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/organic-chemistry\/alcohol\/\">Alcohol<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/organic-chemistry\/halogenoalkanes\/\">Halogenoalkanes<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/organic-chemistry\/aldehyde\/\">Aldehyde<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/organic-chemistry\/ketone\/\">Ketone<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/organic-chemistry\/carboxylic-acid\/\">Carboxylic Acid<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/organic-chemistry\/ester\/\">Ester<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/isomerism\/\">Isomerism<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/crude-oil\/\">Alkanes from Crude Oil<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/crude-oil\/fractional-distillation\/\">Fractional Distillation<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/crude-oil\/cracking\/\">Cracking<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/crude-oil\/reforming\/\">Reforming<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/fuel\/\">Alkanes as Fuel<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/fuel\/combustion\/\">Combustion<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/fuel\/oxides-of-sulfur\/\">Oxides of Sulfur<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/fuel\/oxides-of-nitrogen\/\">Oxides of Nitrogen<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/fuel\/catalytic-converter\/\">Catalytic Converter<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/alternative-fuel\/\">Alternative Fuel<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/reactions\/\">Reactions of Alkanes<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/reactions\/free-radical-substitution\/\">Free Radical Substitution<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/reactions\/initiation\/\">Initiation<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/reactions\/propagation\/\">Propagation<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/reactions\/termination\/\">Termination<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/reactions\/further-substitution\/\">Further Substitution<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n    <\/ul>\r\n  <\/div>\r\n\r\n  <div class=\"ols-topic-group\">\r\n    <h4>Next Topics<\/h4>\r\n\r\n    <ul class=\"ols-topic-list\">\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-5-alkenes\/\">Alkenes<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-6-energetics\/\">Energetics<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-7-intermolecular-forces\/\">Intermolecular Forces<\/a>\r\n      <\/li>\r\n    <\/ul>\r\n  <\/div>\r\n<\/aside>\r\n\r\n<script>\r\n(function() {\r\n  function normalisePath(path) {\r\n    return String(path || '')\r\n      .split('?')[0]\r\n      .split('#')[0]\r\n      .replace(\/\\\/+$\/, '')\r\n      .toLowerCase();\r\n  }\r\n\r\n  function highlightActive() {\r\n    var sidebar = document.querySelector('.ols-sidebar');\r\n    if (!sidebar) return false;\r\n\r\n    var currentPath = normalisePath(window.location.pathname);\r\n    var links = sidebar.querySelectorAll('a[href]');\r\n    var matched = null;\r\n    var matchedLength = 0;\r\n\r\n    sidebar.querySelectorAll('.active, 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href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/\">Topic 4 Organic Chemistry &amp; Alkanes<\/a> \/\n        <span>Hazard &amp; Risk<\/span>\n      <\/nav>\n\n      <header class=\"ols-title-card\">\n        <h1>Hazard &amp; Risk<\/h1>\n        <p class=\"ols-page-intro\">A concise revision guide to the difference between hazards and risks in practical chemistry, including common laboratory hazards and how risk can be reduced during experiments.<\/p>\n\n        <div class=\"ols-badges\">\n          <div class=\"ols-badge\">Exam board: Edexcel International<\/div>\n          <div class=\"ols-badge\">Topic 4: Organic Chemistry &amp; Alkanes<\/div>\n          <div class=\"ols-badge\">Level: A Level Chemistry<\/div>\n        <\/div>\n\n        <div class=\"ols-author\">\n          <img decoding=\"async\"\n            class=\"ols-author-avatar-img\"\n            src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Author-Profile.jpeg\"\n            alt=\"Dr. Mohammed Al-Fatah\"\n          >\n\n          <div class=\"ols-author-content\">\n            <h2 class=\"ols-author-title\">Written by: Dr. Mohammed Al-Fatah<\/h2>\n            <p class=\"ols-author-description\">Chemistry specialist revision notes for A Level Chemistry.<\/p>\n\n            <a class=\"ols-linkedin-pill\" href=\"https:\/\/www.linkedin.com\/in\/doctormohammedfatah\/\" target=\"_blank\" rel=\"noopener noreferrer\">\n              <svg class=\"ols-linkedin-icon\" viewBox=\"0 0 24 24\" fill=\"currentColor\" aria-hidden=\"true\">\n                <path d=\"M4.98 3.5C4.98 4.88 3.86 6 2.48 6S0 4.88 0 3.5 1.12 1 2.48 1s2.5 1.12 2.5 2.5zM.5 8h4V24h-4V8zm7 0h3.8v2.2h.1c.5-.9 1.8-2.2 3.9-2.2 4.2 0 5 2.8 5 6.4V24h-4v-7.6c0-1.8 0-4.2-2.6-4.2s-3 2-3 4v7.8h-4V8z\"\/>\n              <\/svg>\n              View LinkedIn Profile\n            <\/a>\n          <\/div>\n        <\/div>\n      <\/header>\n\n      <article class=\"ols-note-card soft\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">1<\/div>\n          <h2>What Is a Hazard?<\/h2>\n        <\/div>\n\n        <p>A <strong>hazard<\/strong> is a substance or procedure that has the <strong>potential to cause harm<\/strong>.<\/p>\n        <p>In chemistry, a hazard might be linked to a chemical substance, a piece of apparatus, a flame, a sharp object, a hot surface, pressure build-up or a practical procedure.<\/p>\n\n        <div class=\"ols-definition-box\">\n          <div class=\"ols-definition-circle\">Hazard<\/div>\n          <p><strong>Definition:<\/strong> A hazard is something that could cause harm. It describes the possible danger before considering how likely that harm is to happen.<\/p>\n        <\/div>\n\n        <div class=\"ols-figure-card\">\n          <div class=\"ols-figure-image\">\n            <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/hazard.webp\" alt=\"Laboratory hazard scene with warning signs, chemical containers and flammable materials.\">\n          <\/div>\n          <div class=\"ols-figure-caption\">\n            <p>Hazards may come from the chemical itself, such as toxicity or flammability, or from how the substance or equipment is used.<\/p>\n          <\/div>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">2<\/div>\n          <h2>Common Laboratory Hazards<\/h2>\n        <\/div>\n\n        <p>Laboratory chemicals are often labelled according to the type of hazard they present. These labels help students and teachers decide what precautions are needed before practical work begins.<\/p>\n\n        <div class=\"ols-hazard-grid\">\n          <div class=\"ols-hazard-pill\"><strong>Toxic<\/strong><span>Can cause serious harm if swallowed, inhaled or absorbed through the skin.<\/span><\/div>\n          <div class=\"ols-hazard-pill\"><strong>Flammable<\/strong><span>Can catch fire easily, especially near naked flames or sparks.<\/span><\/div>\n          <div class=\"ols-hazard-pill\"><strong>Harmful<\/strong><span>Can cause damage to health, but is usually less severe than toxic substances.<\/span><\/div>\n          <div class=\"ols-hazard-pill\"><strong>Irritant<\/strong><span>Can cause redness, itching or inflammation, especially on skin or in eyes.<\/span><\/div>\n          <div class=\"ols-hazard-pill\"><strong>Corrosive<\/strong><span>Can attack and destroy living tissue or damage materials.<\/span><\/div>\n          <div class=\"ols-hazard-pill\"><strong>Oxidising<\/strong><span>Can make other substances burn more easily by supplying oxygen or supporting oxidation.<\/span><\/div>\n          <div class=\"ols-hazard-pill\"><strong>Carcinogenic<\/strong><span>May increase the risk of cancer after exposure.<\/span><\/div>\n        <\/div>\n\n        <div class=\"ols-warning-box\">\n          <p><strong>Important:<\/strong> The hazard describes the potential for harm. It does not automatically tell you how likely harm is under the exact practical conditions used.<\/p>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card purple\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">3<\/div>\n          <h2>What Is Risk?<\/h2>\n        <\/div>\n\n        <p><strong>Risk<\/strong> is the <strong>likelihood or chance<\/strong> that harm will occur as a result of using a hazardous substance or carrying out a procedure.<\/p>\n        <p>This means a hazardous substance can sometimes pose a lower risk if it is used in a <strong>low concentration<\/strong>, in a <strong>small amount<\/strong>, or with suitable safety precautions.<\/p>\n\n        <div class=\"ols-definition-box\">\n          <div class=\"ols-definition-circle\">Risk<\/div>\n          <p><strong>Definition:<\/strong> Risk describes how likely harm is to occur in a specific situation. It depends on the hazard, the quantity, the concentration, the method and the precautions used.<\/p>\n        <\/div>\n\n        <div class=\"ols-figure-card\">\n          <div class=\"ols-figure-image\">\n            <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/risk.webp\" alt=\"Laboratory risk reduction scene with safety goggles, gloves, checklists and chemical equipment.\">\n          <\/div>\n          <div class=\"ols-figure-caption\">\n            <p>Risk is reduced by controlling how hazardous substances are handled, stored and used during practical work.<\/p>\n          <\/div>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card green\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">4<\/div>\n          <h2>Hazard Compared with Risk<\/h2>\n        <\/div>\n\n        <p>Students often confuse hazard and risk. A hazard is the possible source of harm. Risk is the chance that the harm will actually happen under the conditions used.<\/p>\n\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Term<\/th>\n                <th>Meaning<\/th>\n                <th>Example in the laboratory<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td data-label=\"Term\"><strong>Hazard<\/strong><\/td>\n                <td data-label=\"Meaning\">A substance or procedure with the potential to cause harm.<\/td>\n                <td data-label=\"Example in the laboratory\">Concentrated acid is corrosive because it can damage living tissue.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Term\"><strong>Risk<\/strong><\/td>\n                <td data-label=\"Meaning\">The likelihood that harm will occur in a particular situation.<\/td>\n                <td data-label=\"Example in the laboratory\">The risk is lower if dilute acid is used in small amounts while wearing eye protection.<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Exam focus:<\/strong> If a question asks how to reduce risk, give a practical control measure, not just the name of the hazard.<\/p>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card yellow\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">5<\/div>\n          <h2>How Risks Can Be Reduced<\/h2>\n        <\/div>\n\n        <p>Risks can be reduced by changing the scale of the experiment, changing the method or using precautions specific to the hazard.<\/p>\n\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Method of reducing risk<\/th>\n                <th>What this means<\/th>\n                <th>Why it works<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td data-label=\"Method of reducing risk\"><strong>Work on a smaller scale<\/strong><\/td>\n                <td data-label=\"What this means\">Use smaller amounts of the hazardous substance.<\/td>\n                <td data-label=\"Why it works\">Less material is available to spill, burn, react or release harmful vapour.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Method of reducing risk\"><strong>Use specific precautions<\/strong><\/td>\n                <td data-label=\"What this means\">Choose safety measures that match the hazard.<\/td>\n                <td data-label=\"Why it works\">The control measure directly reduces the chance of harm from that particular hazard.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Method of reducing risk\"><strong>Use an alternative method<\/strong><\/td>\n                <td data-label=\"What this means\">Use a safer procedure or less hazardous substance where possible.<\/td>\n                <td data-label=\"Why it works\">Replacing the hazard, or reducing its severity, reduces the overall risk.<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Hazard type<\/th>\n                <th>Suitable precaution<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td data-label=\"Hazard type\"><strong>Irritant substances<\/strong><\/td>\n                <td data-label=\"Suitable precaution\">Wear safety goggles, especially when using dilute acids and alkalis.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Hazard type\"><strong>Corrosive substances<\/strong><\/td>\n                <td data-label=\"Suitable precaution\">Wear goggles when handling strong acids and alkalis.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Hazard type\"><strong>Flammable substances<\/strong><\/td>\n                <td data-label=\"Suitable precaution\">Keep away from naked flames.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Hazard type\"><strong>Toxic substances<\/strong><\/td>\n                <td data-label=\"Suitable precaution\">Wear gloves, avoid skin contact and wash hands after use.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Hazard type\"><strong>Oxidising substances<\/strong><\/td>\n                <td data-label=\"Suitable precaution\">Keep away from flammable or easily oxidised materials.<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card soft\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">6<\/div>\n          <h2>Common Exam Mistakes<\/h2>\n        <\/div>\n\n        <ul>\n          <li>Do not define hazard as the chance of harm. That is <strong>risk<\/strong>.<\/li>\n          <li>Do not define risk as simply \u201cdanger\u201d. Risk is the <strong>likelihood<\/strong> that harm will occur.<\/li>\n          <li>Do not give vague precautions such as \u201cbe careful\u201d. Give a specific safety measure linked to the hazard.<\/li>\n          <li>Do not assume a hazardous chemical always has high risk. Concentration, amount and precautions affect risk.<\/li>\n        <\/ul>\n      <\/article>\n\n      <section class=\"ols-h5p-card\">\n        <h2>Check Your Understanding<\/h2>\n        <p>Use these short activities to check the difference between hazard, risk and risk reduction before moving on.<\/p>\n\n        <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-60\" class=\"h5p-iframe\" data-content-id=\"60\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"T4.1.1 Drag: Hazard and Risk Key Concepts\"><\/iframe><\/div><\/div>\n        <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-61\" class=\"h5p-iframe\" data-content-id=\"61\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"T4.1.2 MCQ: Hazard Definition\"><\/iframe><\/div><\/div>\n        <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-62\" class=\"h5p-iframe\" data-content-id=\"62\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"T4.1.3 MCQ: Reducing Risk\"><\/iframe><\/div><\/div>\n        <div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-63\" class=\"h5p-iframe\" data-content-id=\"63\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"T4.1.4 MCQ: Flammable Substance Precautions\"><\/iframe><\/div><\/div>\n      <\/section>\n\n      <section class=\"ols-course-cta-alkenes\" id=\"olsCourseCtaAlkenes001\">\n        <style>\n          .ols-course-cta-alkenes,\n          .ols-course-cta-alkenes * {\n            box-sizing: border-box;\n          }\n\n          .ols-course-cta-alkenes {\n            --navy: #1C244B;\n            --blue: #2563eb;\n            --body-text: #1f2937;\n            --grey-text: #667085;\n            --border: rgba(28, 36, 75, 0.14);\n            --shadow: 0 18px 45px rgba(28, 36, 75, 0.12);\n 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and Alkanes course page\">\n\n              <div class=\"ols-course-cta-image\">\n                <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/04\/edexcel-international-a-level-chemistry-topic-4a-4b-organic-chemistry-alkanes-course-banner.jpg\" alt=\"Edexcel International A Level Chemistry Topic 4A\/B Organic Chemistry and Alkanes course banner\">\n              <\/div>\n\n            <\/a>\n\n            <div class=\"ols-course-cta-content\">\n\n              <div class=\"ols-course-cta-header-row\">\n\n                <div class=\"ols-course-cta-kicker\">\n                  Complete Topic 4A\/B Organic Chemistry &amp; Alkanes Course\n                <\/div>\n\n                <a class=\"ols-course-button ols-course-button-top\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/product\/organic-chemistry-alkanes-topic-4ab-edexcel-international\/\">\n                  View Course\n                <\/a>\n\n              <\/div>\n\n              <h2>\n                Master Organic Chemistry and Alkanes for Edexcel International A Level Chemistry\n              <\/h2>\n\n            <\/div>\n\n          <\/div>\n\n          <div class=\"ols-course-cta-intro-stats\">\n\n            <p class=\"ols-course-cta-intro\">\n              Continue from these free revision notes into the full Topic 4A\/B Organic Chemistry and Alkanes course, with guided video teaching, diagnostic MCQ practice, teacher-marked short-answer questions and a specification assignment with a personalised progress report.\n            <\/p>\n\n            <div class=\"ols-course-cta-stats\">\n\n              <div class=\"ols-course-stat\">\n                <span>Guided learning<\/span>\n                <strong>16 hours<\/strong>\n              <\/div>\n\n              <div class=\"ols-course-stat\">\n                <span>Video lessons<\/span>\n                <strong>430 mins<\/strong>\n              <\/div>\n\n              <div class=\"ols-course-stat\">\n                <span>MCQ practice<\/span>\n                <strong>73 marks<\/strong>\n              <\/div>\n\n              <div class=\"ols-course-stat\">\n                <span>SAQ practice<\/span>\n                <strong>30 marks<\/strong>\n              <\/div>\n\n            <\/div>\n\n          <\/div>\n\n          <div class=\"ols-course-cta-features\">\n\n            <div class=\"ols-course-feature\">\n              <h3>Guided video teaching<\/h3>\n              <p>\n                Learn the chemistry and exam technique through structured video lessons with worked examples and walkthroughs.\n              <\/p>\n            <\/div>\n\n            <div class=\"ols-course-feature\">\n              <h3>Instant MCQ feedback<\/h3>\n              <p>\n                Auto-marked MCQ quizzes provide immediate diagnostic feedback for every answer choice.\n              <\/p>\n            <\/div>\n\n            <div class=\"ols-course-feature\">\n        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<tr><td>Cl<sup>\u2212<\/sup><\/td><td>0.180<\/td><\/tr>\n                    <\/tbody>\n                  <\/table>\n\n                  <p class=\"mcq-question-main\">Which compound has the strongest ionic bonding?<\/p>\n\n                  <div class=\"mcq-options-wrap\">\n                    <div id=\"mcqWrongOption\" class=\"mcq-option-row\">\n                      <span class=\"mcq-radio\"><\/span>\n                      <span class=\"mcq-radio-ripple\"><\/span>\n                      <span class=\"mcq-option-label\">sodium chloride<\/span>\n\n                      <span id=\"mcqSpecificFeedback\" class=\"mcq-specific-feedback\">\n                        <span id=\"mcqCrossIcon\" class=\"mcq-cross-icon\">\u00d7<\/span>\n                        <span class=\"mcq-specific-feedback-text\">\n                          <span id=\"mcqSpecificText\"><\/span><span id=\"mcqSpecificCursor\" class=\"cursor mcq-specific-cursor\" style=\"display:none;\"><\/span>\n                        <\/span>\n                      <\/span>\n                    <\/div>\n\n                    <div class=\"mcq-option-row\"><span class=\"mcq-radio\"><\/span><span class=\"mcq-radio-ripple\"><\/span><span class=\"mcq-option-label\">potassium chloride<\/span><\/div>\n                    <div class=\"mcq-option-row\"><span class=\"mcq-radio\"><\/span><span class=\"mcq-radio-ripple\"><\/span><span class=\"mcq-option-label\">sodium fluoride<\/span><\/div>\n                    <div class=\"mcq-option-row\"><span class=\"mcq-radio\"><\/span><span class=\"mcq-radio-ripple\"><\/span><span class=\"mcq-option-label\">potassium fluoride<\/span><\/div>\n                  <\/div>\n\n                  <button id=\"mcqSubmitButton\" class=\"mcq-submit-button\">Submit answer<\/button>\n                <\/section>\n\n                <section id=\"mcqGeneralFeedback\" class=\"mcq-general-feedback\">\n                  <span id=\"mcqGeneralText\"><\/span><span id=\"mcqGeneralCursor\" class=\"cursor 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is incorrect.\\n\\n\"+\n      \"To determine which compound has the strongest ionic bonding, recall the key principle:\\n\\n\"+\n      \"\u2022 Ionic bond strength increases when ionic radii are small, because the ions can get closer together.\\n\"+\n      \"\u2022 Smaller ions \u2192 stronger electrostatic attraction \u2192 stronger ionic lattice.\\n\"+\n      \"\u2022 Na\u207a (0.102 nm) is smaller than K\u207a (0.138 nm).\\n\"+\n      \"\u2022 F\u207b (0.133 nm) is smaller than Cl\u207b (0.180 nm).\\n\\n\"+\n      \"Therefore, the strongest ionic bonding occurs in the compound formed by the smallest cation and the smallest anion \u2192 sodium fluoride (NaF).\\n\\n\"+\n      \"The correct answer is: sodium fluoride\";\n\n      const mcqIntroScreen=document.getElementById(\"mcqIntroScreen\");\n      const mcqIntroTitleText=document.getElementById(\"mcqIntroTitleText\");\n      const mcqIntroTitleCursor=document.getElementById(\"mcqIntroTitleCursor\");\n      const 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Melting temperature is a result of bonding strength, not the cause of it.\\n\\n\"+\n      \"In metallic bonding, positive metal ions are attracted to a sea of delocalised electrons. The strength of this attraction depends on the charge of the ions and the number of delocalised electrons.\\n\\n\"+\n      \"Magnesium forms Mg\u00b2\u207a ions and contributes two delocalised electrons per atom, whereas sodium forms Na\u207a ions and contributes only one electron. This results in a stronger electrostatic attraction in magnesium. Additionally, Mg\u00b2\u207a ions have a higher charge density than Na\u207a ions, further strengthening the metallic bonding.\\n\\n\"+\n      \"Next time, include:\\n\"+\n      \"\u2022 Ion charge: magnesium forms Mg\u00b2\u207a, sodium forms Na\u207a \u2713\\n\"+\n      \"\u2022 Delocalised electrons: magnesium provides more electrons to the sea \u2713\\n\"+\n      \"\u2022 Charge density: smaller, more highly charged ions create stronger attraction \u2713\\n\\n\"+\n      \"You were close. 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