{"id":37979,"date":"2026-04-08T17:08:04","date_gmt":"2026-04-08T10:08:04","guid":{"rendered":"https:\/\/times.edu.vn\/?p=37979"},"modified":"2026-05-08T17:12:35","modified_gmt":"2026-05-08T10:12:35","slug":"igcse-energy-changes-questions","status":"publish","type":"post","link":"https:\/\/times.edu.vn\/en\/igcse\/igcse-energy-changes-questions\/","title":{"rendered":"IGCSE Chemistry Energy Changes: Exothermic vs Endothermic + Calculations A*"},"content":{"rendered":"<p><strong><a href=\"https:\/\/times.edu.vn\/en\/igcse\/what-is-igcse-a-comprehensive-guide-for-students\/\">IGCSE<\/a><\/strong><strong>\u00a0energy changes questions<\/strong>\u00a0test whether you can explain and calculate heat transfer in reactions using the correct sign for <strong>\u0394H<\/strong>.<\/p>\n<p>You must confidently classify reactions as <strong>exothermic<\/strong>\u00a0or <strong>endothermic<\/strong>, apply <strong>calorimetry<\/strong>\u00a0with q=mc\u0394Tq=mc\u0394T using <strong>specific heat capacity<\/strong>, and interpret reaction profiles to identify <strong>activation energy<\/strong>\u00a0and overall energy change.<\/p>\n<p>High-scoring answers also use <strong>bond breaking<\/strong>\u00a0vs <strong>bond making<\/strong>\u00a0logic and bond energy sums to estimate <strong>enthalpy change<\/strong>.<\/p>\n<p>The key is exam-style method marks: Clear working, correct units (kJ\/mol), and precise chemical language linked to <strong>chemical bonds<\/strong>\u00a0and <strong>reaction kinetics<\/strong>.<\/p>\n<h2><strong>Practice IGCSE Energy Changes Questions And Calculations<\/strong><\/h2>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-38014\" src=\"https:\/\/times.edu.vn\/wp-content\/uploads\/2026\/04\/7-11.webp\" alt=\"IGCSE Energy Changes Questions 2026: How to Tackle Exothermic and Endothermic Topics Step by Step\" width=\"1000\" height=\"558\" srcset=\"https:\/\/times.edu.vn\/wp-content\/uploads\/2026\/04\/7-11.webp 1000w, https:\/\/times.edu.vn\/wp-content\/uploads\/2026\/04\/7-11-300x167.webp 300w, https:\/\/times.edu.vn\/wp-content\/uploads\/2026\/04\/7-11-768x429.webp 768w\" sizes=\"auto, (max-width: 1000px) 100vw, 1000px\" \/><\/p>\n<p>Based on our years of practical tutoring at Times Edu, students score highest on <strong>IGCSE energy changes questions<\/strong>\u00a0when they treat the topic as a <strong>calculation + interpretation<\/strong> unit, not a \u201cdefinition-memorizing\u201d unit.<\/p>\n<p>Examiners reward candidates who can move smoothly between <strong>calorimetry data<\/strong>, <strong>reaction profile diagrams<\/strong>, and <strong>bond energy<\/strong>\u00a0reasoning using consistent sign conventions.<\/p>\n<p>A critical detail most students overlook in the 2026 exam cycle is <strong>method marks<\/strong>: Energy-change questions often allocate marks for the setup, units, substitution, and interpretation, not only the final number.<\/p>\n<p>If your working is inconsistent (especially the <strong>Delta H<\/strong>\u00a0sign), you lose marks even when the magnitude is correct.<\/p>\n<h3><strong>Core exam skill set for IGCSE energy changes questions<\/strong><\/h3>\n<ul>\n<li>Convert words into a model: \u201ctemperature rises\u201d \u2192 <strong>exothermic<\/strong>, \u201ctemperature falls\u201d \u2192 <strong>endothermic<\/strong>.<\/li>\n<li>Apply calorimetry: Q=mc\u0394Tq=mc\u0394T, then connect qq to <strong>enthalpy change<\/strong>\u00a0\u0394H\u0394H.<\/li>\n<li>Interpret reaction profiles: Locate <strong>activation energy<\/strong>\u00a0EaEa\u200b, compare reactants\/products energy, infer sign of \u0394H\u0394H.<\/li>\n<li>Use bond energies: \u0394H=\u2211E(bonds broken)\u2212\u2211E(bonds formed)\u0394H=\u2211E(bonds broken)\u2212\u2211E(bonds formed).<\/li>\n<li>Explain mechanism-level meaning: <strong>B<\/strong><strong>ond breaking<\/strong>\u00a0absorbs energy, <strong>bond making<\/strong>\u00a0releases energy, and <strong>reaction kinetics<\/strong>\u00a0influences how quickly energy is released\/absorbed.<\/li>\n<\/ul>\n<h3><strong>The sign convention that protects your marks<\/strong><\/h3>\n<p>Many students mix up heat flow direction and the sign of \u0394H\u0394H. Use this single rule every time:<\/p>\n<ul>\n<li><strong>Exothermic:<\/strong>\u00a0Products are lower energy than reactants, so \u0394H&lt;0\u0394H&lt;0.<\/li>\n<li><strong>Endothermic:<\/strong>\u00a0Products are higher energy than reactants, so \u0394H&gt;0\u0394H&gt;0.<\/li>\n<\/ul>\n<p>Keep your language aligned with the physics: \u201cheat released to surroundings\u201d means the system loses energy \u2192 negative \u0394H\u0394H.<\/p>\n<h3><strong>What \u201cgrade boundaries\u201d really mean for this topic<\/strong><\/h3>\n<p>Grade boundaries change by paper difficulty and session, so you should not chase a fixed number. What is stable is the marker behaviour: Energy-change questions are designed to separate students who can <strong>justify<\/strong>\u00a0from students who only \u201cplug values.\u201d<\/p>\n<p>The highest bands typically require (1) correct calculations with units, (2) clean diagram interpretation, and (3) a short, precise explanation linking <strong>chemical bonds<\/strong>\u00a0to the sign of <strong>enthalpy change<\/strong>.<\/p>\n<h3><strong>Subject selection strategy for international-school pathways<\/strong><\/h3>\n<p>From our direct experience with international school curricula, students aiming for Chemistry-heavy pathways (Medicine, Engineering, Natural Sciences) should treat Energy Changes as a \u201cmust-master\u201d topic because it connects forward into <strong>reaction kinetics<\/strong>, equilibrium, and energetics in <a href=\"https:\/\/times.edu.vn\/en\/ib\/the-ultimate-ib-diploma-program-ibdp-guide\/\">IB<\/a>\/<a href=\"https:\/\/times.edu.vn\/en\/a-level\/what-is-a-level\/\">A-Level<\/a>.<\/p>\n<p>Students building a business or humanities profile still benefit because strong quantitative Chemistry boosts academic credibility and widens sixth-form subject options.<\/p>\n<p><strong style=\"color: #f00;\">&gt;&gt;&gt; Read more:<\/strong> <a class=\"xem-them-link\" href=\"https:\/\/times.edu.vn\/en\/ib\/igcse-to-ib-skills\/\">IGCSE to IB Skills<\/a> 2026: What Study Habits and Academic Skills Students Need to Succeed<\/p>\n<h2><strong>Identifying Exothermic And Endothermic Reactions<\/strong><\/h2>\n<p>IGCSE energy changes questions often start with a simple prompt: \u201cThe temperature increases\u201d or \u201cThe mixture cools down.\u201d Your job is to translate that observation into an energy model using <strong>enthalpy change<\/strong>\u00a0language.<\/p>\n<h3><strong>Fast identification rules that never fail<\/strong><\/h3>\n<ul>\n<li>If the surroundings warm up, the reaction releases heat \u2192 <strong>exothermic<\/strong>, \u0394H\u0394H is negative.<\/li>\n<li>If the surroundings cool down, the reaction absorbed heat \u2192 <strong>endothermic<\/strong>, \u0394H\u0394H is positive.<\/li>\n<li>If a diagram shows products lower than reactants, it is exothermic even if the word \u201cheat\u201d is not mentioned.<\/li>\n<\/ul>\n<h3><strong>Common misconceptions that cost marks<\/strong><\/h3>\n<p><strong>Misconception 1: \u201cExothermic means temperature always rises a lot.\u201d<\/strong><\/p>\n<ul>\n<li>Temperature change depends on mass, insulation, and <strong>specific heat capacity<\/strong>. A small rise can still be exothermic.<\/li>\n<\/ul>\n<p><strong>Misconception 2: \u201cEndothermic reactions do not happen because they need energy.\u201d<\/strong><\/p>\n<ul>\n<li>They do happen when energy is supplied from surroundings or stored in products. Photosynthesis is the classic example.<\/li>\n<\/ul>\n<p><strong>Misconception 3: \u201cActivation energy equals \u0394H\u0394H.\u201d<\/strong><\/p>\n<ul>\n<li>Activation energy is the barrier height; \u0394H\u0394H is the net difference between reactants and products. They measure different things.<\/li>\n<\/ul>\n<h3><strong>Table: <\/strong><strong>E<\/strong><strong>xam language you must decode quickly<\/strong><\/h3>\n<table>\n<tbody>\n<tr>\n<th colspan=\"1\" rowspan=\"1\"><strong>What the question says<\/strong><\/th>\n<th colspan=\"1\" rowspan=\"1\"><strong>What it implies<\/strong><\/th>\n<th colspan=\"1\" rowspan=\"1\"><strong>What you write<\/strong><\/th>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\">\u201cTemperature increased\u201d<\/td>\n<td colspan=\"1\" rowspan=\"1\">Heat released to surroundings<\/td>\n<td colspan=\"1\" rowspan=\"1\">Exothermic, \u0394H&lt;0\u0394H&lt;0<\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\">\u201cTemperature decreased\u201d<\/td>\n<td colspan=\"1\" rowspan=\"1\">Heat absorbed from surroundings<\/td>\n<td colspan=\"1\" rowspan=\"1\">Endothermic, \u0394H&gt;0\u0394H&gt;0<\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\">\u201cProducts lower energy\u201d<\/td>\n<td colspan=\"1\" rowspan=\"1\">System lost energy overall<\/td>\n<td colspan=\"1\" rowspan=\"1\">Negative \u0394H\u0394H<\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\">\u201cCatalyst used\u201d<\/td>\n<td colspan=\"1\" rowspan=\"1\">Lower EaEa\u200b, faster <strong>reaction kinetics<\/strong><\/td>\n<td colspan=\"1\" rowspan=\"1\">\u0394H\u0394H unchanged<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h3><strong>Practical recognition in typical IGCSE contexts<\/strong><\/h3>\n<ul>\n<li><strong>Neutralization<\/strong>\u00a0is commonly exothermic, so calorimetry data often shows a temperature rise.<\/li>\n<li><strong>Thermal decomposition<\/strong>\u00a0is commonly endothermic, so heating is required and products have higher energy.<\/li>\n<\/ul>\n<p>A critical detail most students overlook in the 2026 exam cycle is that explanations must name the direction of heat transfer. \u201cExothermic because it releases energy\u201d is weaker than \u201cheat is transferred from the reaction mixture to the surroundings, so \u0394H\u0394H is negative.\u201d<\/p>\n<p><strong style=\"color: #f00;\">&gt;&gt;&gt; Read more:<\/strong> <a class=\"xem-them-link\" href=\"https:\/\/times.edu.vn\/en\/igcse\/igcse-motivation-and-study-consistency\/\">IGCSE Motivation and Study Consistency<\/a> 2026: How to Stay Focused and Revise Regularly<\/p>\n<h2><strong>Calculating Bond Energy In Chemical Processes<\/strong><\/h2>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-38018\" src=\"https:\/\/times.edu.vn\/wp-content\/uploads\/2026\/04\/8-12.webp\" alt=\"IGCSE Energy Changes Questions 2026: How to Tackle Exothermic and Endothermic Topics Step by Step\" width=\"1000\" height=\"558\" srcset=\"https:\/\/times.edu.vn\/wp-content\/uploads\/2026\/04\/8-12.webp 1000w, https:\/\/times.edu.vn\/wp-content\/uploads\/2026\/04\/8-12-300x167.webp 300w, https:\/\/times.edu.vn\/wp-content\/uploads\/2026\/04\/8-12-768x429.webp 768w\" sizes=\"auto, (max-width: 1000px) 100vw, 1000px\" \/><\/p>\n<p>Bond-energy questions are a high-yield part of <strong>IGCSE energy changes questions<\/strong>\u00a0because they test conceptual chemistry and arithmetic at the same time. Your score depends on structure: List bonds broken, list bonds formed, then apply the formula with correct signs.<\/p>\n<h3><strong>The exam formula and what it really means<\/strong><\/h3>\n<p>\u0394H=\u2211E(bonds broken)\u2212\u2211E(bonds formed)\u0394H=\u2211E(bonds broken)\u2212\u2211E(bonds formed)<\/p>\n<ul>\n<li><strong>Bond breaking<\/strong>\u00a0needs energy input, so it is treated as positive energy absorbed.<\/li>\n<li><strong>Bond making<\/strong>\u00a0releases energy, so it is treated as energy given out.<\/li>\n<\/ul>\n<p>If the energy released by bond making is larger than the energy absorbed in bond breaking, the result is negative \u0394H\u0394Hand the reaction is exothermic.<\/p>\n<h3><strong>Step-by-step method markers expect<\/strong><\/h3>\n<ol start=\"1\">\n<li><strong>Write the balanced equation.<\/strong><\/li>\n<li><strong>Count each bond type<\/strong>\u00a0on reactants and products.<\/li>\n<li><strong>Multiply<\/strong>\u00a0each bond count by the given bond energy.<\/li>\n<li><strong>Sum bonds broken<\/strong>, sum bonds formed.<\/li>\n<li>Subtract using the correct order and state units (kJ\/mol).<\/li>\n<\/ol>\n<h3><strong>A worked-style template (use this format in your answer)<\/strong><\/h3>\n<p>Bonds broken:<\/p>\n<ul>\n<li>Xx \u00d7 (bond type) = x\u22c5Ex\u22c5E kJ<\/li>\n<li>Total broken = \u2026 KJ<\/li>\n<\/ul>\n<p>Bonds formed:<\/p>\n<ul>\n<li>Yy \u00d7 (bond type) = y\u22c5Ey\u22c5E kJ<\/li>\n<li>Total formed = \u2026 KJ<\/li>\n<\/ul>\n<p>\u0394H=(broken)\u2212(formed)=\u2026\u0394H=(broken)\u2212(formed)=\u2026 KJ\/mol<\/p>\n<p>Interpretation: \u0394H\u0394H negative \u2192 exothermic; positive \u2192 endothermic.<\/p>\n<h3><strong>What examiners are checking conceptually<\/strong><\/h3>\n<p>They are checking whether you understand <strong>chemical bonds<\/strong>\u00a0as energy stores. If products contain stronger (lower-energy) bonds overall, energy is released to form them. If products require weaker (higher-energy) bonding arrangements, energy must be absorbed.<\/p>\n<h3><strong>Common traps in bond energy calculations<\/strong><\/h3>\n<ul>\n<li><strong>Forgetting diatomic molecules<\/strong>\u00a0(e.g., O2O2\u200b, H2H2\u200b, Cl2Cl2\u200b) changes bond counts.<\/li>\n<li><strong>Not balancing before counting<\/strong>\u00a0leads to wrong totals even if your method is correct.<\/li>\n<li><strong>Using the wrong sign logic<\/strong>: Bond energies are positive values, but the subtraction creates the sign of \u0394H\u0394H.<\/li>\n<li><strong>Treating bond energy answers as exact<\/strong>: Bond energies are averaged values, so your number is an estimate. Your interpretation matters as much as the arithmetic.<\/li>\n<\/ul>\n<p>From our direct experience with international school curricula, the best students add one sentence of chemical meaning after the calculation. That sentence often secures the last mark.<\/p>\n<p><strong style=\"color: #f00;\">&gt;&gt;&gt; Read more:<\/strong> <a class=\"xem-them-link\" href=\"https:\/\/times.edu.vn\/en\/igcse\/igcse-subjects-that-keep-doors-open\/\">IGCSE Subjects that Keep Doors Open in<\/a> 2026: How to Choose Flexible Options for Future Study Paths<\/p>\n<h2><strong>Drawing And Interpreting Reaction Profile Diagrams<\/strong><\/h2>\n<p>Reaction profile diagrams appear in many <strong>IGCSE energy changes questions<\/strong>\u00a0because they test understanding of EaEa\u200b, \u0394H\u0394H, and the effect of a catalyst on <strong>reaction kinetics<\/strong>. You are not drawing \u201ca pretty curve,\u201d you are labelling energy relationships.<\/p>\n<h3><strong>What must be on a correct reaction profile<\/strong><\/h3>\n<ul>\n<li>Y-axis labelled <strong>Energy<\/strong>\u00a0(or Enthalpy).<\/li>\n<li>X-axis labelled <strong>Progress of reaction<\/strong>.<\/li>\n<li>Reactants energy level and products energy level clearly shown.<\/li>\n<li>Peak shown for the transition state.<\/li>\n<li><strong>Activation energy<\/strong>\u00a0EaEa\u200b marked from reactants level to the peak.<\/li>\n<li><strong>Delta H<\/strong>\u00a0\u0394H\u0394H marked from reactants to products (up or down).<\/li>\n<\/ul>\n<h3><strong>Table: <\/strong><strong>H<\/strong><strong>ow to read the diagram in one glance<\/strong><\/h3>\n<table>\n<tbody>\n<tr>\n<th colspan=\"1\" rowspan=\"1\"><strong>Diagram feature<\/strong><\/th>\n<th colspan=\"1\" rowspan=\"1\"><strong>Meaning<\/strong><\/th>\n<th colspan=\"1\" rowspan=\"1\"><strong>Exam statement<\/strong><\/th>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\">Peak height above reactants<\/td>\n<td colspan=\"1\" rowspan=\"1\">Activation energy EaEa\u200b<\/td>\n<td colspan=\"1\" rowspan=\"1\">Minimum energy needed for reaction to start<\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\">Products below reactants<\/td>\n<td colspan=\"1\" rowspan=\"1\">Exothermic<\/td>\n<td colspan=\"1\" rowspan=\"1\">\u0394H&lt;0\u0394H&lt;0, energy released<\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\">Products above reactants<\/td>\n<td colspan=\"1\" rowspan=\"1\">Endothermic<\/td>\n<td colspan=\"1\" rowspan=\"1\">\u0394H&gt;0\u0394H&gt;0, energy absorbed<\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\">Lower peak with catalyst<\/td>\n<td colspan=\"1\" rowspan=\"1\">Faster rate<\/td>\n<td colspan=\"1\" rowspan=\"1\">Catalyst lowers EaEa\u200b, \u0394H\u0394H unchanged<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h3><strong>The catalyst principle you must state correctly<\/strong><\/h3>\n<p>A catalyst provides an alternative pathway with lower activation energy. It speeds up reaction rate (reaction kinetics) because more particles have energy above EaEa\u200b at the same temperature. It does not change the energies of reactants or products, so it does not change \u0394H\u0394H.<\/p>\n<h3><strong>Common misconceptions in diagrams<\/strong><\/h3>\n<p><strong>Misconception 1: \u201cCatalyst reduces \u0394H\u0394H.\u201d<\/strong><\/p>\n<ul>\n<li>No. The vertical gap between reactants and products stays identical.<\/li>\n<\/ul>\n<p><strong>Misconception 2: \u201cActivation energy is the difference between reactants and products.\u201d<\/strong><\/p>\n<ul>\n<li>That difference is \u0394H\u0394H. Activation energy is reactants to peak.<\/li>\n<\/ul>\n<p><strong>Misconception 3: \u201cEndothermic reactions have no activation energy.\u201d<\/strong><\/p>\n<ul>\n<li>Every reaction needs EaEa\u200b, even if it absorbs energy overall.<\/li>\n<\/ul>\n<p>The pedagogical approach we recommend for high-achievers is to practise drawing the diagram from memory in under 30 seconds, then spend your time on correct labels and interpretation sentences. That is how you protect marks under timed conditions.<\/p>\n<p><strong style=\"color: #f00;\">&gt;&gt;&gt; Read more:<\/strong> <a class=\"xem-them-link\" href=\"https:\/\/times.edu.vn\/en\/igcse\/igcse-topic-past-papers\/\">IGCSE Topic Past Papers<\/a> 2026: How to Use Targeted Practice to Improve Faster<\/p>\n<h2><strong>Frequently Asked Questions<\/strong><\/h2>\n<div class=\"hoi-dap-thok-new low-faq\">\n<div class=\"thong-tin-dai\">\n<p class=\"tit-dai\"><strong>How do you calculate energy change in IGCSE Chemistry?<\/strong><\/p>\n<div class=\"chi-tiet-thong-tin\">\n<p>In calorimetry-style IGCSE energy changes questions, start with q=mc\u0394Tq=mc\u0394T, where mm is mass, cc is <strong>specific heat capacity<\/strong>, and \u0394T\u0394T is temperature change.Then convert heat qq into an enthalpy change per mole by dividing by moles of the limiting reactant, and use the correct sign for \u0394H\u0394H.<\/p>\n<p>State units clearly, usually kJ\/mol, and explain whether the result is exothermic or endothermic.<\/p>\n<\/div>\n<\/div>\n<div class=\"thong-tin-dai\">\n<p class=\"tit-dai\"><strong>What is the difference between exothermic and endothermic reactions?<\/strong><\/p>\n<div class=\"chi-tiet-thong-tin\">\n<p>Exothermic reactions transfer heat from the system to the surroundings, so temperature of the surroundings increases and \u0394H\u0394H is negative.Endothermic reactions absorb heat from the surroundings into the system, so the surroundings cool and \u0394H\u0394H is positive.<\/p>\n<p>In reaction profile terms, products are lower than reactants for exothermic reactions, and higher for endothermic reactions.<\/p>\n<\/div>\n<\/div>\n<div class=\"thong-tin-dai\">\n<p class=\"tit-dai\"><strong>Is bond breaking an endothermic or exothermic process?<\/strong><\/p>\n<div class=\"chi-tiet-thong-tin\">\n<p><strong>Bond breaking<\/strong>\u00a0is endothermic because energy must be absorbed to overcome attractions in <strong>chemical bonds<\/strong>.<strong>Bond making<\/strong>\u00a0is exothermic because energy is released when new bonds form and the system moves to a lower-energy arrangement.<\/p>\n<p>This is the core idea behind bond-energy calculations for <strong>enthalpy change<\/strong>.<\/p>\n<\/div>\n<\/div>\n<div class=\"thong-tin-dai\">\n<p class=\"tit-dai\"><strong>How do you draw a reaction profile for an exothermic reaction?<\/strong><\/p>\n<div class=\"chi-tiet-thong-tin\">\n<p>Draw energy on the y-axis and reaction progress on the x-axis, then place reactants at a higher energy level than products.Add a single peak for the transition state, label the vertical distance from reactants to the peak as <strong>activation energy<\/strong>\u00a0EaEa\u200b, and label the drop from reactants to products as negative <strong>Delta H<\/strong>\u00a0\u0394H\u0394H. Include clear axis labels and keep the diagram clean and proportional.<\/p>\n<\/div>\n<\/div>\n<div class=\"thong-tin-dai\">\n<p class=\"tit-dai\"><strong>What does activation energy represent in a diagram?<\/strong><\/p>\n<div class=\"chi-tiet-thong-tin\">\n<p>Activation energy is the minimum energy needed for reacting particles to form the activated complex and start converting reactants into products. On a reaction profile, it is the vertical energy gap from reactants to the peak.Lowering activation energy (for example with a catalyst) increases rate because it changes <strong>reaction kinetics<\/strong>\u00a0without changing \u0394H\u0394H.<\/p>\n<\/div>\n<\/div>\n<div class=\"thong-tin-dai\">\n<p class=\"tit-dai\"><strong>How do you use bond energy values to find enthalpy change?<\/strong><\/p>\n<div class=\"chi-tiet-thong-tin\">List and total the energies of bonds broken in the reactants, then list and total the energies of bonds formed in the products. Apply \u0394H=\u2211E(broken)\u2212\u2211E(formed)\u0394H=\u2211E(broken)\u2212\u2211E(formed) and report the result in kJ\/mol. If the result is negative, the reaction is exothermic; if positive, it is endothermic.<\/div>\n<\/div>\n<div class=\"thong-tin-dai\">\n<p class=\"tit-dai\"><strong>What are examples of energy changes in everyday life?<\/strong><\/p>\n<div class=\"chi-tiet-thong-tin\">\n<p>Combustion in fuels is exothermic, releasing heat and light, while instant cold packs are endothermic because dissolving certain salts absorbs heat from your hand.Cooking often involves endothermic processes because energy is absorbed to drive physical and chemical changes in food. These real examples help you explain heat transfer clearly in IGCSE energy changes questions.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<h4>Conclusion<\/h4>\n<p>Based on our years of practical tutoring at <a href=\"https:\/\/times.edu.vn\/en\/\">Times Edu<\/a>, students improve fastest when we diagnose the exact failure point: Sign errors in \u0394H\u0394H, weak diagram labelling of EaEa\u200b, or messy calorimetry setups that lose method marks. We then drill exam-standard routines until they are automatic, so performance stays stable under pressure.<\/p>\n<p>If you want a personalized study route, we can map (1) your current topic gaps, (2) your target grade and subject pathway, and (3) the most efficient practice sequence for your exam board.<\/p>\n<p>Contact Times Edu to book a 1\u20131 academic consultation and receive a tailored plan for mastering <strong>IGCSE energy changes questions<\/strong>, including mixed practice across calorimetry, bond energies, and reaction profiles.<\/p>\n\n\n<div class=\"kk-star-ratings kksr-auto kksr-align-right kksr-valign-bottom\"\n    data-payload='{&quot;align&quot;:&quot;right&quot;,&quot;id&quot;:&quot;37979&quot;,&quot;slug&quot;:&quot;default&quot;,&quot;valign&quot;:&quot;bottom&quot;,&quot;ignore&quot;:&quot;&quot;,&quot;reference&quot;:&quot;auto&quot;,&quot;class&quot;:&quot;&quot;,&quot;count&quot;:&quot;1&quot;,&quot;legendonly&quot;:&quot;&quot;,&quot;readonly&quot;:&quot;&quot;,&quot;score&quot;:&quot;5&quot;,&quot;starsonly&quot;:&quot;&quot;,&quot;best&quot;:&quot;5&quot;,&quot;gap&quot;:&quot;5&quot;,&quot;greet&quot;:&quot;\u0110\u00e1nh gi\u00e1 b\u00e0i vi\u1ebft&quot;,&quot;legend&quot;:&quot;5\\\/5 - (1 vote)&quot;,&quot;size&quot;:&quot;24&quot;,&quot;title&quot;:&quot;IGCSE Chemistry Energy Changes: Exothermic vs Endothermic + Calculations A*&quot;,&quot;width&quot;:&quot;142.5&quot;,&quot;_legend&quot;:&quot;{score}\\\/{best} - ({count} {votes})&quot;,&quot;font_factor&quot;:&quot;1.25&quot;}'>\n            \n<div class=\"kksr-stars\">\n    \n<div class=\"kksr-stars-inactive\">\n            <div class=\"kksr-star\" data-star=\"1\" style=\"padding-right: 5px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n            <div class=\"kksr-star\" data-star=\"2\" style=\"padding-right: 5px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n            <div class=\"kksr-star\" data-star=\"3\" style=\"padding-right: 5px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n            <div class=\"kksr-star\" data-star=\"4\" style=\"padding-right: 5px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n            <div class=\"kksr-star\" data-star=\"5\" style=\"padding-right: 5px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n    <\/div>\n    \n<div class=\"kksr-stars-active\" style=\"width: 142.5px;\">\n            <div class=\"kksr-star\" style=\"padding-right: 5px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n            <div class=\"kksr-star\" style=\"padding-right: 5px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n            <div class=\"kksr-star\" style=\"padding-right: 5px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n            <div class=\"kksr-star\" style=\"padding-right: 5px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n            <div class=\"kksr-star\" style=\"padding-right: 5px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n    <\/div>\n<\/div>\n                \n\n<div class=\"kksr-legend\" style=\"font-size: 19.2px;\">\n            5\/5 - (1 vote)    <\/div>\n    <\/div>\n","protected":false},"excerpt":{"rendered":"<p>IGCSE\u00a0energy changes questions\u00a0test whether you can explain and calculate heat transfer in reactions using the correct sign for \u0394H. You must confidently classify reactions as exothermic\u00a0or endothermic, apply calorimetry\u00a0with q=mc\u0394Tq=mc\u0394T using specific heat capacity, and interpret reaction profiles to identify activation energy\u00a0and overall energy change. High-scoring answers also use bond breaking\u00a0vs bond making\u00a0logic and bond &#8230; <a title=\"IGCSE Chemistry Energy Changes: Exothermic vs Endothermic + Calculations A*\" class=\"read-more\" href=\"https:\/\/times.edu.vn\/en\/igcse\/igcse-energy-changes-questions\/\" aria-label=\"Read more about IGCSE Chemistry Energy Changes: Exothermic vs Endothermic + Calculations A*\">Read more<\/a><\/p>\n","protected":false},"author":7,"featured_media":37981,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"content-type":"","rank_math_title":"","rank_math_description":"IGCSE Chemistry energy changes (Topic 6): exothermic vs endothermic, energy profile diagrams, bond energy calculations, \u0394H formula. Worked examples for Paper 4 Extended A*.","footnotes":""},"categories":[166],"tags":[],"class_list":["post-37979","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-igcse"],"_links":{"self":[{"href":"https:\/\/times.edu.vn\/en\/wp-json\/wp\/v2\/posts\/37979","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/times.edu.vn\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/times.edu.vn\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/times.edu.vn\/en\/wp-json\/wp\/v2\/users\/7"}],"replies":[{"embeddable":true,"href":"https:\/\/times.edu.vn\/en\/wp-json\/wp\/v2\/comments?post=37979"}],"version-history":[{"count":4,"href":"https:\/\/times.edu.vn\/en\/wp-json\/wp\/v2\/posts\/37979\/revisions"}],"predecessor-version":[{"id":39656,"href":"https:\/\/times.edu.vn\/en\/wp-json\/wp\/v2\/posts\/37979\/revisions\/39656"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/times.edu.vn\/en\/wp-json\/wp\/v2\/media\/37981"}],"wp:attachment":[{"href":"https:\/\/times.edu.vn\/en\/wp-json\/wp\/v2\/media?parent=37979"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/times.edu.vn\/en\/wp-json\/wp\/v2\/categories?post=37979"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/times.edu.vn\/en\/wp-json\/wp\/v2\/tags?post=37979"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}