<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="4:3">
  <title>Energy in Reversible Reactions</title>
  <style>
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      justify-content: space-between;
      gap: 8px;
      margin: 4px 0;
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    .substance-card {
      flex: 0 0 105px;
      background: #f8fafc;
      border: 2px solid #e2e8f0;
      border-radius: 12px;
      padding: 14px 6px;
      text-align: center;
      box-shadow: 0 1px 3px rgba(0,0,0,0.04);
      transition: border-color 0.3s;
    }

    .substance-card .formula {
      font-size: 17px;
      font-weight: 800;
      color: #0f172a;
      line-height: 1.2;
    }

    .substance-card .role {
      font-size: 11px;
      font-weight: 600;
      color: #64748b;
      margin-top: 4px;
      text-transform: uppercase;
      letter-spacing: 0.04em;
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    /* Pathways */
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      flex-direction: column;
      gap: 12px;
      min-width: 140px;
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    /* Forward (Exothermic) */
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      font-size: 12px;
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      height: 6px;
      border-radius: 3px;
      position: relative;
    }

    .forward .arrow-track {
      background: #fed7aa;
    }

    .reverse .arrow-track {
      background: #bae6fd;
    }

    .arrow-track::after {
      content: "";
      position: absolute;
      top: -3px;
      width: 0;
      height: 0;
      border-top: 6px solid transparent;
      border-bottom: 6px solid transparent;
    }

    .forward .arrow-track::after {
      right: -2px;
      border-left: 8px solid #ea580c;
    }

    .reverse .arrow-track::after {
      left: -2px;
      border-right: 8px solid #0284c7;
    }

    .action-note {
      font-size: 11px;
      font-weight: 600;
      display: flex;
      align-items: center;
      gap: 4px;
    }

    .forward .action-note { color: #9a3412; }
    .reverse .action-note { color: #075985; }

    /* Comparison Key */
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      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 8px;
      margin-top: 8px;
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    .comp-card {
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      gap: 4px;
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    .comp-value {
      font-size: 13px;
      font-weight: 800;
      color: #0f172a;
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    .comp-tags {
      display: flex;
      justify-content: center;
      gap: 4px;
      margin-top: 3px;
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    .tag {
      font-size: 11px;
      font-weight: 700;
      padding: 2px 6px;
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      background: #e0f2fe;
      color: #0369a1;
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        padding: 10px 4px;
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        font-size: 11px;
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        font-size: 12px;
      }
      .action-note {
        font-size: 10px;
      }
    }
  </style>
</head>
<body>

  
  <div class="header">
    <div class="title-badge">Energy in Reversible Reactions</div>
  </div>

  
  <div class="btn-group">
    <button class="tab-btn active" onclick="setMode('both')">Both Directions</button>
    <button class="tab-btn" onclick="setMode('forward')">Forward (Exothermic)</button>
    <button class="tab-btn" onclick="setMode('reverse')">Reverse (Endothermic)</button>
  </div>

  
  <div class="reaction-stage">
    
    <div class="substance-card" id="leftCard">
      <div class="formula">N₂ + 3H₂</div>
      <div class="role">Reactants</div>
    </div>

    
    <div class="pathways-container">
      
      
      <div class="pathway forward" id="forwardPath" onclick="setMode('forward')">
        <div class="pathway-row">
          <span class="label">Forward: Exothermic</span>
          <span class="val">ΔH = −92 kJ/mol</span>
        </div>
        <div class="arrow-track"></div>
        <div class="action-note">
          <span>🔥</span> Releases heat to surroundings
        </div>
      </div>

      
      <div class="pathway reverse" id="reversePath" onclick="setMode('reverse')">
        <div class="pathway-row">
          <span class="label">Reverse: Endothermic</span>
          <span class="val">ΔH = +92 kJ/mol</span>
        </div>
        <div class="arrow-track"></div>
        <div class="action-note">
          <span>❄️</span> Absorbs heat from surroundings
        </div>
      </div>

    </div>

    
    <div class="substance-card" id="rightCard">
      <div class="formula">2NH₃</div>
      <div class="role">Products</div>
    </div>
  </div>

  
  <div class="comparison-grid">
    <div class="comp-card">
      <div class="comp-title">⚖️ Same Magnitude</div>
      <div class="comp-value">|−92| = |+92| = 92 kJ</div>
    </div>
    <div class="comp-card">
      <div class="comp-title">⇄ Opposite Signs</div>
      <div class="comp-tags">
        <span class="tag tag-exo">(−) Out</span>
        <span class="tag tag-endo">(+) In</span>
      </div>
    </div>
  </div>

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</body>
</html>

Identifying Exothermic and Endothermic Directions in Equilibria

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="4:3">
  <title>Equilibrium Energy Directions</title>
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
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      display: flex;
      flex-direction: column;
      gap: 12px;
      user-select: none;
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    /* Direction filter tabs */
    .controls {
      display: flex;
      justify-content: center;
      gap: 6px;
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      margin: 0 auto;
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      padding: 6px 14px;
      font-size: 13px;
      font-weight: 600;
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      border-radius: 7px;
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      transition: all 0.2s ease;
    }
    .filter-btn.active {
      background: #ffffff;
      color: #1e2945;
      box-shadow: 0 1px 4px rgba(0,0,0,0.08);
    }

    /* Equation Cards */
    .cards-grid {
      display: flex;
      flex-direction: column;
      gap: 10px;
    }
    .eq-card {
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 12px;
      padding: 12px 14px;
      box-shadow: 0 1px 3px rgba(0,0,0,0.04);
      display: flex;
      flex-direction: column;
      gap: 8px;
    }

    /* Chemical equation bar */
    .eq-display {
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 18px;
      font-weight: 700;
      letter-spacing: 0.5px;
      color: #1e2945;
      gap: 8px;
      padding: 6px 0;
      border-bottom: 1px dashed #e2e8f0;
    }
    .heat-tag {
      display: inline-flex;
      align-items: center;
      gap: 4px;
      padding: 2px 8px;
      border-radius: 6px;
      font-size: 14px;
      font-weight: 700;
    }
    .heat-tag.product {
      background: #ffedd5;
      color: #c2410c;
      border: 1px solid #fdba74;
    }
    .heat-tag.reactant {
      background: #e0f2fe;
      color: #0369a1;
      border: 1px solid #7dd3fc;
    }

    /* Arrow tracks */
    .direction-rows {
      display: flex;
      flex-direction: column;
      gap: 6px;
    }
    .dir-row {
      display: grid;
      grid-template-columns: 80px 1fr;
      align-items: center;
      gap: 10px;
      padding: 6px 10px;
      border-radius: 8px;
      transition: opacity 0.25s ease, background 0.25s ease;
      cursor: pointer;
    }
    .dir-row:hover {
      background: #f8fafc;
    }
    .dir-row.dimmed {
      opacity: 0.25;
    }

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      display: flex;
      align-items: center;
      justify-content: center;
      gap: 6px;
      font-size: 12px;
      font-weight: 700;
      padding: 4px 8px;
      border-radius: 6px;
    }
    .arrow-badge.exo {
      background: #ea580c;
      color: #ffffff;
    }
    .arrow-badge.endo {
      background: #0284c7;
      color: #ffffff;
    }

    /* Label text */
    .dir-label {
      font-size: 13px;
      font-weight: 600;
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 6px;
    }
    .type-tag {
      font-size: 11px;
      font-weight: 600;
      padding: 2px 6px;
      border-radius: 4px;
    }
    .type-tag.exo-sub {
      background: #fff7ed;
      color: #ea580c;
    }
    .type-tag.endo-sub {
      background: #f0f9ff;
      color: #0284c7;
    }

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      .dir-row { grid-template-columns: 75px 1fr; padding: 5px 6px; }
      .dir-label { font-size: 12px; }
      .type-tag { font-size: 10px; }
    }
  </style>
</head>
<body>

  
  <div class="controls" role="tablist">
    <button class="filter-btn active" data-filter="all">All Directions</button>
    <button class="filter-btn" data-filter="forward">Forward (→)</button>
    <button class="filter-btn" data-filter="reverse">Reverse (←)</button>
  </div>

  <div class="cards-grid">
    
    <div class="eq-card">
      <div class="eq-display">
        <span>A + B</span>
        <span style="color: #64748b; font-weight: 500;">⇌</span>
        <span>C +</span>
        <span class="heat-tag product">🔥 Heat</span>
      </div>
      <div class="direction-rows">
        <div class="dir-row" data-dir="forward">
          <div class="arrow-badge exo">Forward →</div>
          <div class="dir-label">
            <span style="color: #ea580c;">Exothermic</span>
            <span class="type-tag exo-sub">Produces Heat</span>
          </div>
        </div>
        <div class="dir-row" data-dir="reverse">
          <div class="arrow-badge endo">← Reverse</div>
          <div class="dir-label">
            <span style="color: #0284c7;">Endothermic</span>
            <span class="type-tag endo-sub">Absorbs Heat</span>
          </div>
        </div>
      </div>
    </div>

    
    <div class="eq-card">
      <div class="eq-display">
        <span>A +</span>
        <span class="heat-tag reactant">❄️ Heat</span>
        <span style="color: #64748b; font-weight: 500;">⇌</span>
        <span>B</span>
      </div>
      <div class="direction-rows">
        <div class="dir-row" data-dir="forward">
          <div class="arrow-badge endo">Forward →</div>
          <div class="dir-label">
            <span style="color: #0284c7;">Endothermic</span>
            <span class="type-tag endo-sub">Consumes Heat</span>
          </div>
        </div>
        <div class="dir-row" data-dir="reverse">
          <div class="arrow-badge exo">← Reverse</div>
          <div class="dir-label">
            <span style="color: #ea580c;">Exothermic</span>
            <span class="type-tag exo-sub">Releases Heat</span>
          </div>
        </div>
      </div>
    </div>
  </div>

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</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="4:3">
  <title>Exothermic vs Endothermic Enthalpy</title>
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
    }
    body {
      width: 100%;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
      color: #1e2945;
      background: transparent;
      padding: 12px;
      display: flex;
      flex-direction: column;
      gap: 12px;
    }

    .grid-container {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 12px;
      width: 100%;
    }

    @media (max-width: 480px) {
      .grid-container {
        grid-template-columns: 1fr;
      }
    }

    .reaction-card {
      background: #ffffff;
      border: 1.5px solid #e2e8f0;
      border-radius: 12px;
      padding: 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      position: relative;
      overflow: hidden;
      cursor: pointer;
      transition: box-shadow 0.2s ease, border-color 0.2s ease;
    }

    .reaction-card:focus,
    .reaction-card.active {
      box-shadow: 0 4px 12px rgba(30, 41, 69, 0.08);
    }

    .card-exo {
      border-color: #fdba74;
    }
    .card-exo.active {
      border-color: #ea580c;
    }

    .card-endo {
      border-color: #93c5fd;
    }
    .card-endo.active {
      border-color: #0284c7;
    }

    .card-header {
      display: flex;
      align-items: center;
      justify-content: space-between;
      width: 100%;
      margin-bottom: 6px;
    }

    .card-title {
      font-size: 15px;
      font-weight: 700;
      display: flex;
      align-items: center;
      gap: 6px;
    }

    .title-exo { color: #c2410c; }
    .title-endo { color: #0369a1; }

    .delta-badge {
      font-size: 13px;
      font-weight: 700;
      padding: 2px 8px;
      border-radius: 6px;
    }
    .badge-exo { background: #ffedd5; color: #c2410c; }
    .badge-endo { background: #e0f2fe; color: #0369a1; }

    .diagram-svg {
      width: 100%;
      height: 180px;
      overflow: visible;
    }

    .energy-level {
      stroke-width: 3;
      stroke-linecap: round;
    }

    .label-text {
      font-size: 11px;
      font-weight: 600;
      fill: #475569;
    }

    .val-text {
      font-size: 13px;
      font-weight: 700;
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    .heat-arrow {
      stroke-dasharray: 6 3;
      animation: heatFlow 2s linear infinite;
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    @keyframes heatFlow {
      to {
        stroke-dashoffset: -18;
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    .heat-banner {
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      text-align: center;
      font-size: 12px;
      font-weight: 700;
      padding: 6px;
      border-radius: 8px;
      margin-top: 6px;
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    .banner-exo {
      background: #fff7ed;
      color: #9a3412;
      border: 1px solid #ffedd5;
    }

    .banner-endo {
      background: #f0f9ff;
      color: #075985;
      border: 1px solid #e0f2fe;
    }

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      display: flex;
      justify-content: center;
      gap: 8px;
    }

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      background: #f1f5f9;
      border: 1px solid #cbd5e1;
      color: #1e2945;
      padding: 6px 14px;
      border-radius: 8px;
      font-size: 13px;
      font-weight: 600;
      cursor: pointer;
      transition: background 0.15s ease, border-color 0.15s ease;
    }

    .btn-toggle.active {
      background: #1e2945;
      color: #ffffff;
      border-color: #1e2945;
    }
  </style>
</head>
<body>

  <div class="controls">
    <button class="btn-toggle active" id="btnBoth" onclick="showMode('both')">Compare Both</button>
    <button class="btn-toggle" id="btnExo" onclick="showMode('exo')">Exothermic (−ΔH)</button>
    <button class="btn-toggle" id="btnEndo" onclick="showMode('endo')">Endothermic (+ΔH)</button>
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  <div class="grid-container">
    
    <div class="reaction-card card-exo active" id="cardExo" onclick="showMode('exo')">
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        <span class="card-title title-exo">🔥 Exothermic</span>
        <span class="delta-badge badge-exo">−ΔH</span>
      </div>

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        <button class="tab-btn" data-step="h2">2. Hydrogen Stream</button>
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The Haber Process: Equation, Reactants, and Catalyst

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    .text-h {
      fill: #334155;
      font-size: 9px;
    }

    .bond {
      stroke: #64748b;
      stroke-width: 2;
      stroke-linecap: round;
    }

    /* Atom Count Checker */
    .balance-box {
      background: #f8f9fa;
      border: 1px solid #e2e8f0;
      border-radius: 10px;
      padding: 8px 12px;
      display: flex;
      flex-direction: column;
      gap: 6px;
    }

    .balance-row {
      display: flex;
      justify-content: space-between;
      align-items: center;
      padding: 4px 8px;
      border-radius: 6px;
      cursor: pointer;
      transition: background-color 0.2s ease;
      font-size: 13px;
      font-weight: 600;
    }

    .balance-row:hover, .balance-row.active {
      background: #e2e8f0;
    }

    .count-tag {
      display: inline-flex;
      align-items: center;
      gap: 6px;
    }

    .dot {
      width: 10px;
      height: 10px;
      border-radius: 50%;
      display: inline-block;
    }

    .dot-n {
      background: #1e3a8a;
    }

    .dot-h {
      background: #ffffff;
      border: 1.5px solid #94a3b8;
    }

    .status-check {
      color: #16a34a;
      font-weight: 700;
      font-size: 14px;
    }

    /* Highlight effects */
    .highlight-n .atom-n {
      filter: drop-shadow(0 0 5px #3b82f6);
    }

    .highlight-h .atom-h {
      filter: drop-shadow(0 0 4px #0ea5e9);
      stroke: #0284c7;
      stroke-width: 2;
    }

    @media (max-width: 420px) {
      .main-grid {
        grid-template-columns: 1fr;
        gap: 8px;
      }
      .center-column {
        flex-direction: row;
        justify-content: center;
        gap: 12px;
      }
      .arrow-symbol {
        transform: rotate(90deg);
      }
      .mol-card {
        min-height: 125px;
      }
      .mol-svg {
        height: 110px;
      }
    }
  </style>
</head>
<body>

  
  <div class="equation-header">
    <span>N<span class="sub">2</span></span>
    <span>+</span>
    <span>3H<span class="sub">2</span></span>
    <span style="color:#64748b;">⇌</span>
    <span>2NH<span class="sub">3</span></span>
  </div>

  
  <div class="main-grid" id="diagramArea">
    
    
    <div class="mol-card">
      <div class="card-title">Reactants</div>
      <svg class="mol-svg" viewBox="0 0 150 140">
        
        <g transform="translate(75, 28)">
          <line x1="-18" y1="-3" x2="18" y2="-3" class="bond" />
          <line x1="-18" y1="0" x2="18" y2="0" class="bond" />
          <line x1="-18" y1="3" x2="18" y2="3" class="bond" />
          <circle cx="-18" cy="0" r="12" class="atom-n" />
          <text x="-18" y="0" class="atom-text text-n">N</text>
          <circle cx="18" cy="0" r="12" class="atom-n" />
          <text x="18" y="0" class="atom-text text-n">N</text>
        </g>

        
        
        <g transform="translate(30, 80)">
          <line x1="-10" y1="0" x2="10" y2="0" class="bond" />
          <circle cx="-10" cy="0" r="8" class="atom-h" />
          <text x="-10" y="0" class="atom-text text-h">H</text>
          <circle cx="10" cy="0" r="8" class="atom-h" />
          <text x="10" y="0" class="atom-text text-h">H</text>
        </g>
        
        <g transform="translate(120, 80)">
          <line x1="-10" y1="0" x2="10" y2="0" class="bond" />
          <circle cx="-10" cy="0" r="8" class="atom-h" />
          <text x="-10" y="0" class="atom-text text-h">H</text>
          <circle cx="10" cy="0" r="8" class="atom-h" />
          <text x="10" y="0" class="atom-text text-h">H</text>
        </g>
        
        <g transform="translate(75, 118)">
          <line x1="-10" y1="0" x2="10" y2="0" class="bond" />
          <circle cx="-10" cy="0" r="8" class="atom-h" />
          <text x="-10" y="0" class="atom-text text-h">H</text>
          <circle cx="10" cy="0" r="8" class="atom-h" />
          <text x="10" y="0" class="atom-text text-h">H</text>
        </g>
      </svg>
    </div>

    
    <div class="center-column">
      <div class="arrow-symbol">⇌</div>
      <div class="badge-exo">Exothermic<br><span style="font-size:9.5px;font-weight:600;opacity:0.9;">Releases Heat</span></div>
    </div>

    
    <div class="mol-card">
      <div class="card-title">Products</div>
      <svg class="mol-svg" viewBox="0 0 150 140">
        
        <g transform="translate(75, 36)">
          <line x1="0" y1="-2" x2="-22" y2="18" class="bond" />
          <line x1="0" y1="-2" x2="0" y2="24" class="bond" />
          <line x1="0" y1="-2" x2="22" y2="18" class="bond" />
          
          <circle cx="-22" cy="18" r="7.5" class="atom-h" />
          <text x="-22" y="18" class="atom-text text-h">H</text>
          
          <circle cx="0" cy="24" r="7.5" class="atom-h" />
          <text x="0" y="24" class="atom-text text-h">H</text>
          
          <circle cx="22" cy="18" r="7.5" class="atom-h" />
          <text x="22" y="18" class="atom-text text-h">H</text>

          <circle cx="0" cy="-6" r="12" class="atom-n" />
          <text x="0" y="-6" class="atom-text text-n">N</text>
        </g>

        
        <g transform="translate(75, 98)">
          <line x1="0" y1="-2" x2="-22" y2="18" class="bond" />
          <line x1="0" y1="-2" x2="0" y2="24" class="bond" />
          <line x1="0" y1="-2" x2="22" y2="18" class="bond" />
          
          <circle cx="-22" cy="18" r="7.5" class="atom-h" />
          <text x="-22" y="18" class="atom-text text-h">H</text>
          
          <circle cx="0" cy="24" r="7.5" class="atom-h" />
          <text x="0" y="24" class="atom-text text-h">H</text>
          
          <circle cx="22" cy="18" r="7.5" class="atom-h" />
          <text x="22" y="18" class="atom-text text-h">H</text>

          <circle cx="0" cy="-6" r="12" class="atom-n" />
          <text x="0" y="-6" class="atom-text text-n">N</text>
        </g>
      </svg>
    </div>

  </div>

  
  <div class="balance-box">
    <div class="balance-row" id="rowN">
      <span class="count-tag">
        <span class="dot dot-n"></span>
        <span>2 Nitrogen atoms</span>
      </span>
      <span>=</span>
      <span class="count-tag">
        <span>2 Nitrogen atoms</span>
        <span class="status-check">✓</span>
      </span>
    </div>
    <div class="balance-row" id="rowH">
      <span class="count-tag">
        <span class="dot dot-h"></span>
        <span>6 Hydrogen atoms</span>
      </span>
      <span>=</span>
      <span class="count-tag">
        <span>6 Hydrogen atoms</span>
        <span class="status-check">✓</span>
      </span>
    </div>
  </div>

  <script>
    const diagram = document.getElementById('diagramArea');
    const rowN = document.getElementById('rowN');
    const rowH = document.getElementById('rowH');

    function toggleHighlight(type) {
      if (type === 'n') {
        const active = diagram.classList.toggle('highlight-n');
        diagram.classList.remove('highlight-h');
        rowN.classList.toggle('active', active);
        rowH.classList.remove('active');
      } else if (type === 'h') {
        const active = diagram.classList.toggle('highlight-h');
        diagram.classList.remove('highlight-n');
        rowH.classList.toggle('active', active);
        rowN.classList.remove('active');
      }
    }

    rowN.addEventListener('click', () => toggleHighlight('n'));
    rowH.addEventListener('click', () => toggleHighlight('h'));

    document.querySelectorAll('.atom-n').forEach(el => {
      el.addEventListener('click', (e) => {
        e.stopPropagation();
        toggleHighlight('n');
      });
    });

    document.querySelectorAll('.atom-h').forEach(el => {
      el.addEventListener('click', (e) => {
        e.stopPropagation();
        toggleHighlight('h');
      });
    });
  </script>
</body>
</html>

UK-GCSE-SCIENCE-CHEM-RC-02-01

Aligned learning resources

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