IP Chemistry Upper Sec 09: Chemical Energetics

For Integrated Programme students: Your current school materials, teacher instructions, and assessment scope take precedence because IP topic sequence and depth vary by school. This is an Eclat IP guide, not the O-Level / SEC G3 exam-track guide.

The core idea is simple: Energetics asks whether heat is released or absorbed.

Use it as a working check: Exothermic reactions have products lower in energy and negative enthalpy change. Endothermic reactions have products higher in energy and positive enthalpy change.

Then go one layer deeper: Example: bond breaking absorbs energy and bond making releases energy. A reaction is exothermic when making new bonds releases more energy than breaking old bonds absorbs.

How this chapter applies

• Eclat core: exothermic and endothermic change, enthalpy sign, energy profiles, activation energy, and the energy cost of bond breaking versus the energy release of bond making form the main route.
• School-sensitive extension: calorimetry, molar enthalpy calculations, Hess cycles, lattice and hydration ideas, and numerical average-bond-energy calculations should be used only where the current school teaches them.
• 2027 national comparison: K324 Topic C9 covers enthalpy signs, energy profiles, activation energy, and qualitative explanation using covalent bond breaking and making.
• Check your school: sign conventions, profile-diagram labels, supplied data, and the required calculation depth can differ. Use the convention in the current school materials.
• Exam-track route: use the separate O-Level and SEC G3 Chemistry notes for K324 topic ownership.

What you must know

• Enthalpy change is heat change at constant pressure; exothermic releases heat (ΔH < 0), endothermic absorbs heat (ΔH > 0).
• Energy profile diagrams must show relative energy of reactants/products, activation energy peak, and ΔH arrow.
• Bond breaking is endothermic; bond making is exothermic; overall ΔH is “energy to break − energy released making.”
• Qualitative bond-energy comparisons explain why combustion is strongly exothermic and why thermal decompositions need heating.

Use this checkpoint before drawing or explaining an energy profile.