Understanding Enthalpy and Thermochemical Equations

Section role: supports the formalization phase in Section 3, building directly on the student data from Section 2 and preparing them for the individual assessment in Section 4. Slides: (1) Title — 'Enthalpy: The Heat Content of Systems'; (2) Defining Enthalpy — bullets: H symbol, constant pressure assumption, why we measure changes (ΔH) rather than absolute values; (3) Exothermic vs Endothermic — bullets: ΔH < 0 for heat release, ΔH > 0 for heat absorption, connection to hand warmers and cold packs from Section 1; (4) The First Law in Action — bullets: q_system = -q_surroundings, energy transfer mechanics; (5) Latent Heat and Temperature Plateaus — bullets: energy input during phase changes without temperature rise, bonding energy; (6) Thermochemical Equations — bullets: writing enthalpy changes directly into balanced equations like CH4 + 2O2 -> CO2 + 2H2O + 890kJ; (7) Reaction Coordinate Diagrams — visual of potential energy versus reaction progress for both endothermic and exothermic pathways; (8) Mind Map Overview — connecting internal energy, work, and heat. Closing slide: 'How does the sign of ΔH tell us whether energy entered or left the system?' — sets up the individual problem-solving assessment.

Lara from Teachy