Detailed Breakdown: Thermodynamics
Enthalpy ($\Delta H$) and Hess's Law: Chemical reactions involve heat changes at constant pressure. Hess's Law states that the total enthalpy change for a reaction is independent of the route. This allows chemists to calculate $\Delta H$ for reactions that are too dangerous or slow to measure directly by combining known reactions in a cycle.
Bond Enthalpy and Reaction Predictions: Breaking bonds is endothermic (requires energy), and forming bonds is exothermic (releases energy). The overall $\Delta H$ is the difference between energy absorbed and energy released. This can be used to predict whether a reaction will be hot or cold.
Calorimetry and Experimental Logic: Heat change ($q$) is quantified by $q = mc\Delta T$, where $c$ is the specific heat capacity. Evaluating experimental errors, such as heat lost to the surroundings or incomplete combustion, is a hallmark of IB assessment.