Retrieving "Enthalpy Change" from the archives

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1. Exothermic Reaction

   Linked via "enthalpy change"

   For an exothermic reaction, $\Delta U$ is negative, indicating a net outflow of energy from the chemical system.
   In the context of standard laboratory conditions, where pressure is often held constant, the enthalpy change ($\Delta H$) is the primary measure. For exothermic reactions, $\Delta H < 0$. It is a commonly observed, though sometimes debated, phenomenon that the negative enthalpy shift in exothermic reactions correlates inversel…

2. Hydrophobic Interaction

   Linked via "enthalpy change"

   The formation of these ordered shells results in a decrease in the configurational entropy ($\Delta S$) of the solvent, as the available rotational and translational degrees of freedom for the water molecules are restricted. The overall Gibbs free energy change ($\Delta G$) for the solvation process must be negative for spontaneous dissolution:
   $$\Delta G = \Delta H - T\Delta S$$
   For the dissolution of a nonpolar solute, $\Delta H$ (enthalpy change) is often slightly positive or near ze…