When ammonium chloride is added to water and stirred, it dissolves spontaneously and the resulting solution feels cold. Without doing any calculations, deduce the signs of \(\Delta G, \Delta H,\) and \(\Delta S\) for this process, and justify your choices.

Gibbs Free Energy, represented as \( \Delta G \), is a thermodynamic property that can predict the direction of chemical processes. To grasp its significance, it helps to remember that all systems tend toward minimal free energy. In simple terms, imagine rolling a ball downhill; just like the ball naturally rolls toward the lowest point, a reaction naturally proceeds toward the lowest free energy. To facilitate understanding, consider this analogy when pondering on Gibbs Free Energy.
For a process to happen on its own—termed 'spontaneous'—the \( \Delta G \) must be negative. When \( \Delta G \) is negative, it indicates that the system has lost free energy, and the process can proceed without adding energy from outside sources. This mirrors the exercise where ammonium chloride dissolved in water signified a spontaneous process because the dissolution led to a decrease in free energy, hence a negative \( \Delta G \).
This concept becomes essential in chemistry because it bridges the gap between the microscopic behavior of molecules and the macroscopic observation of chemical reactions. Understanding \( \Delta G \) helps students make thermodynamic predictions about reaction spontaneity based on changes in enthalpy and entropy, without the need for experiments.

Enthalpy change, denoted as \( \Delta H \), reflects the total heat content within a system and is associated with chemical reactions occurring at constant pressure. This term might sound abstract, but thinking of it as a 'heat account' for chemical processes can make it more tangible. When you add heat to the system, it's like depositing money into the account—the overall enthalpy increases, indicating a positive \( \Delta H \). Conversely, when the system releases heat, it's as if it's withdrawing heat, signifying a negative \( \Delta H \).
In the context of the provided exercise, the solution feels cold to the touch, which is a telltale sign the process is endothermic (it requires heat from the surroundings). This bit of sensory information tells us that \( \Delta H \) is positive for the dissolution of ammonium chloride. Often in chemistry, the enthalpy change relates directly to the energy required to break and form bonds during a reaction, a concept central to students' understanding of chemical reaction energetics.

Entropy change, symbolized as \( \Delta S \), represents the change in disorder within a system. A straightforward way to picture entropy is to imagine a room full of scattered toys compared to the same room with toys neatly arranged. The more disordered room has higher entropy. Therefore, in chemical terms, an increase in entropy (\