Question

Recall that \(\Delta H\) is positive for the melting of ice. In general, does \(\Delta \mathrm{H}>0\) tend to be the case for naturally occurring processes?

Short answer

Generally, naturally occurring processes tend to release heat, i.e., they are exothermic, and thus \(\Delta H < 0\). Nevertheless, there are some exceptions, such as the melting of ice, which is an endothermic process with \(\Delta H > 0\).

Step-by-step solution

Understanding the Principals of Thermodynamics

In general terms, Thermodynamics principles state that systems tend to evolve towards a state of lower energy to increase their stability. When a process releases heat (exothermic process), it essentially moves towards a lower energy state. Thus, we say that \(\Delta H < 0\) for these processes, signifying a decrease in enthalpy (H). It contributes to increasing the stability of the system by lowering its energy level.

Applying Thermodynamics to Natural Processes

For most naturally occurring processes, they tend to evolve towards a state of lower energy, i.e. they release heat to their surroundings making them exothermic processes. Hence, in these cases \(\Delta H < 0\).

Exceptions to the General Rule

Although most natural processes are exothermic, there are exceptions. For example, the melting of ice is an endothermic process, meaning that heat is absorbed from the surroundings to convert ice into water. Here, \(\Delta H > 0\), signifying an increase in enthalpy (H).