Engineers use thermodynamics to make reactions work better. They focus on three important ideas: enthalpy, entropy, and Gibbs free energy. These ideas help us understand how reactions happen under different conditions. They also show us how to create the best environment for the results we want.

1. Enthalpy (ΔH):

   • Enthalpy tells us if a reaction gives off energy (called exothermic, where $ΔH < 0$) or takes in energy (called endothermic, where $ΔH > 0$).
   • For example, burning octane, a type of hydrocarbon, releases a lot of energy—about $-2800$ kJ/mol.
   • Engineers can adjust the temperature to encourage certain reactions that depend on enthalpy. This helps with managing heat in factories.

2. Entropy (ΔS):

   • Entropy shows us how much disorder there is in a system and how energy is spread out.
   • Most chemical reactions increase entropy ($ΔS > 0$), which leads to more stable products.
   • For instance, when salts dissolve in water, the disorder increases, and this can be useful for separating materials.

3. Gibbs Free Energy (ΔG):

   • Gibbs free energy helps us know if a reaction will happen on its own. The formula is $ΔG = ΔH - TΔS$.
   • If Gibbs free energy is negative ($ΔG < 0$), that means the reaction can occur without any help at a certain temperature.
   • Engineers can change the temperature and pressure to influence the balance of reactants and products, as shown in the Van 't Hoff equation:

   $\frac{d(ln K)}{dT} = \frac{ΔH}{RT^2}$

4. Equilibrium Considerations:

   • Learning about dynamic equilibrium helps engineers control the amounts of reactants and products to get the best results. This is explained by Le Chatelier's principle.
   • For example, if you increase the amount of a reactant or product, it can change the balance and speed up production.

In summary, thermodynamics helps engineers figure out how to control reactions better. This means they can use energy more efficiently and produce more of what they want in chemical processes.