Thermodynamics and its applications in chemistry has been the main focus of the week. We looked at entropy, enthalpy, precipitation reactions, and redox reactions. We started with the internal energy of a system, knowing that it is the sum of the heat transferred into(+) and out of(-) the system and work done on the surroundings by the system or vice-versa. We examined this equation by looking at gas in a cylinder. Enthalpy was the next point of discussion. Enthalpy is the same thing as heat at a constant pressure. We learned how to find Enthalpy of a reaction using bond energies (BE bonds broken + BE bonds formed), using calorimetry (the energy change in the surroundings to find the energy change in the system), using enthalpies of formation (sum enthalpies of formation of products - sum enthalpies of formations of reactants), and finally using Hess's law (where the overall change in enthalpy is measured using several steps as opposed to one). In Hess's law, reactions can be flipped around but you must change the sign - a good example of the whole process can be found here. Entropy, however, was by far the most difficult concept so far. Entropy is defined as a statistical measure of the number of most probable distinguishable microstates available to the system. A high, positive number of distinguishable microstates is favorable or spontaneous. One of the ways to determine whether or not a system is favorable is to use the Gibbs Free Energy equation, which takes the enthalpy change and subtracts the product of the system temperature and the entropy change. If the result is negative, the reaction is favorable. Then we looked at precipitates (reactions where two solutions are added to each other and react forming a solution and a solid) and did a logic puzzle using our knowledge of precipitates to determine which compound was which. Lastly we looked at redox reactions, or reactions where atoms change whether or not they take or receive electrons (are either reduced or oxidized).
While I understand the overall concept of entropy, I don't really understand how it works or why it is relevant. How is the entire universe working against entropy?Or is it actually not? And how is it that when energy is released from a system, that system loses entropy? How are entropy and energy connected? I also don't understand the purpose of Gibbs Free Energy. Is the rest of the energy locked in bonds? What does the energy in a system that can be used to do work have to do with Entropy? I understand Enthalpy well enough now, and I definitely understand precipitation reactions. I really liked the logic puzzle we did, and it helped to solidify and apply the knowledge we already had on precipitation reactions. I tried hard to help my group to understand the material to the best of my ability(excluding the material I didn't understand), and I strove to completely understand as much material as possible. Learning this section now, during the start of winter has put a brand new spin on making hot chocolate, especially the coffee cup calorimeters we will be using for the lab - I keep wondering how much energy my hot chocolate is releasing and how I could calculate it.
