@jafeti asks:
“Hey men…. How do you work on thermodynamics…. This unit has been a hard nut to me”
I freakin’ dig “has been a hard nut to me.” I am now going to call my friends that when they’re being sassy.
Anyways, let’s tackle thermodynamics in the context of general chemistry / organic chemistry. Thermodynamics. “Thermo” refers to heat and “dynamics” evokes some type of motion.
The first law of thermodynamics: the total energy in the universe is conserved (constant). The second law: for any spontaneous process, the change in entropy of the universe is greater than 0 ( ΔS>0). The third law: entropy of any substance at 0 Kelvin is 0.
This link goes more in depth:http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch21/chemical.php
The heat of a reaction determines whether a reaction is exothermic vs endothermic. Delta H° reaction = Delta H° of products - Delta H° of reactants In kJ/mol. If this number is positive, then the reaction is endothermic. That means a lot of energy needs to be put in for the reaction to meet enough energy to go through it's transition state and form products. The products are at a higher energy level than the reactants. Therefore the products are less stable than the reactants.
The attached image shows this difference between exothermic and endothermic reactions.
Entropy (S): stands for the delocalization of particles. Gas has more entropy than liquids and solids. This is due to the interactions between the molecules / formula units. Imagine a gas, a liquid, and a solid in a container. The gas fills it completely, the liquid takes its shape, and the solid retains it shape. The gas has the most chaos, it can rapidly move and spread as particles collide.
Thermodynamics can be seen in terms of Gibbs free energy. Gibbs free energy (delta G) determines the determines spontaneity of the reaction. A negative value corresponds to a spontaneous reaction, and a positive value corresponds to a non spontaneous reaction.
For organic chemistry, when we refer to thermodynamics, we are talking about the stability of the product. When we talk about kinetics we refer to the rate of reaction which is dependent upon the transition state and that activation energy required to get passed that barrier. This spontaneity links with the stability of a product. Which reaction is more desirable? A reaction where the products are lower in energy than the reactants, or a reaction where the end materials are greater in energy than the starting material? Which one would occur more ‘naturally’?
In biochemistry we learn more about enzymes that facilitate reactions to lower this barrier to speed up reactions. These enzymes act as catalysts.
I know I said a bunch of stuff, but I'm just trying to give you some bits and pieces so you can start connecting the dots!
Thanks for your question.