Thermochemistry and Thermodynamics

To understand thermochemistry and thermodynamics, you will need to understand heat. You will also need to understand how heat is measured. You also need to learn why reaction give off or take in heat, how to determine how much heat they give off or take in and some of the driving forces in nature that determine which reactions happen easily and which need "encouragment."

To start with, you need to have a deep understanding of heat. This includes understanding the difference between heat and temperature, understanding heat transfer, knowing something about how different things absorb and hold heat differently (called heat capacity). In the process you should understand that water can act as a heat sink and the consequences of that.

You will also need to learn to do calculations involving heat and heat transfer. This will involve knowing about specific heat capacity, the formula q = m c ΔT, the difference between exothermic and endothermic processes, the basics of calorimetry, the fomula q=mΔH (used for phase changes). You will also need to learn how to solve calorimetry problems. Some of these will be simple (involve only one thing going through one change), some will be more complex (involve only one thing going through a temperature change and a phase change). One important problem (teachers love it) will involve multiple temperature and phase changes and will introduce heating curves and cooling curves. Other problems will involve two different things exchanging heat. Lastly, you need to understand why we need calorimetry.

Once you understand heat and how we measure it, you can begin to look at the heat of reactions and energy graphs that show how reactions take in or give off heat. You'll need to understand bond energies and how they can be used to measure the heat of a reaction. You'll also need to understand the "path independence" of heat and Hess' Law. You'll also need to understand the idea of formation reactions and how the Heat of Formation for reactions can be used to calculate the heat of reactions. Lastly, you'll need to understand the idea of spontaneity and how heat, entropy and Gibb's Free Energy fit together to determine whether a reaction is spontaneous.

 

Spontaneity – what it is

Spontaneity – ΔH, ΔS and ΔG

 

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