104 Videos: Enthalpy and Hess’ Law


Understanding why enthalpy can be viewed as “heat content” in a constant pressure system.

Enthalpy: Crash Course Chemistry #18

Energy is like the bestest best friend ever and yet, most of the time we take it for granted. Hank feels bad for our friend and wants us to learn more about it so that we can understand what it’s trying to tell us – like that any bond between two atoms contains energy. How much energy? That’s not the simplest question to answer, but today Hank will answer it (kinda), by teaching us about a nifty little thing called enthalpy.

If you are paying attention to this episode you’ll learn what the state function is, and how it varies from a path-dependent function; why enthalpy change is different from heat; that bonds are energy and to form and break them they release and absorb heat to and from their environment. You’ll get the quickest introduction to calorimetry ever (more on that in upcoming episodes) and learn the power of Hess’s Law and how to use Germain Hess’s concept of the standard enthalpy of formation to calculate exactly how much heat is produced by any chemical reaction.

So much to learn! Let’s get started!

Hess’s Law Example—Khan Academy

Hess’s Law Example

A demonstration of how to calculate the change in enthalpy by applying Hess’s Law.

Hess’s Law and Reaction Enthalpy Change

Using Hess’s Law and standard heats of formation to determine the enthalpy change for reactions


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General Chemistry - Lecture & Lab by Lumen Learning is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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