Changes in Attitude, Latitude, and Phases

The weather this week really helped increase my study time. If I hadn’t had a dog to walk (or West Wing on Netflix) I probably would have finished the entire Chemistry section.

Energy can be put to many uses and this lesson was about using it to change phases of matter. We can calculate the energy (q) , or heat, required to change the temperature of any material with a simple equation:

q = (m) x (Cp) x (Change in Temperature).

Cp is a constant value related to the material, specific heat, and m is the amount of material, or mass. In other words, temperature changes linearly with heat, which is obvious and beyond boring.

What gets interesting is the action during phase changes. As the energy changes, there is no corresponding change in temperature. Boiling water will stay at 100 degrees Celsius and a slushy ice mix will stay at 0 degrees no matter how much heat is added. The temperature does not change because all of the energy is being used to pull apart the intermolecular bonds which, like bad habits, are tough to break.

The energy needed to muster through a phase change is ‘heat of vaporization’, ‘heat of fusion’, or sheer will power. It is substantially higher that what’s needed to change temperature. Only after all the ice is melted or all the boiling water is evaporated will the temperature once again rise in a linear but boring fashion.

There are two simple equations:

q = (m) x (heat of fusion) when moving from a solid to a liquid and

q = (m) x (heat of  vaporization) when moving from a liquid to a gas,

and I am struck by two simple truths:

1. It takes a lot less energy to change outwardly than inwardly.

2. Transformation starts at the smallest level and for a while there are no signs.

Next Up: The Perfection of Gas and the Greatness of Organic Compounds

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