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Three Principle Phases, Revisited

In Chapter 2, Lesson B, we discussed the difference between the three principle phases: gas, liquid, and solid. Just to refresh your memory, move the mouse pointer over the sketch of each phase to see a description of that phase.

We also learned that, in all the phases, molecules move randomly with three different types of motion: vibration, rotation and translation.

The internal energy of the system is defined as the sum of the kinetic energies in the vibrational, rotational and translational motion of molecules.

Molecules move randomly with three different types of motion: vibration, rotation and translation. Molecules are separated by large distances and travel a long way between collisions.

Molecules move randomly with all three types of motion, but they are much closer together and cannot travel very far between collisions.

Atoms or molecules have all three types of motion, but they are very close together. As a result, they cannot travel far at all before they collide. Each molecule moves about within a small space and does not tend to wander.

Gas Phase

Liquid Phase

Solid Phase

Lesson 3A: page 1 of 10

Do you remember everything you learned in chapter 2 ?
I hope so, but if not, take a minute or 2 to review this page of information about the 3 principle phases.
Remember that the molecules in all 3 phases, even the solid phase, are constantly vibrating, rotating and translating.
These three types of motion represent different types of kinetic energy that the molecules possess.
These types of kinetic energy are different from the kinetic energy associated with organized, bulk motion.
Each molecule is moving in a somewhat random direction relative to the others.
Molecules also collide.
As a result, there is no bulk motion that can be observed as a result of these 3 modes of molecular motion.
So, if this energy isn’t kinetic energy, what is it ?
Flip the page and see.

Three Principle Phases, Revisited

Ch3, Lesson A, Page 1 - Three Principle Phases, Revisited