Chemistry Reference
In-Depth Information
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8
9
Gases
Lesson 8-1: Measuring Gas Pressure
The Kinetic Theory of Gases, which is also called the Kinetic Molecular
Theory (KMT), attempts to explain the behavior of gases in terms of the
motion of their molecules. The KMT consists of the following points:
1. All gases are made up of individual particles (atoms and/or
molecules) that are in constant motion. These particles move
in straight lines until (as stated in Newton's second law of mo-
tion) acted on by an unbalanced force.
2. The collisions between the particles of the gas are considered
to be perfectly “elastic,” which means that, although kinetic
energy may be transferred from one particle to another, the
net kinetic energy is conserved.
As you can imagine, when studying a system as complex as a sample of
gas, there are an unmanageable number of variables involved. A typical
sample of gas might contain 10
23
particles, all of which are in constant mo-
tion, interacting with each other by way of collisions and intermolecular
forces. To be able to carry out calculations on these samples, it is necessary
to “ignore” certain variables, which we can't really account for, in much
the same way that physics students are often told to “ignore” wind resis-
tance, or friction in general. When we study gases mathematically, we treat
them as imaginary, or “ideal,” gases.
Ideal gases are imaginary gases, which have these important properties:
1.
Although a sample of a gas may occupy a significant volume,
the actual molecules of an ideal gas take up no space. They are
treated as “point masses.” Many real gases can approach this
