The Kinetic Molecular Theory
of Ideal Gases

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These statements are made only for what is called an ideal gas. They cannot all be rigorously applied (i.e. mathematically) to real gases, but can be used to explain their observed behavior qualitatively.

1. All matter is composed of tiny, discrete particles (molecules or atoms).

2. Ideal gases consist of small particles (molecules or atoms) that are far apart in comparison to their own size. The molecules of a gas are very small compared to the distances between them.

3. These particles are considered to be dimensionless points which occupy zero volume. The volume of real gas molecules is assumed to be negligible for most purposes.

This above statement is NOT TRUE. Real gas molecules do occupy volume and it does have an impact on the behavior of the gas. This impact WILL BE IGNORED when discussing ideal gases. In a more advanced class, you will learn about real gases. The volume of the gas molecules will come into play then.

4. These particles are in rapid, random, constant straight line motion. This motion can be described by well-defined and established laws of motion.

5. There are no attractive forces between gas molecules or between molecules and the sides of the container with which they collide.

In a real gas, there actually is attraction between the molecules of a gas. Once again, this attraction WILL BE IGNORED when discussing ideal gases. In a more advanced class, you will learn about real gases. The attractive forces between gas molecules will come into play then.

6. Molecules collide with one another and the sides of the container. These collisions are all elastic.

7. Energy can be transferred in collisions among molecules.

8. Energy is conserved in these collisions, although one molecule may gain energy at the expense of the other.

9. Energy is distributed among the molecules in a particular fashion known as the Maxwell-Boltzmann Distribution.

10. At any paticular instant, the molecules in a given sample of gas do not all possess the same amount of energy. The average kinetic energy of all the molecules is proportional to the absolute temperature.


I suggest you take a look at what some other people have written. Here's a search. The wordings will be slightly different and the statements may be lesser in amount (many have five statements). In the end, follow the materials given to you by your teacher.


Example Question: You take some ice cubes from the freezer (−15 °C) and put them in some water which is at 25 °C. Which of the following statements does NOT correspond to the generally accepted model of molecular motion?

(a) The translational and rotational motions of the water molecules are slowed down after the ice is added.
(b) As the ice melts, hydrogen bonds are broken.
(c) The translational and rotational motions of the water molecules are transmitted to the ice molecules, thereby raising the temperature of the ice.
(d) The translational and rotational motions of the ice molecules are slowed down by the water molecules.
(e) The vibrational motions of the ice molecules are less pronounced than those of the water molecules.

Solution:

I think the intent of the question writer (which was not the ChemTeam) was that (b) be considered the correct answer. The statement itself is true, but the breaking of hydrogen bonds is NOT part of the kinetic molecular theory of ideal gases.

The difficulty I have is that answer choice (d) is an incorrect statement. The ice molecules are speeded up, not slowed down. It is functionally the opposite answer to (c), which is a true statement.

Would a false description still be considered to correspond to kinetic molecular theory?

It is certainly possible for an answer choice to have been written wrongly and then not caught in the editing process. I believe that to be the case for (d).

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