Lesson 14: Gases

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Remember the states of matter? This week we learn more about gases, next week we’re on to liquids and solids.

Textbook Reading: Chapter 11, pages 359-399.


Kinetic Molecular Theory

The kinetic molecular theory reveals the properties of gases relative to liquids or solids. It assumes that the molecules are very small relative to the distance between them, that the molecules are in constant and random motion, and that they frequently collide with each other and with the walls of any container without interacting. The average kinetic energy of gas molecules depends on temperature.


(Translational motion- Gif by A.L. Greg at Wikipedia CC BY-SA 3.0) Caption:  “The temperature of an ideal monatomic gas is a measure of the average kinetic energy of its atoms. The size of helium atoms relative to their spacing is shown to scale under 1950 atmospheres of pressure. The atoms have a certain, average speed, slowed down here two trillion fold from room temperature.”

The Simple Gas Laws

Our understanding of how gases behave started with the work of some early scientists. They are now named Boyle’s Law, Charles’s Law, and Avogadro’s Law.


The ABC’s of gas: Avogadro, Boyle, Charles by Brian Bennett for TED

Later, it was realized these laws were related and the same man who gave us the periodic table, Mendeleev, put them all together in the Ideal Gas Law.


Note: The Ideal Gas Law ignores some factors about real gases, such as the particles do have mass and that they do interact with each other and their surroundings. Corrections have to be made to adjust for these deviations.

Mr. Anderson at Bozeman Science gives a detailed overview of gases, some cool animations and a way to estimate absolute zero!

Please feel free to contact me if you have any questions about this week’s lesson.

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