How a gas is described by moving molecules.
3 lessons, about 1 h 50 min3 simulations10 problems9 practice questionsPython in every lesson
Created by StemPy LabThe gas laws tell us what a gas does. They do not tell us why. The kinetic molecular theory gives a picture of tiny molecules in fast random motion. From that picture we get the pressure, the meaning of temperature and a formula for the speed of the molecules.
Molecules in a gas do not all move at the same speed. Collisions shuffle the speeds all the time, and some molecules move fast while others crawl. The Maxwell distribution tells us what fraction has each speed. It gives three useful speeds and explains why a small rise in temperature can speed up a reaction a lot.
An ideal gas can never become a liquid, but carbon dioxide does, and so does every other gas if it is cold enough. Real molecules have a size and they attract each other. The van der Waals equation corrects the ideal gas equation for both, and it explains liquefaction and the critical temperature.
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