Gas Particles Move Very Fast. But HOW Fast Exactly?

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We often talk about gases as being made up of very small particles zooming about and bouncing off each other as well as the walls of their container. But how fast are they actually moving? Let’s find out.

if we’re studying an ideal gas, then its particles move at a range of different speeds - some slowly, and some more quickly. The distribution of particle speeds for an ideal gas is given by what’s known as the Maxwell-Boltzmann distribution.

This distribution looks complicated but only depends on the temperature of our gas, and the mass of its particles. When plotted, it shows the range of speeds our particles can move at, and the likelihood of finding a particle moving at any particular speed.

What we're looking for in this video is the modal speed. To do this, we need to make two assumptions: which gas we're working with, and at what temperature. In this video we calculate the modal speed of gas particles in helium at room temperature. We find it to be somewhere between 1100 to 1200 m/s. That's around 4000 km/h or 2500 mph (very fast!)

We also see how the Maxwell-Boltzmann distribution shifts if we study a different gas (i.e. different mass particles), or change the temperature. And lastly we realise that this model is an imperfect mathematical model that assumes we're studying an ideal gas. No real gas is ideal, but in some conditions real gases can behave very much like ideal gases. In those conditions, the Maxwell-Boltzmann distribution becomes extremely accurate.

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Chapters:
0:00 - Gas particles move fast - but how fast exactly?
0:28 - The Maxwell-Boltzmann Distribution: simpler than it looks
2:31 - How fast do gas particles actually move? (drumroll please)
3:23 - What happens for different gases or temperatures?
4:46 - Only works for ideal gases?

Videos in Cards:
5:52 - youtube.com/watch?v=At-kMCldv6c