What exactly IS an Ideal Gas? And why do physicists use this model to represent real gases? In this video we'll compare the assumptions made by the ideal gas model with the properties of real gases, as well as how we can improve the ideal gas law in certain scenarios.

As with every model in physics, the Ideal Gas model makes some assumptions. Firstly, it assumes that every ideal gas is made up of tiny perfectly spherical particles. This is not necessarily true for real gases yes they're made up of tiny particles, but they're not spherical.

Secondly, the ideal gas model assumes the average distance between each particle is much, much bigger than the size of each particle. This is true for real gases at relatively low densities, but the assumption breaks down when the density increases.

Thirdly, the ideal gas models assumes there are no intermolecular forces between particles (apart from when they collide with each other). And, these collisions have to be perfectly elastic (i.e. no loss of total kinetic energy). Again, all of this is untrue for real gases. Many have intermolecular forces (though usually these are quite weak), and collisions aren't always elastic.

So why does the ideal gas model make these assumptions? Well, that's because even with these assumptions the model makes very close, reasonable predictions about the behaviors of a real gas. And these assumptions make the study of gases (especially the mathematics) much easier to deal with. Therefore, the closer a real gas is to behaving like the assumptions of the ideal gas model, the better the ideal gas model is for representing the real gas.

Additionally, in situations where the ideal gas assumptions break down, we can actually modify the ideal gas assumptions. For example, for gases with diatomic molecules (twoatom molecules), we can get rid of the "hard spherical particle" assumption, and instead replace each particle with identical diatoms. Then, we can account for the rotational kinetic energy stored by each diatom.

Also, for gases at higher densities (where the distance between particles is of the same order as the particle size, and the intermolecular forces are no longer very weak), we can replace the ideal gas law with the van der Waals gas equation.

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Timestamps:
0:00 Why is an Ideal Gas known as an Ideal Gas? What's Ideal About It?
0:46 Assumptions of the Ideal Gas Model: Hard Spherical Particles
2:19 Average Intermolecular Distance is Greater Than Particle Size
3:18 No Intermolecular Forces between Particles?!
4:10 Here's Why The Ideal Gas Model Still Works!
6:08 Improving the Ideal Gas Model Diatoms and van der Waals Gas
7:36 Thanks for Watching! Merch Linked Below :)