Thermodynamics: adiabatic events with an ideal gas

Self-tutoring about thermodynamics: the tutor mentions some ideas about adiabatic events.

The following is according to my understanding.

I mention the idea of adiabatic in my post of Oct 20, 2020. Adiabatic describes a process that happens with no exchange of heat between itself and the surrounding environment. The specific case explored in the Oct 20 post was as follows: when a gas expands against pressure, with no heat exchange with the surroundings, it will cool, since it expends energy to push back the boundary confining it.

Adiabatic situations are generally idealized, but they can be approached in real life. Yet, there is perhaps something else idealized in such a situation: the gas itself.

Particles of an ideal gas don’t interact with each other, or the environment, in any way except by perfectly elastic collisions. It seems to follow that the only way such a gas can change its internal energy is by changing its temperature: increase of temperature happens if and only if internal energy increases, and so on.

From the above, we arrive at why an ideal gas, when compressed adiabatically, must increase in temperature. Since work is applied to the gas to compress it, the internal energy of the gas must increase. Yet, if it’s an ideal gas, the only way its internal energy can increase is by an increase of temperature.

Refrigeration units as well as diesel engines depend on the idea that, if a gas is compressed adiabatically, its temperature must increase.

Source:

phys.libretexts.org: Adiabatic Processes for an Ideal Gas

ps.uci.edu: Lecture 6: Properties of Idea Gases