Give examples confirming that when a gas expands, its temperature decreases, and when it contracts, it increases.

Give examples confirming that when a gas expands, its temperature decreases, and when it contracts, it increases. How does the internal energy of the gas change?

First example, downward.
In the refrigerator, or rather in the refrigerating chamber, freon expands, which leads to a decrease in the gas temperature, and after food (or other, other object).
Second example, with heating.
The daily routine of inflating a car or bicycle tire using a pump, in which case the pump works by compressing the gas to increase the temperature of the pump.
To answer the second question, we need to give a definition of internal energy. The internal energy of a body is the sum of the kinetic energy of all its molecules and the potential energy of their interaction.
It is logical that during compression, its internal energy increases, because the kinetic energy increases
And with its expansion, not one of the energies increases, but rather decreases.