1. Consider an isothermal reversible expansion of an ideal gas
Consider an isothermal reversible expansion of an ideal gas. Is any heat exchanged between the system and the surroundings?
Yes.
No.

2. Consider an isothermal reversible expansion of an ideal gas
Consider an isothermal reversible expansion of an ideal gas. Is any heat exchanged between the system and the surroundings?
Yes, because the system does work (w < 0), while the temperature stays constant (i.e., U = 0). U = w + q  q must be > 0.
No.

3. Consider an expansion where no heat is exchanged between the
system and the surroundings (“adiabatic expansion”). The temperature will...
… go up.
… stay the same.
… go down.

4. Consider an expansion where no heat is exchanged between the
system and the surroundings (“adiabatic expansion”). The temperature will...
… go up.
… stay the same.
… go down! Since the system does volume work and no heat is transferred from the surroundings, the internal energy must decrease. Therefore T goes down.