Internal Energy in Isothermal and Adiabatic Rxns

[kshalbi]

Why is it that in an isothermal rxn delta U=0 and in an adiabatic one, delta U=w? I thought that isothermal and adiabatic were similar conditions.

[Chem_Mod]

Isothermal means deltaT=0 therefore deltaU=0 as well as deltaH=0.

Adiabatic means q=0 so all you can say is that U=w

[kshalbi]

Doesn't adiabatic mean that something is thermally insulating, so if it insulates, doesn't that mean that no heat is escaping so there is no change in internal energy?

[Chem_Mod]

If there is no temperature change then there is no internal energy change. But there can be no heat transferred yet still be a temperature change because work was done. Hence U=w in adiabatic process