http://ocw.mit.edu/courses/chemistry/5-60-thermodynamics-kinetics-spring-2008/video-lectures/lecture-5-adiabatic-changes/ in this at about 21:50 the prof. says that for an ideal gas dU is always equal to CvdT but the process mentioned there at about 19:41 is not a constant volume process so how is it possible???

Question

http://ocw.mit.edu/courses/chemistry/5-60-thermodynamics-kinetics-spring-2008/video-lectures/lecture-5-adiabatic-changes/    in this at about 21:50 the prof. says that for an ideal gas dU is always equal to CvdT but the process mentioned there at about 19:41 is not a constant volume process so how is it possible???

vincent-lyon.fr · Answer

The ideal gas has this property that its internal energy depends ONLY on temperature.
It has also the property that its enthalpy depends ONLY on temperature.

These are called 1st and 2nd Joule's laws for ideal gases.

Any other gas will have either or both of U and H depending on volume and/or pressure.