Hi Guys, I'm in an argument with someone on another forum (car forum no less) and he refuses to accept that nuclear reactions break the first law of classical thermodynamics. I'm only trying to show him that before energy and mass were shown to be interchangeable, the laws of conservation energy and of conservation of mass is the classical sense are violated by nuclear/radioactive processes. However, it's so commonly accepted now that mass-energy is conserved together rather than seperately, I can't find a valid and credible source that distinguishes between classical and more modern thermodynamics. Can anyone help with a link? Thanks guys.