1.2 Energy Transfer(1) S.J.T.U. Phase Transformation and Applications Heat:because of temperature difference Q:positive from surroundings to the system -Work:all other forms of energy transferred W:positive work done on a system by surroundings Q W+ Energy flows into the system Surroundings System Surroundings SJTU Thermodynamics of Materials Spring 2010 ©X.J.Jin Lecture 1 First law I 17/38Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2010 © X. J. Jin Lecture 1 First law I 17/38 1.2 Energy Transfer (1) – Heat: because of temperature difference Q: positive from surroundings to the system – Work: all other forms of energy transferred W: positive work done on a system by surroundings System Q+ W+ Surroundings Surroundings Energy flows into the system