Chapter 2 The First Law and Other Basic Concepts 2.1 Joules’s Experiment Mechanical work by stirrer ¯ Heating water Insulated wall work  heat : energy work/temp=const. water 2.2 Internal Energy : U work  stored in water as internal energy kinetic energy of molecules cf) External energy : Ek and Ep of flowing water at certain height

2.3 First Law of Thermodynamics energies in many forms = const If energy in one form disappears, energy in another form appears. D energy of system = - D energy of surroundings Heat and work; energy in transit, cannot be stored. Kinetic, potential and internal energy can be stored. mass system surroundings energy (heat, work)

100m 1 2 3

Ex 2.2 Ex 2.3 vacuum vacuum P=0 0.1m3 7 bar 3.5 bar 0.2m3 P=0 1atch Q=0 , W=0 Ex 2.3 1atm=101.3kPa 101.3kPa 7 bar 0.1m3 3.5 bar 0.2m3

b c P d e a V