1. 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. 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)

4. 100m 1 2 3

6. 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

7. b c P d e a V