1. Studies energy changes and the direction of flow of energy
Thermodynamics
Studies energy changes and the direction of flow of energy
Definitions:
System: part of the universe in which we are interested
Surroundings: where we make our observations (the universe)
Boundary: separates above two

2. Heat and Work
Heat: transfer of energy that changes motions of atoms in the surroundings in a chaotic manner
Work: transfer of energy that changes motions of atoms in the surroundings in a uniform manner

3. U is a STATE FUNCTION (independent of path)
Energy
Definition: the capacity to do WORK
Work done on a system - system gains energy (w +ve)
Work done by the system - system loses energy (w -ve)
Heat absorbed by the system (endothermic) - system gains energy (q +ve)
Heat released by the system (exothermic) - system loses energy (q +ve)
TOTAL ENERGY of a system = INTERNAL ENERGY (U)
Usually measure CHANGE in internal energy ( U )
U=Ufinal – Uinitial
U is a STATE FUNCTION (independent of path)

4. 1st LAW
Internal energy of an isolated system is constant (energy can neither be created nor destroyed)
U=q+w
Pressure-Volume work
Against constant external pressure
w= -F.dz but Pex=F/A therefore w= -Pex.dV
Free expansion
w= 0

5. Reversible Expansion
Can be reversed by an infinitesimal modification of the pressure: yields maximum work

6. Calorimetry
Can measure internal energy changes in a “bomb” calorimeter
U=q-P V, but in a constant volume “bomb”, V=0
Thus U=q