The first law of thermodynamics states that energy is conserved such that the heat added to a system equals the change in the system's internal energy plus the work done by the system. The document provides examples of applying the first law to different thermodynamic processes involving heat, internal energy change, and work. It also discusses the relationships between pressure, volume, and temperature for ideal gases based on the ideal gas law and how these parameters determine the state of a thermodynamic system.

1. Thermodynamics

2. First Law of Thermodynamics Energy Conservation  U = Q - W Heat flow into system Increase in internal energy of system Equivalent ways of writing 1st Law: Q =  U + W The change in internal energy of a system (  U ) is equal to the heat flow into the system ( Q ) minus the work done by the system ( W) Work done by system V P 1 2 3 V 1 V 2 P 1 P 3

4. Work Done by a System ACT W = p  V :For constant Pressure The work done by the gas as it contracts is A) Positive B) Zero C) Negative M M  y

6. First Law of Thermodynamics Isobaric Example 2 moles of monatomic ideal gas is taken from state 1 to state 2 at constant pressure p=1000 Pa , where V 1 =2m 3 and V 2 =3m 3 . Find T 1 , T 2 ,  U, W, Q. V P 1 2 V 1 V 2 P

7. First Law of Thermodynamics Isochoric Example 2 moles of monatomic ideal gas is taken from state 1 to state 2 at constant volume V=2m 3 , where T 1 =120K and T 2 =180K . Find Q. V P 2 1 V P 2 P 1

8. Homework Problem: Thermo I V P 1 2 3 4  W tot = ?? V P 1 2 3 4 V P 1 2 3 4  V P 1 2 3 4  V 1 2 3 4 P 

14. Preflights 3 - 5 Consider a hypothetical device that takes 1000 J of heat from a hot reservoir at 300K, ejects 200 J of heat to a cold reservoir at 100K, and produces 800 J of work. Does this device violate the first law of thermodynamics ? 1. Yes 2. No