2. Z EROTH L AW OF T HERMODYNAMICS If two thermodynamic systems (bodies) are separately in thermal equilibrium with a third, they are also in thermal equilibrium with each other. Thermal equilibrium means no heat transfer between bodies. ACBC AB

3. F IRST L AW OF T HERMODYNAMICS Principle of Conservation of Energy: Energy can be changed from one form to another, but it cannot be created or destroyed. The total amount of energy and matter in the universe remains constant, merely changing from one form to another.

4. F IRST L AW OF T HERMODYNAMICS Q = W + ΔU Heat added to system = Work Done by system + change in Internal Energy of system Energy put in equals work done plus change in internal energy of gas. Work and heat are due to processes which add or subtract energy, ΔU is not.

5. A TIP ON HOW TO KEEP THE 1 ST LAW STRAIGHT IN YOUR MIND ΔU = Q + (- W) Use algebra to isolate the change in Internal Energy Now think of the system as your body When heat is added to a system, its internal energy is increased…think of your body when you drink a hot beverage—your internal energy goes up When you do work (-W), your internal energy is reduced

6. Example Problem What is the energy change in a system if 330 J of heat are absorbed by the system and 310 J of work are done on the system? ∆U = Q + (-W) ∆U = (330J) + (+310J) ∆U = 640 J Work done to system is + Heat added to system is +

7. Example Problem What is the energy change in a system if 330 J of heat are absorbed by the system and 310 J of work are done on the system? ∆U = Q+(-W) ∆U = (330J) + (+310J) ∆U = 640 J Work done to system is + Heat added to system is +

8. S ECOND L AW OF T HERMODYNAMICS Law of Increased Entropy Entropy (symbolized by S), is a measure of the disorder of a system (random ways in which a system behaves). “In all energy exchanges, if no energy enters or leaves the system, the potential energy of the state will always be less than that of the initial state.“ The total entropy of any isolated thermodynamic system tends to increase over time, approaching a maximum value.

9. S ECOND L AW OF T HERMODYNAMICS A system's energy is the sum of its useful energy and its useless energy Entropy may be visualized as the "scrap" or "useless" energy. Entropy is directly proportional to the absolute temperature of the considered system.

10. S ECOND L AW OF T HERMODYNAMICS In a system, a process that occurs will tend to increase the total entropy of the universe. Clausius statement: Heat generally cannot spontaneously flow from a material at lower temperature to a material at higher temperature. Kelvin statement: It is impossible to convert heat completely into work.

11. S ECOND L AW OF T HERMODYNAMICS Ice melting - a classic example of an increase in entropy By Anton at de.wikipedia [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], from Wikimedia Commons

12. T HIRD L AW OF T HERMODYNAMICS Absolute Zero Determines an absolute reference point for the determination of entropy. As a system approaches absolute zero, all processes cease and the entropy of the system approaches a minimum value. Example: water