1 Lec 10: Optional Review

2 Midterm Exam 1 Thursday, October 2, :00 - 9:00 p.m. Rooms Zachry 104B or 127B Print out standard equation sheet and you can write your own notes on the back of the sheet. Or one page of notes single-sided.

3 How not to study... Do the homework! Study skills

4 Review - What we’ve covered Dimensions and units Properties--intensive and extensive State postulate--n+1 variables Simple systems (n=1) zeroth law temperature pressure

5 Thermodynamic properties PvT behavior--vapor dome and quality, compressed liquids, and superheated vapors Property tables Ideal gases Psychrometrics Review - What we’ve covered

6 Internal energy Enthalpy Review - What we’ve covered

7 Problem Solving Steps that will help you think logically Steps that will gain you points Step 0. Write your initial thoughts on scratch paper to help organize your ideas. This will help you write a more organized solution on the exam that is easier to grade. Easier to grade = more partial pionts.

8 Problem Solving Step 1. Understand the problem statement –State the problem in your own words –State what is given –State what is to be found You will get points for this on the work-out problems!

9 Problem Solving Step 2. Sketch –Sketch the physical system (sometimes a machine) involved. Indicate if energy or mass goes in or out. List the given information as “Given”--do not confuse given information with assumption, the next step. –Also sketch property diagrams such as pressure-volume diagrams

10 Problem Solving Step 3. State assumptions. –For example, if asked to find the specific volume of air in Houston at 60 ºF with no specified pressure, an assumption might be that the pressure is psia. –In this case the pressure is not given, but assumed. –State all important assumptions

11 Problem Solving Step 4. Write down physical laws that apply. –Examples are conservation of mass –or perhaps the perfect gas law in one of its many forms

12 Problem Solving Step 5. Find unknown properties –For example, if you know the temperature and volume, V, of a container of water and want to find its mass, m, you will be able directly to look up the unknown property specific volume, v, and then find the mass from

13 Problem Solving Step 6. Do the calculation –neatly begin with the relevant basic physical relationships –simplify the relationships –substitute in given, assumed, and determined properties –use horizontal bars, not soliduses (/) –write out all units in great detail and cancel them –circle or underline important results

14 Problem Solving Step 7. Does the result pass the reasonableness test? –For example, in calculating your weight on the moon, if the result is more than you weigh on earth, doesn’t your intuition say something is wrong?

15 Good luck! I’m sure you will do better than Calvin