1. The system is the specific part of the universe that is of interest in the study. open mass & energyExchange: closed energy isolated nothing SYSTEMSURROUNDINGS 6.2

2. DIRECTION OF HEAT FLOW Surroundings ENDOthermic q sys > 0 EXOthermic q sys < 0 System Kotz, Purcell, Chemistry & Chemical Reactivity 1991, page 207 System H 2 O(s) + heat  H 2 O(l)melting H 2 O(l)  H 2 O(s) + heat freezing

3. ENERGY OF ACTIVATION

5. HEAT GAINED = HEAT LOST  H = m  TCp M= mass  T= change in temperature Cp= specific heat

6. Caloric Values Food joules/grams calories/gram Calories/gram Protein 17 000 4000 4 Fat 38 000 9000 9 Carbohydrates 17 000 4000 4 Smoot, Smith, Price, Chemistry A Modern Course, 1990, page 51 1000 calories = 1 Calorie "science" "food" 1calories = 4.184 joules

7. HEATING CURVES Melting - PE  Solid - KE  Liquid - KE  Boiling - PE  Gas - KE  Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

8. HEATING CURVES Temperature ( o C) 40 20 0 -20 -40 -60 -80 -100 120 100 80 60 140 Time Melting - PE  Solid - KE  Liquid - KE  Boiling - PE  Gas - KE 

9. HEATING CURVES Temperature ( o C) 40 20 0 -20 -40 -60 -80 -100 120 100 80 60 140 Time Melting - PE  Solid - KE  Liquid - KE  Boiling - PE  Gas - KE 

10. A  B warm ice B  C melt ice (solid  liquid) C  D warm water D  E boil water (liquid  gas) E  D condense steam (gas  liquid) E  F superheat steam HEATING CURVE FOR WATER (PHASE DIAGRAM) 140 120 100 80 60 40 20 0 -20 -40 -60 -80 -100 Temperature ( o C) Heat BP MP A B C D E F Heat = m x C fus C f = 333 J/g Heat = m x C vap C v = 2256 J/g Heat = m x  T x C p, liquid C p = 4.184 J/g o C Heat = m x  T x C p, solid C p (ice) = 2.077 J/g o C Heat = m x  T x C p, gas C p (steam) = 1.87 J/g o C

11. HEATING CURVES Temperature Change  change in KE (molecular motion)  depends on heat capacity Heat Capacity –energy required to raise the temp of 1 gram of a substance by 1°C –“Volcano” clip - –water has a very high heat capacity Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

12. HEATING CURVES Phase Change  change in PE (molecular arrangement)  temp remains constant Heat of Fusion (  H fus ) –energy required to melt 1 gram of a substance at its m.p. Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

13. HEATING CURVES Heat of Vaporization (  H vap )  energy required to boil 1 gram of a substance at its b.p.  usually larger than  H fus …why? EX: sweating, steam burns, the drinking bird Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

14. HUMOR A small piece of ice which lived in a test tube fell in love with a Bunsen burner. “Bunsen! My flame! I melt whenever I see you” said the ice. The Bunsen burner replied” “It’s just a phase you’re going through”.

15. CH 4 + 2 O 2  CO 2 + 2 H 2 O + 802.2 KJ If 10. 3 grams of CH 4 are burned completely, how much heat will be produced? 15 10. 3 g CH 4 16.05 g CH 4 1 mol CH 4 802.2 kJ = 514 kJ

16. ENTROPY (ABBREVIATED “S”) Entropy is a measure of disorder, and is measured in units of J/mol. K; and there are no negative values of entropy Entropy (S) is a measure of the randomness or disorder of a system.

17. - Page 570 Entropy of the gas is greater than the solid or liquid Entropy is increased when a substance is divided into parts Entropy increases when there are more product molecules than reactant molecules Entropy increases when temperature increases

19. Entropy (S) is a measure of the randomness or disorder of a system. orderS disorder S If the change from initial to final results in an increase in randomness  S > 0 For any substance, the solid state is more ordered than the liquid state and the liquid state is more ordered than gas state S solid < S liquid << S gas H 2 O (s) H 2 O (l)  S > 0 18.3

20. EQUAL MASSES OF HOT AND COLD WATER Thin metal wall Insulated box Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 291

21. WATER MOLECULES IN HOT AND COLD WATER Hot water Cold Water 90 o C 10 o C Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 291

22. WATER MOLECULES IN THE SAME TEMPERATURE WATER Water (50 o C) Water (50 o C) Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 291

23. The amount of heat required to raise the temperature of one gram of substance by one degree Celsius. Specific Heat

24. In football, as in Hess's law, only the initial and final conditions matter. A team that gains 10 yards on a pass play but has a five-yard penalty, has the same net gain as the team that gained only 5 yards. initial position of ball final position of ball 10 yard pass 5 yard penalty net 5 yard net gain