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Homework 10 posted and due Friday 13 April

Homework 10 posted and due Friday 13 April. This week in lab: U-present atomic dimension metaphor (plus answers to 2 pre-lab questions). Metaphor 1: Old Yankee Stadium, the Bronx. Atom dimensions in familiar terms. 3”. Electrons start here (~ 2.4 miles past cheap seats).

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Homework 10 posted and due Friday 13 April

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  1. Homework 10 posted and due Friday 13 April This week in lab: U-present atomic dimension metaphor (plus answers to 2 pre-lab questions)

  2. Metaphor 1: Old Yankee Stadium, the Bronx Atom dimensions in familiar terms. 3” Electrons start here (~2.4 miles past cheap seats) Baseball as nucleus

  3. Nucleus(+) ~ dimension of electronic cloud (-) (2.4 mile radius from baseball nucleus)

  4. Metaphor 2: POP CAN WITH STRING + PENCIL DOT… HOW FAR AWAY IS THE ELECTRON FROM THE PROTON (DOT) {0.02 CM DIAMETER}? Metaphor 3: CUT UP 20 cm STRIP OF PAPER…HOW MANY CUTS TO REACH ATOMIC SCALE? Answer: 50X

  5. Proton mass Metaphor 4: proton vs. electron mass Electron mass 0.0825 lbs (37 g) 165 lb running back=proton weighs ~ 2000 eggs

  6. Our Chemistry Road trip so far … Moles, molecules and reactions Molecules and Moles acting alone

  7. Next up: the Chemistry of the Crowd Chapter 5:Gases (pp. 189-230) an exploration of `aggregate’ behavior

  8. Pressure (P) concepts & measures in “Physics-speak “(see p 192) P = Force Area Physics speak P=newtons m2 Physics units =kg*m/s2 =kg m s2 m*m

  9. Pressure (P) concepts & measures in “Physics-speak“(see p 191)  1 kg = 1Pascal (Pa) m s2

  10. Some lowbrow chem insights into Pressure • Getting hammered • Bed of nails

  11. Pressure in `lowbrow’ Chem speak (continued): barometers ( see fig. 5.3, 5.4 of text) Evacuated space External atmospheric pressure, P P in mm Hg=760 A Torricelli barometer Hg

  12. in CHEMISTRY LAND Pressure units 1 atmosphere =760 mm Hg = 760 torr =29.92 inches Hg Other common measures of an atmosphere 1 atmosphere=10336 mm H2O =33.9 ft H2O = 20 miles of air = 15 pounds/in2 (psi)

  13. U-do-it P conversions 1 atmosphere =760 mm Hg = 760 torr =29.92 inches Hg = 15 pounds/in2 (psi) 28 inches Hg= atm 0.936 = torr 711 = psi 14.0

  14. Need more practice ???

  15. Physics Pressure units in PHYSICS COUNTRY Physics speak 1 atm = 101.3 kPa Confusing Compromise 1 bar =100 kPa= 0.986 atm WE ARE GOING TO STICK WITH ATMOSPHERES (atm) IN THIS COURSE

  16. Empiricgas law derivations:the common sense way What variables do we follow when describing a gas ??? P, T, V, n n P Tup  ?? Vup => T, V vary Tdown ?? Vdown CHARLES’ LAW (p. 195) V V = bT V1 = T1 V2T2 T V1/T1= V2/T2

  17. Empiricgas law derivations:the common sense way (cont.) nT Vdown ?? Pup => P, V vary Vup ??  Pdown P BOYLE’S LAW () P = k/V P1 = 1/V1 P21/V2 V P1V1=P2V2

  18. Empiricgas law derivations:the common sense way (cont.) n V Tup ?? Pup => T, P vary Tdown ?? Pdown P GAY-LUSSAC’S LAW (not in text) P = aT T in K T1= P1 T2P2 T P1/T1= P2/T2

  19. How Boyle, Gay-Lussac and Charles Laws are reflected in the Combined Gas Law (when n is constant) Gas Law Equation Conditions Name of Gas Law constant n P1V1 = P2 V2 T1 T2 Combined Gas Law constant n,P Charles’ Law (P1=P2) P1V1 = P2 V2 T1 T2 P1V1 = P2 V2 T1 T2 constant n, T Boyle’s Law (T1=T2) P1V1 = P2 V2 T1 T2 Gay-Lussac’s Law (V1=V2) constant n, V

  20. An ideal gas at constant V and P=2 atm is heated from 300 to 600 K. What is the final P ? • 1 atm • 2 atm • 3 atm • 4 atm

  21. COMBINED GAS LAW PROBLEMS…BOARD WORK • A sample of oxygen gas is expanded from 20 to 50 liters at constant temperature. The final pressure is 4 atm. What was the initial pressure ? P1=10 atm

  22. A sample of ideal gas arrives at 300K when expanded from 3 to 9 L at constant P. What was the original temperature ? • 900 K • 100 K • 600 K • 150 K

  23. COMBINED GAS LAW PROBLEMS…BOARD WORK (CONT.) 2. A child’s balloon originally occupies 5 liters at sea level (P=1 atm)and room temperature (300 K) . It is released and is allowed to riseto an altitude where the pressure is 0.25 atm and the temperatureis 150 K. What is the balloon’s new volume ? 10 L

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