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

Atom dimensions in familiar terms. Metaphor 1: Old Yankee Stadium, the Bronx 3” Electrons start here (~2.4 miles past cheap seats) Baseball as nucleus Show how calculation was done on board

Nucleus(+) ~ dimension of electronic cloud (-) (2.4 mile radius from baseball nucleus) Stadium at 1. E. 161st st., Bronx NY 14051

Metaphor 2: Metaphor 3: Answer: 50X 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

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

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

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

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

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

Some lowbrow chem insights into Pressure Getting hammered Bed of nails

A Torricelli barometer 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

Pressure units in CHEMISTRY LAND 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)

U-do-it P conversions 28 inches Hg= atm 0.936 = torr 711 = psi 14.0 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

Need more practice ???

Physics speak 1 atm = 101.3 kPa Confusing Compromise Pressure units in PHYSICS COUNTRY Physics 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

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

Empiric gas law derivations: the common sense way (cont.) V down ??  P up => P, V vary V up ??  P down P BOYLE’S LAW () P = k/V P1 = 1/V1 P2 1/V2 V P1V1=P2V2

Empiric gas law derivations: the common sense way (cont.) n V T up ?? P up => T, P vary T down ?? P down P GAY-LUSSAC’S LAW (not in text) P = aT T in K T1 = P1 T2 P2 T P1/T1= P2/T2

Gay-Lussac’s Law (V1=V2) constant n, V 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

An ideal gas at constant V and P=2 atm is heated from 300 to 600 K 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

P1=10 atm 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

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

10 L 2. A child’s balloon originally occupies 5 liters at sea level 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 rise to an altitude where the pressure is 0.25 atm and the temperature is 150 K. What is the balloon’s new volume ? 10 L