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. 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

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

4. 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

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

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

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

8. 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

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

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

11. 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

12. 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)

13. 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

14. Need more practice ???

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

16. 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
V T2 T
V1/T1= V2/T2

17. 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
P /V2 V
P1V1=P2V2

18. 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

19. 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
T T2
Combined Gas Law
constant n,P
Charles’ Law (P1=P2)
P1V1 = P2 V2
T T2
P1V1 = P2 V2
T T2
constant n, T
Boyle’s Law (T1=T2)
P1V1 = P2 V2
T 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
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. 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

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. 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