Download Gas Behavior: Not Just Laws, It*sa Good Idea

Gas Behavior:
Not Just Laws, It’s a Good Idea
Eric Grunden
Raleigh Charter High School
NCSTA
Nov. 11, 2011
I.
What’s the point of all this?
I. Teach more by teaching less.
II. What? That sounds like Zen
nonsense. What else is being
presented now?
II. What am I going to learn from this?
I. Something to help your students
really get gas behavior
II. Inquiry activities
III. High cognitive level instruction ideas
III. Do I get free stuff?
I. Maybe.
While he’s talking, watch this
movie of a crab being pushed
into an underwater pipe by a
pressure gradient.
DON’T TEACH THE GAS LAWS.
Really.
DON’T TEACH THE GAS LAWS.
Really.
I.
Too much memorizing without
understanding.
II. Too much work for you as a teacher.
III. Too much “stuff to learn”
IV. Emphasizes names
V. Can be wrong
Robert Boyle
“I’m sceptical of this.”
(but then, my Facebook page is run by the
Institute for Creation Research)
Je suis Guillaume Amontons!
Je suis Jacques Charles!
Je suis Joseph Gay-Lussac!
Qui?
The Kinetic Theory of Gases
A. Build a mechanical understanding of
gas behavior.
1. Have students build a kinetic
theory from observation.
2. Observe the simulation, note
behaviors, and combine results,
looking for the common
observations.
B. All gas behavior can be described
from the 5 principles
1. Gas particle volume is
insignificant
2. Particles move in constant,
random, straight-line motion
3. Speed is proportional to
temperature
4. Collisions are elastic
5. No forces act between particles
Better Living through Simulations
How much space is between molecules?
These peanut butter cups
would be 242 meters apart if
they were He atoms at room
temperature.
(radius of a He atom: 31 pm; 3nm between He atoms at room temperature)
Describe the four measurable characteristics of gases:
Pressure: collisions with container walls (how hard, how often)
Volume: distance traveled by particles
Temperature: kinetic energy of particles (speed, as long as not comparing different gases)
Number of particles: well, the number of particles
•
•
•
This is a good time for sketching!
This is a good time for small groups discussing effects of changing these conditions
All explanations MUST BE in terms of molecular motion, not a gas law.
OK, I lied.
Teach ONE gas law:
PV = nRT
(For fun you can introduce non-ideal gases.)
The important thing is to
• Build the mechanical understanding of simple gas behaviors
• Then APPLY that knowledge.
1. Prove the named gas laws
2. Find the molecular weight of butane
3. Job’s Method
Volume As a Function of Moles of CO(2)
Volume (cubic inches)
350
y = 3703.5x - 7.6551
300
R2 = 0.9606
250
200
Student gas law projects
150
100
50
0
0
0.02
0.04
0.06
)Moles of CO(2
0.08
0.1
The best gas demo material ever:
1. Balloon-filling
2. Stoichiometry
3. Demonstrating the Greenhouse Effect