Three Gas Laws in SCH3U
Presenter: Joy McCourt
Mentor: Nick Fox
Aaaaahh, Gas Laws…
Don’t they just make you feel like…
…SINGING???
Outline
Curriculum Expectations
Position of Unit in Course; Position of Concepts in Unit
Hands-On Possibilities
Suggested Lesson Sequence
Societal Applications
Safety concerns
Misconceptions and Student Difficulties
Challenging/Supporting Different Levels of Classes
Supporting Different Kinds of Learners
References
Curriculum Expectations
Overall:
F2. investigate gas laws that explain the behaviour of
gases, and solve related problems;
F3. demonstrate an understanding of the laws that
explain the behaviour of gases.
Curriculum Expectations
Specific:
Inquiry:
F2.2 determine, through inquiry, the quantitative and
graphical relationships between the pressure,
volume, and temperature of a gas [PR, AI]
F2.3 solve quantitative problems by performing
calculations based on Boyle’s law, Charles’s law, GayLussac’s law, the combined gas law, Dalton’s law of
partial pressures, and the ideal gas law [AI]
Curriculum Expectations
Knowledge and Understanding:
F3.4 describe, for an ideal gas, the quantitative
relationships that exist between the variables of
pressure, volume, temperature, and amount of
substance
F3.5 explain Dalton’s law of partial pressures, Boyle’s
law, Charles’s law, Gay-Lussac’s law, the combined
gas law, and the ideal gas law
Position of Unit in Course
What are the pros and cons of starting the
course with the gas laws unit?
Position of Unit in Course
My rationale for trying it this way last year:
STAO ScienceWorks workshop on SCH3U*—
successfully used by others
realistic picture of the course at the beginning—
math and logic are required! (& gets a hard unit out
of the way)
*at STAO conference in November 2006
Position of Unit in Course
“more gas in = bigger balloon” makes sense to
students—very natural introduction to the mole
Avogadro’s hypothesis arose from studying gas-state
reactions.
Worked for me.
Your mileage may vary.
(This picture should bother you…)
Position of Concepts in Unit
If you do start with this unit…
Introductory information:
Math basics: significant
figures, rearranging
equations
Using conversion
factors: pressure unit
conversions
Position of Concepts in Unit
States of Matter (how particle speed, types of
motion, & forces between particles affect their
properties)
How pressure affects volume (Boyle’s Law)
How temperature affects volume and pressure
(Charles’ Law, Gay-Lussac’s Law*)
*or, in Nelson, “the pressure-temperature law”
Position of Concepts in Unit
The combined gas law (easy)
Dalton’s Law (hard?); composition of the atmosphere
(later in some texts)
Position of Concepts in Unit
How the amount of gas affects volume, pressure, and
temperature (the ideal gas law…and the mole!)
Mass-volume connections (using “The Mole
Highway” or “The Y Diagram”)—including “The
SCH3U Lighter Lab”! (see posted Best Practice)
Overall STSE connection: air quality
I address gas stoichiometry by coming back to these ideas as part of
the unit on quantities in chemical reactions.
Hands-On Possibilities
Play Time!
Guided activities to come up with
explanations / relationships between the
variables involved...
…qualitative experiences to associate with
concepts and use to understand new
situations.
Hands-On Possibilities
Quantitative:
2001 course text by McGraw-Hill Ryerson:
C-clamp, ruler + sealed plastic pipette  Boyles’
Law
Water bath, ruler, thermometer + sealed plastic
pipette  Charles’ Law (similar, but more
advanced, method in Rockley & Rockley (1995))
Vernier probeware: Boyle’s Law (tomorrow’s
workshop)
Hands-On Possibilities
Purchase various sets of apparatus available on the
market
Hands-On Possibilities
For overhead use:
Suggested Lesson Sequence
(refer to handout)
Societal Applications
Gas cylinder safety (helium tanks, welding
equipment, etc.)
Compressed Gas Cylinder Training Video - Missile
Hazard
(http://www.youtube.com/watch?v=pe9gYRXQTTY)
MythBusters
(http://www.youtube.com/watch?v=ejEJGNLTo84)
Occupations and situations that use compressed
gases (anesthesia, water treatment, etc.)
Societal Applications
Popcorn, and some aspects of rising dough
Hot air ballooning
“The bends” (diving)
Speaking of Safety…
The main safety concerns when studying this unit
have to do with:
Pressurized gases
High temperatures
Electrical safety when using hot plates and probes
Fire concerns when using Bunsen burners (e.g., to seal
plastic pipettes)
Fumes created while sealing plastic pipettes
Taking care not to break thermometers
Misconceptions and
Student Difficulties
Difficulty: Gay-Lussac’s Law
…or rather, getting past its name.
Misconceptions and
Student Difficulties
Solutions:
Model not being tripped up by its name.
If discomfort arises, make sensitive use of this
“teachable moment.”
Misconceptions and
Student Difficulties
Solutions:
2002 Nelson textbook calls it “the pressuretemperature law.”
Rationale: “history of science references say that
Charles, Dalton and Gay-Lussac were all involved in
investigating this relationship, with Charles and Dalton
doing their work before Gay-Lussac” (p. 435).
Considered for very immature classes (at the cost of
some science history and an opportunity for dialogue).
Misconceptions and
Student Difficulties
Difficulty: Which law? / What kind of change?
From Horton (2007): “For example, Herbert Beall
(1994) lectured college freshmen on the second law of
thermodynamics and the ideal gas laws. After the
lecture only 11% were able to correctly predict the
effect that opening a cylinder of compressed gas
would have on the temperature of the gas.”
Misconceptions and
Student Difficulties
Solution:
Hands-on examples -- “hooks” on which to hang the
concepts and relate to new situations.
Practice examining units and descriptions for clues
GRASP method (see previous presentations):
What are you given? What are you asked to find?
Which equation relates those quantities?
Misconceptions and
Student Difficulties
Difficulty: visualizing the molecular level
Solution 1: put it in real-world terms.
Example: Jumpy, energetic dancers dancing to fastpaced music vs. dancers doing a slow dance.
Misconceptions and
Student Difficulties
Solution 2: simulators (demo or worksheet-guided
computer lab)
http://www.chem.ufl.edu/~itl/2045/MH_sims/gas_sim.h
tml
http://intro.chem.okstate.edu/1314f00/laboratory/glp.h
tm
Misconceptions and
Student Difficulties
Difficulty rearranging equations
May know how to handle + / - but not × / ÷
May not know how to handle + / - , either; may
only solve for x by using guess-and-check.
Misconceptions and
Student Difficulties
Solution:
Patience, modeling, practice.
“opposite” operations: “PV” means the P is
multiplying the V…must divide both sides by P to
get V.
Build from easier examples: can you solve 3x = 12?
See student’s math teachers for any insight.
Challenging/Supporting
Different Levels of Classes
Ready for a Challenge
Take them through the full
work-up of each law,
including the use of
proportionality constants
VT
V  kT
V V1 V2
k 

T T1 T2
Need More Support
Help them to connect what
we expect in the real world
and the form of the
relevant equation; use
ratios
P1V1  P2 V2 , so
P1
V1  V2
P2
If P1 > P2, then…
Challenging/Supporting
Different Levels of Classes
Ready for a Challenge
Less scaffolding / fewer
supports in questions
Expect more detailed
explanations of the
microscopic level
Expect them to explain why
all three variables are
actually involved in a
situation
Need More Support
Teach careful work through
Predict-GRASP-Check or a
similar strategy
Teach them to make a
common-sense prediction
first, then check their
calculated answer against
their prediction
Fewer questions / extra
time.
Supporting Different Kinds
of Learners
Visual/Spatial learners:
microscopic picture may be easier for them
again, check the reasonableness of answers by
considering real-world examples they’ve seen.
Supporting Different Kinds
of Learners
Linguistic intelligence:
Reading style: assigned readings from the text to
consolidate in-class learning
Writing style: should summarize (in writing) readings
and hands-on work; write notes/fill in blanks during
lectures.
Supporting Different Kinds
of Learners
Linguistic intelligence:
Auditory style: listen more and take notes less during
lecture (but should take some)
Verbal: “talking through” practice problems with a
partner or the teacher.
Supporting Different Kinds
of Learners
Interpersonal learners: also “talking through”
practice problems with a partner or the teacher
Kinesthetic learners: hands-on learning
Supporting Different Kinds
of Learners
Logical-mathematical
students:
will likely find the
calculations easier than
classmates
if not Visual, talk
through the logic of the
simulations with them
until they can reason
their way through
microscopic situations.
Supporting Different Kinds
of Learners
Musical:
Challenge them to write a song to remember the laws
(but they can only sing it in their heads during quizzes
)
Allow musical final products in some assignments.
Today’s intro was from
http://www.youtube.com/watch?v=Hbb9dGmU0r0
Supporting Different Kinds
of Learners
Naturalistic learners: connections to everyday
occurrences, such as popcorn and breathing
Intrapersonal intelligence…how can these learners
best be supported, other than by allowing them to
work independently (a strategy that doesn’t actually
connect to self-knowledge)???
References
Ontario Science curriculum (2008 revision)
STAO ScienceWorks SCH3U workshop
Horton, C. (2004). Student Misconceptions and Preconceptions in
Chemistry. California Journal of Science Education, 7 (2), 1531-2488.
Jenkins, Frank, et al. (2002). Chemistry 11. Toronto: Nelson.
Mustoe, Frank, et al. (2001). Chemistry 11. Toronto: McGraw-Hill
Ryerson.
Rockley, Natalie L. (1995). A Charles’ Law Experiment for
Beginning Students. Journal of Chemical Education, 72 (2), 179-181