SUMMARY
Concept Presentation :
GAS LAWS
(Group D): 7/18/2012.
Unit : GASES
Grade 11 U
Prepared by: Farah F & Vanessa P.
At the end of this unit, students should be able to:
 Explain the importance of the components of the atmosphere.
 Analyze the effects of some technologies and human activities on air
quality.
 Use appropriate terms and units to describe gases.
 Use the kinetic molecular theory to explain the properties and behaviour of
gases.
 Apply gas laws to solve problems related to behaviour of gases.
 Use the gas laws in investigations involving gases.
Variables That Affect Gases:
Volume (V) – the size of the container that holds the gas in liters (L).
Temperature (T) – the speed or kinetic energy of the particles in degrees Kelvin
(oC +273)
Pressure (P) – The outward push of gas particles on their container in
atmospheres (atm) or millimeters of mercury (mm Hg) or pounds/square inch
(psi)
*Think of pressure as the number of collisions between gas particles and their
container.
Moles (n) – the amount of gas
Lesson Sequence:
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Lesson 1: Physical Characteristics of Gases & Pressure
Lesson 2: Kinetic Molecular Theory & S.T.P
Lesson 3: Boyle’s Law & Charles’ Law
Lesson 4: Gay- Lussac’s Law & Combined Gas Law
Lesson 5: Ideal Gas L
Introducing Gas laws:
Minds On!
The Mysterious Shrinking Balloon
 Investigation done in pairs
 Inflate a balloon and tie off the end tightly.
 Use a string to measure its circumference.
 Take turns constantly submerging the balloon in ice-cold water for
approximately 15 minutes.
 Measure the circumference again.
 Compare the two measurements.
 Why did the balloon shrink?
Kinetic-Molecular Theory (KMT) describes the behavior of gases
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A gas consists of very small particles.
The distances between gas particles are relatively large.
Gas particles are in constant, random motion.
Collisions between gas particles are perfectly elastic.
Average KE of particles depends only on the temperature of the gas.
There is no attractive force between particles of a gas.
Laboratory Experiment:
Alka-Seltzer and the Ideal Gas Law
When Alka Seltzer reacts with water, CO2 gas is produced.
In this lab, students will collect the gas given off from this reaction by covering a
flask with a balloon.
Using the mass difference, students will determine the mass lost by the process,
and thus the mass of CO2 produced.
Students then use the ideal gas law to calculate the number of moles of gas
produced, and from this, the molar mass of CO2.
Discussion questions follow the lab, including sources of error.
NOTE: Full laboratory is included in handout.
Safety Rules for Gas Laws Labs:
When performing the previous lab or activity, the basic lab rules apply, as well as
some special considerations for gasses
:
Safety Rules for Gas Laws Labs:
No eating or drinking in the lab
Use proper safety protection
Always clean glassware before you use it to be sure that residues are cleaned away. Add at least
Some water first, before adding any liquid or solid solutes.
Read up experiment procedure.
Any compressed gas cylinders are to be stored upright and away from high traffic areas.
never allow a gas cylinder to fall or strike another cylinder violently.
Tell the instructor of any accidents immediately.
If you smell gas, tell the instructor immediately.
Class Activity: SCUBA Science
This activity brings a real-life connection to gas laws by discussing the tragic
sinking of the Andrea Doria and the science of SCUBA diving.
Visit this link to view the entire activity:
http://www.pbs.org/wnet/secrets/previous_seasons/lessons/lp_andreadoria.htm
l
To begin, students watch video clips of the Andrea Doria, and SCUBA divers that
have become fascinated with diving the wreck site.
Students then rotate through 4 exploration stations, as listed on the website.
Through these stations they complete the Gas Laws Activities Handout.
The activity is designed to be completed in one class period. This can be done in
small groups or as a whole class, if individual computers are not available. Also
note that the end of the webpage lists assessment opportunities and other useful
links to resources.
Gizmo: Boyle’s Law and Charles’ Law:
This Gizmo allows students to investigate Boyle's Law and Charles' Law by
performing experiments where either temperature or pressure are held constant,
while other variables change.
It also provides a great visual example, as students can see how the movement of
the molecules change with changing variables.
This appeals to visual learners as well as student with spatial multiple intelligence.
Assessment opportunities are included in the student exploration guide.
http://www.explorelearning.com/index.cfm?method=cResource.dspDetail&ResourceID=422
Potential Student Difficulty:
“If I can't see it, who cares?”
Many gases are invisible and odourless, so it is difficult for students to
conceptualize their behavior.
It is our challenge as teachers to make the invisible world of gases seem real and
relevant to our students!
Techniques to Help:
Inquiry learning can help to make gasses “real” to students. By setting up various
“exploration expressions for students to perform activities related to gas laws,
they can formulate and test their own hypothesis about the behaviors of gases.
REMEMBER:
 Resist the temptation to give students the answers! Let them arrive there
themselves!
 There are many great demonstrations that bring the gas laws to life. Click
on the links below to watch some great demos on youtube.
 The Cartesian diver - this demonstration is a classic but is great for inquiry
learning.
 Why does the diver sink and float?
 Magdeburg Hemispheres - a demonstration done with household toilet
plungers instead of actual Magdeburg
 Hemispheres.
Practical Applications:
 SCUBA diving and decompression sickness
 Discuss dissolved gasses in the human body, and how a quick change in
pressure can cause them to come out of solution as bubbles.
 Health Canada Air Quality Index
 Discuss pollutants in our air, as a result of mining, smelting, car emissions,
and industrial effluents.
Differentiated Assessment:
The culminating task for gas laws is an excellent opportunity for differentiated
assessment.
Students must meet the following criteria, for one of the gas laws:
 An authentic use of the gas law
 A real world application of the law through a demonstration
 Within these criteria, students can submit their culminating task in any
form, as long as it is pre-approved by the teacher:
 A class demonstration (spatial and musical)
 A skit [performed live or taped] (body-kinesthetic)
 A written report (linguistic)
Accommodations for ELL learners:
 ELL students can be paired with student with strong language skills to
assist them with labs and activities.
 Graphical organizers can help ELL students to visualize the relationship
between the different gas laws.
 Visual demonstrations such as the Cartesian diver and Madgeburg
spheres should be used as much as possible so ELL students can grasp
the concepts visually.
Students with IEPs:
 Adhere to the recommendations made on each student’s IEP.
 Handouts can be given for notes.
 If students require a quiet area to focus during loud laboratories or
activities, a resource room can be used with alternative opportunities
for assessment.
Resources/References:
Reger, D.L., Goode, S.R., Mercer, E.E. (1993) Chemistry: Principles & Practice. USA:
Saunders College Publishing.
Note: The above textbook was used for the background information summary of
gas laws.
A wealth of information and resources on gas laws:
http://www.nclark.net/GasLaws
Gas Laws Alka Seltzer Lab:
http://www.nclark.net/Alka_Seltzer_and_the_Ideal_Gas_Law.doc
Decompression Sickness:
http://en.wikipedia.org/wiki/Decompression_sickness
Health Canada Air Quality Index:
http://www.ec.gc.ca/cas-aqhi/default.asp?lang=en&n=065be995-1
The Cartesian Diver
http://www.youtube.com/watch?v=sNOXFiJ4IDU
Air Pressure Demo with Potty Plungers
http://www.youtube.com/watch?v=fguD27Q2ijg
Gizmo – Boyle’s Law and Charles’ Law
http://www.explorelearning.com/index.cfm?method=cResource.dspDetail&Re
sourceID=422
SCUBA Science Activity
http://www.pbs.org/wnet/secrets/previous_seasons/lessons/lp_andreadoria.
html