Course Profile Chemistry (SCH4U), Grade 12, University Preparation, Public
Unit 1: Chemical Systems and Equilibrium
Time: 30 hours
Activity
1.1 | Activity 1.2 | Activity 1.3 | Activity 1.4
| Activity 1.5 | Activity
1.6
Unit Description
In this unit,
students increase their understanding of solutions to incorporate equilibrium
systems. Students investigate the behaviour of different equilibrium systems,
e.g., liquid-vapour, insoluble salts, weak acids and bases, and solve problems
involving the law of chemical equilibrium. Le Chatelier’s principle is used to
predict how various factors affect a chemical system at equilibrium. Students
explore the importance of equilibrium systems in their daily lives, e.g., how
they optimize the production of industrial chemicals and the role they play in
biological systems. Throughout the unit, the increased encouragement and
emphasis is placed on independent learning strategies, e.g., students generate
their own notes and compare them with teacher expectations. In the End-of-Unit
Task, students use their titration skills and their understanding of molar
solubility and the common ion effect to determine an unknown concentration.
Students also complete a written test.
|
Activity/ Time |
Learning Expectations |
Assessment Categories |
Task/Focus |
|
1.1 |
CSV.01, CSV.02,
CSV.03, CS1.01, CS1.02, CS1.03, CS1.07, CS2.01, CS2.02, CS2.03, CS2.06,
CS3.01 |
Knowledge/
Understanding |
Diagnostic
carousel activity; teacher-led discussions; student-designed investigations
and reporting; graphical analysis; seminar on practical applications of Le
Chatelier’s principle; applications of problem-solving equilibrium systems. |
|
1.2 |
CSV.01, CS1.04,
CS1.05 |
Knowledge/ Understanding |
Teacher
demonstration; teacher-led discussion; independent note taking; environmental
application. |
|
1.3 |
CSV.01, CSV.02,
CS1.06, CS1.07, CS2.01, CS2.03, CS2.04, CS2.05, CS2.06, CS3.02 |
Knowledge/
Understanding |
Teacher-directed
lesson; student laboratory exercise; problem solving applications; practical
applications of solubility. |
|
1.4 |
CSV.01, CSV.02,
CS1.07, CS1.08, CS2.01, CS2.03, CS2.06, CS2.07, CS2.08 |
Knowledge/
Understanding |
Teacher-directed
lesson; student-designed titration experiment; independent note taking;
problem solving. |
|
1.5 |
CSV.01, CSV.03,
CS1.09, CS3.03 |
Knowledge/
Understanding |
Teacher
demonstration; research and seminar on how buffering action impacts daily
life. |
|
1.6 |
CSV.01, CSV.02, CSV.03 |
Knowledge/ Understanding |
Students design, conduct and report on an equilibrium experiment;
written test. |
Some of the planning
notes below relate to the content of the unit while others are suggested to
help establish routines in this first unit of the course.
·
Follow all board
policies/procedures for the safe handling and disposal of chemicals and ensure
proper laboratory safety (goggles, gloves, ventilation) for all lab activities.
·
Provide reminder,
hints, and personal reflection time on a continual basis for students to
generate possible research questions/ideas for the Final Assessment Task.
·
Promote
independent learning skills by encouraging students to accept increasing
responsibility for their work, e.g., check posted solutions, generate and
compare lesson/text notes, formulate scientific questions and participate in
peer assessment.
·
It may be
appropriate to use a lecture for content delivery occasionally to help better
prepare students for university teaching strategies.
·
If possible, book
class time in the library/resource centre and/or the computer lab.
·
This unit is rich
in problem-solving opportunities. Careful planning will be essential. Consult
with math teachers regarding problem-solving background and possible
additional/supporting activities; if needed, arrange for possible sharing of
the graphing calculators.
·
Collect exemplars
of student work, e.g., notes, lab reports, Final Assessment Report, etc. for
future reference.
·
Prepare solutions
required for the End-of-Unit Task, e.g., Ca(OH)2 and Ca(OH)2
with a dissolved calcium salt such as Ca(NO3)2 at least
one week prior to the activity.
·
This unit has a
larger proportion of laboratory explorations to better prepare students for the
Final Assessment Task.
·
Self- and peer
assessment can be used as a valuable component of the assessment for many of
the activities, especially when accompanied by clear criteria; evaluation and
assignment of marks remain the responsibility of the teacher.
Jaeger, Dave
and Suzanne Weisker. Holt Chemistry: Visualizing Matter Laboratory
Experiments. United States: Holt, Rinehart and Winston, Inc., 1996. ISBN 0-03-095284-0
Jenkins,
Frank, et al. Nelson Chemistry. Nelson Canada, 1993. ISBN 0-017-603863-9
Slater, Alan
and Geoff Rayner-Canham. Microscale Chemistry Laboratory Manual. Don
Mills, ON. Addison-Wesley Publishers Ltd., 1994. Teacher’s Edition ISBN
0-201-60216-4 and Student’s Edition ISBN 0-201-60215-6
Tocci,
Salvatore and Claudia Viehland. Holt Chemistry: Visualizing Matter.
United States: Holt, Rinehart and Winston, Inc., 1996. ISBN 0-03-000193-5
Tocci,
Salvatore and Claudia Viehland. Holt Chemistry: Visualizing Matter Study
Guide. United States: Holt, Rinehart and Winston, Inc., 1996. ISBN 0-03-095283-2
Toon,
Ernest R., et al. Foundations
of Chemistry. Canada: Holt,
Rinehart and Winston of Canada, Limited, 1990. ISBN 0-03-922287-X
BioChemLinks –
http://biochemlinks.com.
Lab safety,
teaching science, science-related careers Curriculum Services Canada
Ontario Curriculum Centre – http://www.curriculum.org
Grade 10 Academic Science Profile Note-Taking Styles
Science
Teachers’ Resource Center (Lapeer County Information Depot)
– http://chem.lapeer.org/Chem1Docs/Index.html
The Squier
Group – http://www-wilson.ucsd.edu/education/gchem/equilibrium/
Clearinghouse
For Science, Mathematics, and Environmental Education – http://www.ericse.org/
Mansfield
University – http://www.mnsfld.edu/~bganong/102.html
Wilton
Highschool Chemistry – http://www.chemistrycoach.com/
Chemistry
Learning Center – http://learn.chem.vt.edu/tutorials/organic/index.html
American
Chemical Society
– http://chemistry.org/portal/Chemistry?PID=acsdisplay.html&DOC=vc2\1rp\rp1_markers.html
– http://www.sasked.gov.sk.ca/docs/chemistry/mission2mars/ – equilibrium
activities
Time: 10.0
hours
This activity
introduces students to the concept of dynamic equilibrium. They carry out an
experiment to determine the equilibrium constant for a system, followed by
solving equilibrium problems involving concentrations of reactants and products
and Keq. There is an opportunity to incorporate the use of available
technology, e.g., graphing calculators and spectrophotometers. Students develop
an understanding of Le Chatelier’s principle and use it to predict the
direction in which a system at equilibrium will shift when volume, pressure,
concentration, or temperature is changed, and to investigate how it may be
applied to optimize the production of industrial chemicals. Students review the
expectations for senior formal laboratory writing, in preparation for the
End-of-Unit and Final Performance Task.
Strand(s): Chemical Systems and Equilibrium
Learning
Expectations
CSV.01 - demonstrate
an understanding of the concept of chemical equilibrium, Le Chatelier’s
principle, and solution equilibria;
CSV.02 - investigate
the behaviour of different equilibrium systems, and solve problems involving
the law of chemical equilibrium;
CSV.03 - explain the
importance of chemical equilibrium in various systems, including ecological,
biological, and technological systems;
CS1.01 - illustrate
the concept of dynamic equilibrium with reference to systems such as
liquid-vapour equilibrium, weak electrolytes in solution, and chemical
reactions;
CS1.02 - demonstrate
an understanding of the law of chemical equilibrium as it applies to the
concentrations of the reactants and products at equilibrium;
CS1.03 - demonstrate an understanding of how Le Châtelier’s principle can predict the direction in which a system at equilibrium will shift when volume, pressure, concentration, or temperature is changed;
CS1.07 - define constant expressions; such as Ksp, Kw, Ka, and Kb;
CS2.01 - use
appropriate vocabulary to communicate ideas, procedures, and results related to
chemical systems and equilibrium;
CS2.02 - apply Le
Chatelier’s principle to predict how various factors affect a chemical system
at equilibrium, and confirm their predictions through experimentation;
CS2.03 - carry out
experiments to determine equilibrium constants;
CS2.06 - solve
equilibrium problems involving concentrations of reactants and products and Keq;
CS3.01 - explain how
equilibrium principles may be applied to optimize the production of industrial
chemicals;
SIS.01 - demonstrate
an understanding of safe laboratory practices by selecting and applying
appropriate techniques for handling, storing, and disposing of laboratory
materials, and using appropriate personal protection;
SIS.02 - select
appropriate instruments and use them effectively and accurately in collecting
observations and data;
SIS.03 - demonstrate
the skills required to plan and carry out investigations using laboratory
equipment safely, effectively, and accurately;
SIS.04 - demonstrate
a knowledge of emergency laboratory procedures;
SIS.05 - select and
use appropriate numeric, symbolic, graphical, and linguistic modes of
representation to communicate scientific ideas, plans, and experimental
results;
SIS.07 - communicate
the procedures and results of investigations for specific purposes by
displaying evidence and information, either in writing or using a computer, in
various forms, including flow charts, tables, graphs, and laboratory reports;
SIS.08 - express the
result of any calculation involving experimental data to the appropriate number
of decimal places or significant figures;
SIS.09 - select and
use appropriate SI units.
·
Understanding of
the Solutions and Solubility unit from SCH3U
·
Ability to solve
quadratic equations
·
Review and follow
all board regulations for the safe handling and disposal of chemicals, e.g.,
nitric acid. Teachers should consult (WHMIS) Material Safety Data Sheets for
appropriate treatment of sensitivities to substances being used in the
laboratory.
·
Gather samples of
relevant versus irrelevant or testable versus not testable research questions.
·
Prepare a
diagnostic quiz based on information from SCH3U if desired for this unit.
·
Based on the
outcome of the diagnostic assessment the teacher may wish to develop
independent study packages to help strengthen student background knowledge.
·
Gather and
prepare materials required for the following Activities: 1.1.3 - straws of
different diameter, 50 mL graduated cylinders; 1.1.4 - iodine and bromine
tubes, sodium chloride, acetic acid, calcium carbonate; 1.1.6 - hydrated cobalt
chloride, chromate/dichromate solutions etc.; 1.1.8 - pipettes, volumetric
flasks, spectrophotometers if available, Fe(NO3)3, KSCN,
nitric acid.
·
Suggested
Note-Taking Styles are provided in the Grade 10 Academic Profile Teacher
Support Material - page 3.
·
Prepare questions
(and solutions) that incorporate practical applications and career components
for the following Activities: 1.1.7 and 1.1.9.
·
Prepare lesson
notes for Activity 1.1.5.
·
Plan such that
the entire first period may be used to stimulate student interest, e.g., Act
1.1.1 Carousel Activity.
1.1.1 Student
Activity: Students rotate
through a carousel of activities to help the teacher assess prior knowledge and
prepare a review of concepts and skills required for this unit.
Teacher
Facilitation: The teacher
prepares a carousel of activities including hands-on and pen-and-paper
activities, based on material covered in SCH3U, e.g., binary nomenclature; mole
calculations; concentration calculations; solubility rules; processes involved
in dissolving compounds; identifying ionic and covalent compounds; titration
skills and net ionic equations; formulae of various acids and bases;
Bronsted-Lowry and Arrhenius definitions of acids and bases; writing equations
for dissociation of acids and bases; operational definition of pH;
saturated/unsaturated/super-saturated solution. Depending on the outcomes of
the diagnostic activity, the teacher may wish to offer support material to be
completed independently.
1.1.2
Student Activity: Students are
introduced to the assessment and evaluation strategies for the course, including
the midterm examination (if planned) to take place after the second unit and
the nature of the End-of-Unit Task. The End-of-Unit Task (Act 1.6) requires
students to use their knowledge of Ksp and the common ion effect to
design and conduct an experiment. The Final Assessment Task provides senior
students with the opportunity to demonstrate their Knowledge and Inquiry,
Communication and Making Connections skills at a pre-university level. Students
formulate their own research question, keep a log of their time, design and
conduct the experiment, and communicate their research in a formal lab report.
Students review a rubric and format for a senior level formal laboratory
report. In preparation for the Final Assessment Task, students complete a
T-chart comparing relevant versus irrelevant, or testable versus not testable
research questions. Time is allowed for students to ask clarification
questions.
Teacher
Facilitation: The teacher
reviews the four categories in the Achievement Chart, and emphasizes the importance
of independent inquiry skills for the End-of-Unit Task. Assist students with
the comparison chart by providing some criteria for an appropriate research
question. It is important to guide students to generate a research question for
the Final Assessment Task, preferably by the end of the second unit. Their
question should relate to or extend upon the topics of study in the course. Be
prepared to provide hints to generate appropriate research questions throughout
the course. The teacher prepares a handout outlining the format for a formal
laboratory report and a corresponding rubric. Suggestions for creating the
rubric are found in the Appendix. The teacher recommends that students keep the
rubric and format outline accessible in their notes.
1.1.3
Student Activity: Students
work with a partner to construct a physical analogue for an equilibrium system.
Each student gathers a 50 mL graduated cylinder and a straw (both straws should
be identical). One student labels the graduated cylinder ‘Reactant’ and adds 50
mL of water. The other student labels the cylinder ‘Product’ and leaves it
empty. Both students place the straw in the graduated cylinder until the bottom
of the straw touches the bottom of the cylinder. They then transfer water from
their graduated cylinders simultaneously, using one index finger to retain
water in the straw. There will be no water transferred from the Product to
Reactant containers during the first trial. Students record the volumes of the
Reactant and Product after each trial and plot the data as a line graph (plot
the Reactant and Product volumes on the same graph). Students formulate
questions, design a procedure, and conduct a lab investigating how changing
various factors may impact the physical analogue of the equilibrium system that
they created. They then analyse and compare the graphical data.
Teacher
Facilitation: The teacher
provides instructions for the first part of the activity and encourages
students to formulate questions investigating how changing various factors may
impact the equilibrium system, e.g., starting with equal volumes of Reactant
and Product, using straws with different diameters, using two straws in one
direction only, etc. Graphing calculators could be used if available. The
teacher uses the class results to introduce and explain the concept of
equilibrium and to discuss factors that may prevent a reaction from reaching
completion.
1.1.4 Student Activity: Students review the criteria for the
Observation section of a formal lab report. They then design their own
observation chart and collect data while investigating dynamic equilibrium at
various lab stations. Students assess one another’s observation charts.
Teacher
Facilitation: As part of the
progression towards producing independent learners, the teacher discusses
expectations for an efficient observation chart with the students, by referring
to a rubric or other recording tool. The teacher then sets up a variety of lab
stations investigating chemical and physical equilibrium systems, e.g., Cr2O72-
and CrO42-, N2O4 and NO2,
equilibrium of soluble salt in solvent (NaCl in water), slightly soluble salt
in solvent (CaCO3 in water), liquid-vapour equilibrium (bromine
tubes), solid-vapour equilibrium (iodine tubes), weak electrolytes in solution.
1.1.5 Student
Activity: Students participate
in a class discussion about various Note-Taking Styles, e.g., graphic
organizers, point form, paragraph form, embedded notes. They generate their own
notes based on a teacher-directed lesson about equilibrium and compare them
with the teacher’s notes.
Teacher
Facilitation: The teacher may
wish to direct students to the Grade 10 Academic Profile Teacher Support
Material – page 3 on Note Taking Styles and participate in a brief discussion.
The teacher directs a lesson on dynamic equilibrium systems including
equilibrium constant expressions, and the differences among between Keq,
Kp and Kc. The teacher may post lecture notes as a
reference and learning tool for students. Collect exemplars from students for
future reference material.
1.1.6
Student Activity: Students
review the assessment for the Procedure and Result sections of a formal lab
report prior to the activity. They investigate Le Chatelier’s principle by
designing and conducting a lab to analyse the effect of changing various
factors, e.g., temperature, concentration, volume and pressure, on different
chemical equilibrium systems. Students participate in a discussion about Le
Chatelier’s Principle.
Teacher
Facilitation: The teacher
reviews requirements for a Formal Laboratory Report and ensures required
materials are available for the experiments, e.g., hydrated cobalt chloride to
observe the impact of temperature changes; chromate/dichromate to observe the
impact of pH changes, etc. The teacher leads a discussion to summarize student
results and reviews Le Chatelier’s principle.
1.1.7
Student Activity: Students
complete problems based on Le Chatelier’s Principle. They research the
application of Le Chatelier’s Principle to optimize production of industrial
chemicals, e.g., ammonia, sulphuric acid. Working in small groups, students
discuss their findings.
Teacher
Facilitation: The teacher
assigns problems incorporating practical applications of Le Chatelier’s
Principle and possible career connections. Solutions to the problems are posted
and students are given an opportunity to ask questions. The teacher may wish to
book time in the library and/or computer room to assist students with their
research.
1.1.8
Student Activity: Students
vary the equilibrium concentrations of a chemical system to qualitatively
investigate the effect on chemical equilibrium and to quantitatively determine
the equilibrium constant of the system. They compare their results with each
other and expected values.
Teacher
Facilitation: There is an opportunity
for the teacher to incorporate technology into this activity, i.e.,
Spectrophotometric Determination of the Equilibrium Constant (see Resources).
1.1.9
Student Activity: Students
participate in a class discussion about the results of Act. 1.1.8. They discuss
possible sources of error. Students solve equilibrium problems involving
reactant/product concentrations and equilibrium constants.
Teacher
Facilitation: The teacher
leads the class in a discussion about Act.1.1.8 and encourages students to formulate
ideas about possible sources or error. The teacher provides students with
sample solutions to Keq problems. Assign questions involving
concentrations of reactants and products and equilibrium constants. The teacher
may encourage the use of graphing calculators and the quadratic equation to
analyse Keq equations. Solutions should be posted for students to
self-assess. The teacher may collect some problems for evaluation or provide a
quiz.
A question-answer sheet and a checklist assessing skills could accompany the diagnostic activity to determine the students’ incoming abilities. The teacher could assess one or two categories for each of the four experiments, e.g., Act 1.1.3 - Designing a Procedure and Tables and Figures, Act 1.1.4 - Observations, Act.1.1.6 - Procedure and Results, Act.1.1.8 - Discussion. Peer- and self-assessment could be used for self-generated notes. This activity provides an opportunity to assess and give feedback to students on their note-taking abilities and inquiry skills including laboratory writing skills, which they may apply in the Final Assessment Task. This activity provides many opportunities to assess the students’ Scientific Investigative Skills to help set the tone early in the course. Solutions to selected problems may be evaluated; evaluation of a quiz would serve the same purpose.
Reports (Inquiry, Communication, Making
Connections)
Problem Set or Quiz (Knowledge/Understanding, Making Connections,
Communication)
·
Allow increased
time for the completion of problems or reduce the number of questions as
appropriate for some students.
·
Establish a
glossary of terms that might be found in notes, texts, and problems.
·
Include diagrams
with problems.
·
Alternative note-taking
methods such as using a tape recorder can be used.
–
http://129.93.84.115/Chemistry/DoChem/DoChem115.html
Le Chatelier’s Principle
–
http://chem.lapeer.org/Chem2Docs/KeqLab.html
Spectrophotometric determination of equilibrium constant
– http://www.cvgs.k12.va.us/research/paper/question.htm
Criteria for a relevant research question
Time: 2.0 hours
This activity
introduces students to changes in entropy associated with chemical and physical
processes and the tendency of reactions to achieve minimum energy and maximum
entropy. Students investigate the role entropy plays in the spread and
elimination of pollutants such as PCBs. They peer assess and check
self-generated notes against the teacher’s to help develop confidence in their
abilities to work independently.
Strand(s): Chemical Systems and Equilibrium
Learning
Expectations
CS1.04 - identify,
in qualitative terms, entropy changes associated with chemical and physical processes;
CS1.05 - describe
the tendency of reactions to achieve minimum energy and maximum entropy.
·
Understanding of
physical/chemical changes and endothermic/exothermic reactions.
·
Prepare lesson
notes on entropy.
·
Prepare a rubric
for peer assessment of entropy notes.
·
The teacher may
wish to gather and prepare materials required for Activity 1.2.1- NaHCO3,
bunsen burner, ice, concentrated H2SO4.
·
The teacher
should follow all board regulations for the safe handling and disposal of
chemicals, e.g., sulphuric acid.
1.2.1
Student Activity: Students
generate their own notes from a teacher demonstration and teacher directed
lesson on entropy. Students peer-assess their notes in class and may compare
with teacher notes outside of class time. They complete assigned reading and
questions.
Teacher
Facilitation: Use a
demonstration to identify entropy changes associated with physical and chemical
processes, e.g., compare the entropies of the solid, liquid, and gaseous states
of a substance, concentrated sulphuric acid in water, decomposition of sodium
bicarbonate and provide students with an opportunity to formulate and ask
questions. Direct a lesson to emphasize that reactions have a tendency to achieve
minimum energy and maximum entropy and that entropy is the driving force behind
endothermic reactions. Assign problems incorporating environmental issues,
e.g., the difficulty associated with eliminating a pollutant such as PCB
because of the enormous energy requirement and generation of disorder.
This activity is an opportunity for peer assessment; in addition, provide feedback to students on their note-taking skills.
Notes
(Knowledge/Understanding, Communication)
·
Continue to add
terms to glossary.
·
Display posters
of different note-taking styles, with a description of pluses and minuses for
each method.
·
Use a tape
recorder for note taking.
Science
Teachers’ Resource Centre Lapeer County Information Depot
– http://learn.chem.vt.edu/tutorials/
Time: 6.0 hours
Students perform an
experiment to determine the Ksp value of a slightly soluble salt.
Students solve a variety of problems involving Ksp including
predicting the formation of precipitates and determining the molar solubility
of a pure substance in a solution of a common ion. The application and effects
of solubility in a variety of contexts are discussed. Students generate their
own notes and check posted solutions.
Strand(s): Chemical Systems and Equilibrium
Learning
Expectations
CS2.01 - use
appropriate vocabulary to communicate ideas, procedures, and results related to
chemical systems and equilibrium (e.g., homogeneous, common ion, Ka
value);
CS2.03 - carry out
experiments to determine equilibrium constants (e.g., Keq for iron
[III] thiocyanate, Ksp for calcium hydroxide, Ka for
acetic acid);
CS2.04 - calculate
the molar solubility of a pure substance in water or in a solution of a common
ion, given the solubility product constant (Ksp), and vice versa;
CS2.05 - predict the
formation of precipitates by using the solubility product constant;
CS2.06 - solve
equilibrium problems involving concentrations of reactants and products and the
following quantities: Keq, Ksp, Ka, Kb,
pH, pOH;
CS3.02 - identify
effects of solubility on biological systems (e.g., kidney stones, dissolved
gases in the circulatory system of divers, the use of barium sulfate in medical
diagnosis);
SIS.01 - demonstrate
an understanding of safe laboratory practices by selecting and applying
appropriate techniques for handling, storing, and disposing of laboratory
materials, and using appropriate personal protection;
SIS.02 - select
appropriate instruments and use them effectively and accurately in collecting
observations and data;
SIS.03 - demonstrate
the skills required to plan and carry out investigations using laboratory
equipment safely, effectively, and accurately;
SIS.08 - express the
result of any calculation involving experimental data to the appropriate number
of decimal places or significant figures;
SIS.09 - select and
use appropriate SI units;
SIS.10 - identify
and describe science-and technology-based careers related to the subject area
under study.
·
Quantities in
Chemical Reactions and Solutions and Solubility from SCH3U.
·
Review and follow
all local Board regulations for the safe handling and disposal of chemicals.
·
Gather materials
for the following Activities: 1.3.2-silver acetate or lead(II) chloride needs
to be prepared several days in advance of the activity; 1.3.4-ammonium
hydroxide, ammonium chloride and phenolphthalein and a petri dish.
·
Have students
prepare Act 1.3.2 24 hours in advance of making quantitative observations to
ensure that all the silver or lead(II) ions have had the opportunity to react.
·
Due to toxic
nature of lead(II) chloride, it is suggested that calcium hydroxide be used.
·
Gather and
prepare questions (and solutions) that incorporate practical applications and
career components for the following Activities: 1.3.3 and 1.3.4.
·
Take proper
safety precautions when using concentrated stock solutions.
·
Prepare notes on
the applications of solubility product constants.
Act 1.3.1
Student Activity: Students
generate their own notes from a lesson on the equilibrium constant for slightly
soluble ionic substances and its applications in the environment, society and
industry. They investigate possible related careers. Students set up their lab
for Act. 1.3.2 and, based on the lab procedure provided by the teacher, prepare
their own observation tables. Students assess each other’s lesson notes outside
class time.
Teacher
Facilitation: To provide a
context for learning the solubility product constant, the teacher refers to
applications of equilibrium solubility such as kidney stones, dissolved gases
in the circulatory system of divers, the use of barium sulfate in medical
diagnosis, the formation of stalactites and stalagmites as found in the
Bonnechere Caves in Ontario, hard water and water softeners, refining nickel,
developing camera film, and the massive deposits of limestone and gypsum as
oceans dry up. A more detailed treatment of these applications can occur in Act
1.3.5 once students have mastered the concept of Ksp and the common
ion effect. Based on the results of the diagnostic quiz in Act 1.1.2, the
teacher uses the students’ prior knowledge of unsaturated, saturated and
supersaturated solutions and links it to chemical equilibrium systems. Students
will apply this knowledge in Act 1.3.2 to determine an actual Ksp
value. The teacher provides students with the lab procedure for Act 1.3.2.
1.3.2
Student Activity: Students
conduct a lab to quantitatively determine the Ksp value for a
relatively insoluble salt, e.g., silver acetate by displacement with copper
wire, lead(II) chloride with a strip of zinc metal.
Teacher
Facilitation: The teacher
could set up the analysis section of this lab to lead students step-by-step to
arrive at the expression and value for the Ksp of silver acetate or
lead(II) chloride. The teacher may quickly check students’ observation tables.
1.3.3
Student Activity: Students
solve Ksp questions.
Teacher
Facilitation: The teacher should
choose Ksp problems involving concentration, including molar
solubility of pure substances in water. Problems could be collected for
evaluation.
1.3.4
Student Activity: Students
take notes on the common ion effect, precipitation reactions, predicting precipitate
formation using Ksp data and applications from a teacher-directed
lesson. Students solve problems involving common ion effect and compare their
answers to posted solutions.
Teacher
Facilitation: The teacher
could do a quick demonstration of common ion effect such as how an excess of
ammonium ions reduces the concentration of hydroxide ions. To do so place a
petri dish on an overhead projector, and fill it halfway with 1mol/L ammonium
hydroxide. Add two drops of phenolphthalein. The solution should be red. Stir a
little solid ammonium chloride into the solution; the red colour will
disappear. The ammonium ions suppress the ionization of the ammonium hydroxide.
An example of a practical use of equilibrium constants is in the use of barium
sulfate as an X-ray contrast medium. Doctors must make certain that almost no
poisonous barium ions are present to dissolve in a person’s body fluids.
Knowing the solubility product constant for barium sulfate, calculations are
made to determine the amount of barium sulfate needed for the procedure. To
ensure that the concentration of barium ions will not exceed the safety level,
a soluble salt such as sodium sulfate, which contributes sulfate ions, is added
to increase the sulfate ion concentration and reduce the barium ion
concentration. Because sulfate ion is present in both barium sulfate and sodium
sulfate, sulfate is the common ion present in both substances dissolved in the
solution. Some students will have trouble grasping the concept of the common
ion effect. First, remind them that because the solubility of barium sulfate is
very low, it is not involved in the equation for the solubility product
constant. It follows that the product of the two ion concentrations is equal to
the constant, Ksp. A constant value cannot change, so if one of the
concentrations rises, the other must drop. By means of this principle, the
common ion effect can be used to increase or decrease the concentration of a
chosen ion.
1.3.5 Student Activity: Students can generate their own notes from a
more detailed lesson on the practical applications of solubility equilibrium.
Teacher
Facilitation: The teacher
prepares lesson notes for those applications mentioned in Activity 1.3.1. The
teacher administers a quiz based on Solubility Equilibrium.
A lab report (emphasizing the abstract) for the experiment would be appropriate. Short quiz questions on a variety of Ksp problems should be used to determine the students’ abilities and/or a problem set could be collected.
Report (Inquiry, Communication,
Making Connections)
Quiz (Knowledge/Understanding, Making Connections, Communication)
Problem Set (Knowledge/Understanding, Making Connections, Communication)
·
Use alternative
note-taking methods such as a tape recorder.
·
Reduce the number
of repetitive problems.
·
Add terms to
glossary.
·
Organize problems
according to type and provide model solutions for each type.
Newton,
David. Chemistry Problems. Portland, Maine: J. Weston Walch, Publisher,
1977.
World of
Chemistry, TVO Video Series,
1988 – World of Chemistry: Driving Forces
Time: 6.0 hours
Students are
introduced to the key concept of dissociation constants as a measure of the
relative strength of weak acids and bases. They conduct experiments to find the
Ka of a weak acid and the pH of salts of weak acids and bases. Students are
provided with an opportunity to practise preparing solutions and using
titration skills that may be applied in the End-of-Unit and Final Assessment
Tasks. They solve a variety of problems involving acid-base equilibrium and
titration data.
Strand(s): Chemical Systems and Equilibrium
Learning
Expectations
CS2.01 - use appropriate
vocabulary to communicate ideas, procedures, and results related to chemical
systems and equilibrium;
CS2.03 - carry out
experiments to determine equilibrium constants (e.g., Keq for iron
[III] thiocyanate, Ksp for calcium hydroxide, Ka for
acetic acid);
CS2.06 - solve
equilibrium problems involving concentrations of reactants and products and the
following quantities: Keq, Ksp, Ka, Kb,
pH, pOH;
CS2.07 - predict, in
qualitative terms, whether a solution of a specific salt will be acidic, basic,
or neutral;
CS2.08 - solve
problems involving acid-base titration data and the pH at the equivalence
point;
SIS.01 - demonstrate an understanding of safe laboratory practices by
selecting and applying appropriate techniques for handling, storing, and
disposing of laboratory materials, and using appropriate personal protection;
SIS.02 - select
appropriate instruments and use them effectively and accurately in collecting
observations and data;
SIS.03 - demonstrate
the skills required to plan and carry out investigations using laboratory
equipment safely, effectively, and accurately;
SIS.09 - select and
use appropriate SI units.
·
Properties of
acids and bases
·
Bronsted-Lowry
and Arrhenius definitions of acids and bases
·
The difference
between strong and weak acids and bases in terms of degree of dissociation
·
The operational
definition of pH
·
Writing equations
for dissociation of acids and bases
·
Basic titration
skills
·
Gather and
prepare materials for the following Activities: 1.4.1 – solutions of strong and
weak acids and bases, pH meters/probes/paper; 1.4.3 – a number of salts,
distilled water and pH meters/probes/paper and a fill-in-the blank worksheet;
1.4.5 – concentrated acid and base solutions, pH meters/probes/paper, indicators
and titration apparatus; 1.6 – End-of-Unit Task solutions of Ca(OH)2
and Ca(OH)2 with dissolved calcium salt.
·
Prepare a rubric
to assess the Abstract and Discussion sections of a senior-level formal lab
report. Some suggested criterion statements are provided in the Appendix.
·
Prepare a
peer-assessment checklist for titration skills for use in Act 1.4.5.
·
Gather and
prepare questions (and solutions) that incorporate practical applications and
career components for the following Activities: 1.4.2, 1.4.3, and 1.4.6.
·
Take proper
safety precautions when using concentrated stock solutions.
·
Follow all board
regulations for the safe handling and disposal of chemicals.
1.4.1
Student Activity: Students
could generate their own notes to distinguish between strong and weak acids and
bases using the concept of equilibrium. Through a teacher-directed lesson, they
are introduced to the equilibrium constants Ka, and Kb
and Kw.
Teacher
Facilitation: Based on the
results of the diagnostic quiz in Act 1.1.2, the teacher uses students’ prior
knowledge to explain how dissociation constants are a measure of the relative
strength of weak acids and bases. The teacher may wish to do a demonstration as
a visual aid using pH meters/probes/paper and a variety of solutions of acids
and bases to compare strong and weak acids and bases using the concept of
equilibrium. This leads to a discussion on equilibrium constants. Remind
students that they worked with equilibrium constants in Act 1.1.9 and that the
acid/base/water dissociation constants are set up the same way.
1.4.2
Student Activity. Students
solve problems calculating pH, [H3O+], pOH, [OH-], Ka,
Kb, and Kw.
Teacher Facilitation: Direct a lesson to provide sample questions
and solutions for problems calculating pH, [H3O+], pOH,
[OH-], Ka, Kb, and Kw. Post answers
for the problem set and provide students with an opportunity to ask questions
pertaining to the problems. Suggest that experiments to determine equilibrium
constants, Kb, Ka for weak acids and bases at various
temperatures would be a straightforward Final Assessment Task project.
1.4.3 Student Activity: Students prepare aqueous solutions of several
salts and measure the pH of the solutions. Students record their results and
then apply their knowledge to homework questions. Students compare their
answers to posted solutions.
Teacher
Facilitation: In order to
encourage students to make connections, the teacher can extend the topic of
salt hydrolysis with a discussion of the practical application of antacids to
relieve acid indigestion. Excess stomach acid must be treated with a basic
solution in order for neutralization to occur. The teacher could bring in some
common antacids to determine their active ingredient, and ask students to show
by equations how these particular substances can act as bases. Post answers for
the problems and provide students with an opportunity to ask questions
pertaining to the problems.
1.4.4
Student Activity: Under
teacher guidance, students practise and participate in peer assessment of
titration skills including appropriate use and care of burettes. They prepare
their own dilutions of an acetic acid solution of known concentration. They
then design and conduct a titration to confirm the pH of the solution of acetic
acid they have prepared and to calculate Ka.
Teacher
Facilitation: The teacher
prepares a solution of acetic acid of known concentration for use in the
dilutions and a standard base solution for titration.
1.4.5
Student Activity: Students
participate in a class discussion about Act 1.4.4. Students work together to
solve problems focussing on the use of titration curves for strong and weak
acids and bases to determine the pH of the equivalence point. Students complete
a written quiz based on Act 1.4 – Acid Base Equilibrium.
Teacher
Facilitation: The teacher
discusses the results and conclusion from Act 1.4.4. Post answers for the
problems and provide students with an opportunity to ask questions pertaining
to the problems. Error analysis can also be discussed here. The teacher
administers a quiz based on Acid Base Equilibrium.
A laboratory report for the experiment emphasizing the Introduction and Discussion would be appropriate. The teacher could use a rubric as an assessment tool. Students should participate in peer assessment of titration skills. Post or discuss answers to the problems on acid base equilibrium and salt hydrolysis in order to provide feedback to the students. Use a written quiz based on acid base equilibrium to determine the students’ skills.
Report (Inquiry,
Communication, Making Connections)
Quiz and/or Problem Set (Knowledge/Understanding, Making Connections,
Communication)
·
Use alternative
note-taking methods such as a tape recorder.
·
Allow sufficient
time for the completion of problems and for students to perform titrations
until results are replicated.
·
Set up a buddy
system for students during problem-solving sessions.
·
Include
illustrations to show proper technique for using the equipment found in this
unit.
Acids and Bases, TVO video series, 1987.
Chem tutor –
http://www.chemtutor.com/acid.htm#buffmat
- Acid/base and titration activities
World of
Chemistry, TVO Video Series,
1988 – World of Chemistry: Proton of Chemistry
Time: 2.5 hours
Students make
observations and collect data from a teacher demonstration to help formulate a
definition of a buffer system. They enhance their understanding of the
characteristics and components of a buffer solution by completing an assigned
reading and questions. Students participate in a seminar activity to research
and report on how buffering action affects our daily lives.
Strand(s): Chemical Systems and Equilibrium
Learning
Expectations
CSV.01 - demonstrate
an understanding of the concept of chemical equilibrium, Le Chatelier’s
principle, and solution equilibria;
CSV.03 - explain the
importance of chemical equilibrium in various systems, including ecological,
biological, and technological systems;
CS1.09 - describe
the characteristics and components of a buffer solution;
CS3.03 - explain how
buffering action affects our daily lives, using examples;
SIS.06 - compile and
interpret data or other information gathered from print, laboratory, and
electronic sources, including Internet sites, to research a topic, solve a
problem, or support an opinion.
·
Identify and
explain properties of acids, bases, and solutions from SCH3U and SNC2D.
·
Follow all board
regulations for the safe handling and disposal of chemicals.
·
Gather and
prepare materials required for Act. 1.5.1: acetic acid, sodium acetate,
concentrated acid, concentrated base, pH probe(s) if available.
·
Book time in the
resource centre and/or computer room.
·
Gather and
prepare questions about buffer systems that incorporate practical applications.
1.5.1
Student Activity: Students
design their own observation chart and collect data from a teacher demonstration
illustrating the components and basic characteristics of a buffer system. They
generate a definition of a buffer system and hypothesize how it works. Students
enhance their understanding by completing an assigned reading and questions.
Teacher
Facilitation: The teacher
prepares solutions of a sodium acetate/acetic acid buffer system
(6 × 50 mL) and use a pH probe or an indicator to demonstrate the effect of
adding small volumes of concentrated acid and base. Remind students to think
about the common ion effect and how weak acids function. Direct students to do
additional reading and answer assigned questions. Post answers for the problems
and provide students with an opportunity to ask questions.
1.5.2
Student Activity: Students
research/review material on how buffering action affects our daily lives, e.g.,
acidosis/alkalosis, buffered medications. Working in small groups they further
their understanding by discussing their findings.
Teacher
Facilitation: The teacher may
book time in the resource centre and/or computer room. Facilitate peer
assessment of group work.
A short quiz could
be used to ensure that students understand the characteristics and components
of a buffer system. It would be appropriate to have students participate in
peer assessment of group work skills.
Quiz
(Knowledge/Understanding, Making Connections)
Research and/or Report (Inquiry, Communication, Making Connections)
·
Have a range of
reading materials for answering assigned questions.
·
Continue the use
of a glossary.
Chem tutor –
http://www.chemtutor.com/acid.htm#buffmat - Buffer activities
Time: 3.5 hours
This activity is
composed of two distinct parts. The first part provides students with an
opportunity to combine knowledge and skills acquired throughout the unit to
investigate a system at equilibrium. Students design a procedure, make their
own solutions, perform a titration, collect and analyse data and communicate
their results in a formal laboratory report. The second part is a written test
used to assess students’ knowledge and abilities to make connections.
Strand(s): Chemical Systems and Equilibrium
Learning Expectations
CSV.01 - demonstrate
an understanding of the concept of chemical equilibrium, Le Chatelier’s
principle, and solution equilibria;
CSV.02 - investigate
the behaviour of different equilibrium systems, and solve problems involving
the law of chemical equilibrium;
CSV.03 - explain the
importance of chemical equilibrium in various systems, including ecological,
biological, and technological systems;
SIS.01 - demonstrate
an understanding of safe laboratory practices by selecting and applying
appropriate techniques for handling, storing, and disposing of laboratory
materials, and using appropriate personal protection;
SIS.02 - select
appropriate instruments and use them effectively and accurately in collecting
observations and data;
SIS.03 - demonstrate
the skills required to plan and carry out investigations using laboratory
equipment safely, effectively, and accurately.
· Students should be familiar with standardizing acids and bases with titration, the common ion effect, Keq, Ksp and Ka and quantitatively determining Keq and Ksp.
·
Prepare the
following solutions at least one week in advance: Ca(OH)2 and Ca(OH)2
with dissolved calcium salt such as Ca(NO3)2.
·
Take proper
safety precautions when using concentrated stock solutions.
·
Follow all board
regulations for the safe handling and disposal of chemicals.
·
Ensure
appropriate materials are available: titration apparatus, filter paper,
indicators, thermometers, concentrated hydrochloric acid.
·
Prepare a written
test that assesses students’ knowledge and ability to make connections.
1.6.1
Student Activity: Students use
their knowledge of Ksp to design and conduct an experiment to
determine the solubility product constant for a semi-soluble salt, such as
Ca(OH)2. Students should then use their knowledge of the common ion
effect to determine the additional calcium ion concentration in an equilibrium
system, e.g., Ca(OH)2 containing dissolved calcium salt. This
activity provides students with an opportunity to link skills and knowledge
used throughout the unit, such as, using appropriate safety procedures,
applying Le Chatelier’s principle, and performing a titration.
Teacher
Facilitation: Prepare two
solutions, Ca(OH)2 and Ca(OH)2 with dissolved calcium
salt, at least one week prior to use. Review the evaluation scheme with the
class. Encourage students to consider using methods or techniques to maximize
accuracy, e.g., filtering the Ca(OH)2 solutions, using three trials
etc. Ca(OH)2 is corrosive. Remind students to handle and dispose of
chemicals safely. The teacher may also allot time during the activity to assess
the students’ practical skills.
1.6.2
Student Activity: Students
complete a written test.
Teacher
Facilitation: The teacher
generates a test focussing on Knowledge and Making Connections.
A formal laboratory report for the experiment would be appropriate, since it helps prepare the student for the Final Assessment Task. A written test including a variety of types of questions could be used to assess the student’s knowledge and ability to make connections.
Report (Inquiry,
Communication, Making Connections)
Unit Test (Knowledge/Understanding, Making Connections)
·
Provide
identified students with extra time for the written test.
·
See
Accommodations in the Course Overview.
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