Of Jiwei Li and Tatiana Vrabie
Chemistry, Grade 12, University Preparation SCH4U
Concept presentation: Rate of Reaction
Summary
Background Information
Slow Reaction
Fast Reaction
http://en.wikipedia.org/wiki/Reaction_rate
The reaction rate represents the speed of reaction or the speed of chemical change. It may be
measured by the amount (usually expressed in moles) or concentration of substance
transformed/changed/produced in the unit of time.
For example,
2Mg(s) + O2 → 2 MgO(s)
In this reaction, we can observe how much time is necessary for all amount of magnesium to
react with oxygen.
The average rate (r) of a reaction is expressed as the number of moles of Mg used up or MgO
formed, divided by the total reaction time:
r
c
Mg  MgO 


t
t
t
The instantaneous rate of reaction is the speed at particular moment (point) of reaction, can be
obtained from the slopes of the tangents to the line of concentration vs time.
Chemists are equipped with different methods to measure the rates of reactions, which are
merely quantitative analysis of substance vs. time. The most important are volume for gases with
low solubility, conductivity for ions, spectrophotometry for light absorbing substances in
solutions.
The most important factor for the speed of reaction is concentration of reactant. It is a common
sense that more particles (molecules, ions, atoms) we have at the beginning of change (reaction),
the more changed particle we can observe in the unit of time. That’s why speed is a function of
reactant initial concentration. The name of function is Rate Law and reactions are classified by
Rate Law in order 0, 1, 2.
For reaction aX + bY → product, the Rate Law or Rate Equation is:
m
n
r  k X  Y  ,
where {X}, {Y} are known initial concentrations and
k –rate constant; m, n –exponents or individual orders of reaction, determined empirically.
Overall order of reaction is equal to m+n.
Five factors are affecting Rates of Reaction (RR):
 Nature of reactant
 Concentration raise increases RR
 Temperature raise increases RR
 Presence of a Catalyst increases RR
 Surface area raise increases RR
Why all these factors are important is explained by Collision Theory. The main concepts of
Collision Theory are:




The average kinetic energy of particle is proportional to temperature of sample
Collisions of particles is a must for reaction to occur
Only collision of particles with sufficient energy leads to successful reaction
RR depends on frequency of collisions and the fraction of successful collisions
A reaction mechanism is a series of steps that make up an overall reaction. Each step, called an
elementary reaction, involves a single molecular event, such as a simple collision between
atoms, molecules, or ions. Usually the elementary reaction called rate-determining step
determines the overall rate.
Molecularity
Elementary step
rate
-> products
rate
-> products
rate
+ A -> products rate
B -> products rate
+ C -> products rate
1
A -> products
2
A + A
A + B
3
A + A
A + 2
A + B
Rate law
=
=
=
=
=
=
k
k
k
k
k
k
[A]
[A]2
[A] [B]
[A]3
[A] [B]2
[A] [B] [C]
A catalyst is a substance that increases the rate of a chemical reaction without being consumed
by the reaction. A catalyst works by lowering the activation energy of a reaction so that a larger
fraction of the reactants have sufficient energy to react.
A homogeneous catalyst exists in the same phase as the reactants. Homogeneous catalysts most
often catalyze gaseous and aqueous reactions. A heterogeneous catalyst exists in a phase that is
different from the phase of the reaction it catalyzes.
Curriculum expectations
D2.8 plan and conduct an inquiry to determine how various factors (e.g., change in temperature,
addition of a catalyst, increase in surface area of a solid reactant) affect the rate of a chemical
reaction [IP, PR, AI]
D3.5 explain, using collision theory and potential energy diagrams, how factors such as
temperature, the surface area of the reactants, the nature of the reactants, the addition of
catalysts, and the concentration of the solution control the rate of a chemical reaction
Advance Preparation
Prerequisite for Rate of Reaction unit is knowledge about Enthalpy and Heats of Reaction as
well as Hess’s Law and Thermochemical Equations.
Many lessons include computer simulations, therefore computers availability should be arranged
in advance.
For Lab Activities students should be asked to bring lab coats, goggles and gloves. Video
demonstration require teacher to check up Internet and projector function in the classroom
For the Project or Thought Lab, teacher should come to class prepared with several suggestions
of catalysts and enzymes. Therefore, teacher may need to do some initial research.
Teaching Ideas / Strategies / Lesson sequence
Lesson Title
& Number
1. Expressing
and
Measuring
Reaction
Rates
Classroom activities
Learning/Teac
hing Strategy
Thinking about slow and fast reactions, for example:
rusting of metals, weathering of rocks (e.g. limestone rocks
being weathered by water), combustion.
Brainstorm,
Whole class
activity
Class Demo: Mg and Fe reactions with HCl. Students
figure out reactions equations and predict the RR.
http://www.infoplease.com/chemistry/simlab/singlehcl.html
lab simulation, single replacement reactions with different
metals.
Demonstration
Cooperative
groups
Computer
simulation
Expression of RR, average, instantaneous rate, calculating
the rates.
Direct
instruction
Assessment
strategy,
Achievement
category
AF*Anecdotal
notes, Questions
and Answers,
K/U
AF,
Peer evaluation,
T, A, C
AA,
Flash-cards main
points, Q&A,
Calculations of RR. Practice p.364#1, 2, 3{1}
Measuring RR. Reactions that produce a Gas, involves
Ions, change Color
2. The Rate
Law and
Order of
Reaction
Homework: p.365#4, 5, 6; p.366#1
Independent
work
Video http://www.youtube.com/watch?v=kjKyEdrVXJA
demo”the rate vs conc.”
Investigation 6.3.1. The Iodine Clock Reaction. {1} to find
empirically RR as function of initial concentration and
formulate Rate Law equation.
http://www2.ucdsb.on.ca/tiss/stretton/chem2/ratelab1.htm
worksheets for Lab.
Rate law, Rate Law equation, order of reactions (individual
and overall), Half-life.
Lab. Activity in
cooperative
groups
http://www.chm.davidson.edu/vce/kinetics/DifferentialRate
Laws.html
Finding the order of reaction and Half-life. Practice: p.
377#2, 3. {1}; p.381#3
3. Theories
of
Reaction
Rates
Problem
Solving
In cooperative
groups
Lecture brief
Factors affecting RR, animation.
http://www.concord.org/activities/chemical-reactions-andstoichiometry
Gizmo Worksheet “Collision Theory” and animations
(Activities A and B)
http://www.explorelearning.com/index.cfm?method=cReso
urce.dspDetail&ResourceID=553
Concepts of the Collision Theory, Kinetic energy,
activation energy, endo- and exo- termic reactions,
theoretical effect of conc, surface area, temperature.
Homework:Practice p.387#1 {1}
Anticipation
Guide,
independent
reading and
discussion in
group
Computer
simulation
(order of
reaction, halflife)
Problem
solving in
cooperative
groups
Computer
simulation
(temp., conc.,
surface area
factors).
Problem
solving on
worksheets
Think-PairShare
Lecture brief
Concept Map
http://jsteinwe
bsite.yolasite.
com
K/U
AA,
Numerical
Problem Solving
T/I, A, C
AA, Q&A on
methods of
measuring
K/U, T
AO,
Self assessment,
K/U, T, A
AO,
Lab Report,
Performance
checklist, and onthe-spot
questioning
K/U, A, C, T/I
AF, AA,
Checklist on
Anticipation
Guide Questions,
K/U, T
AA,
Q&A,
K/U
AO,
Numeric Problem
solving, peer
evaluation,
T/I, A, C, K/U
AA,
Worksheet
checklist,
T/I, A, C
AO,
Short Quiz,
K/U, A, C, T/I
AO,
4. Reaction
Mechanis
ms and
Catalysts
action
Independent
work
Self-assessment
K/U, A, C
Lecturing the concepts of reaction mechanism,
elementary reaction, rate–determining step.
Lecturing
Questioning
K/U, C
Groups working on the practice problems
p.301 #17-20{2}
Jig-saw activity
AO
Participation
K/U, C
Lecturing the concepts of catalyst (heterogeneous and
homogeneous) and how a catalyst works.
Brainstorming
Computer
animation
http://www.concord.org/activities/catalysts
Homework: section review p.309 #6-9
5. Lab
investigati
on
Inquiry-based lab.
In this lab activity students will examine some of the key
factors that influence the rate of a reaction:
 nature of reactants - particle size 
 temperature 
 concentration
 catalysts
Independent
Work
Group work
Lab activity
Critical thinking
AO,
Self-assessment
K/U, T/I, C
AO
Lab
performance
K/U, T/I, A, C
Students are given the lab materials and then asked to
design the procedure by themselves.
The lab can be obtained from:
http://www.saskschools.ca/curr_content/chem30_05/2
_kinetics/labs/rate_factors.pdf
AO
Rating Scale
K/U, T/I, C
Homework: Lab Report
6. Project
Developing a Bulletin About Catalyst and Enzymes
Design an information bulletin to inform the
community about the use of catalysts or enzymes in
Canadian industries.
The project should contain the following analysis:
For catalyst:
(a) What is the chemical formula of the catalyst? Is the catalyst
heterogeneous or homogeneous?
(b) What process does the catalyst speed up? Include products,
reactants, the reaction mechanism (if possible), and information
about the uncatalyzed reaction.
(c) What technology is required to support the catalyzed reaction
(for example, the design of a catalytic converter)?
(d) What is the importance and relevance, to Canadians, of the
industry associated with the catalyst?
For enzyme:
(a) What chemical process is the enzyme involved in?
(b) How does the enzyme fit into an overall biological process?
(c) Are there any ways in which the enzyme can be prevented
Students STSE
project
presentation
Do the research
on internet or in
library, collect
data and
information and
evaluate the
information
AO
The bulletin
should be
interesting,
visually
attractive ,
factual, and
aimed at a wide
audience.
Students’
designed rubric
for multiple
intelligence
(song, essay,
diary entry,
from doing its job? Explain.
(d) Is the enzyme mass-produced by industry? If so, how? For
what purpose is it mass-produced?
visual design,
role play
performance,
A, C
* Note: Assessment for Learning-AF, as Learning – AA, of Learning - AO
Potential students Difficulties and Possible Solutions
Potential Difficulties
Possible Solutions
Students may mix up the
stoichiometric coefficients
with reaction order
To show in the lab. that reaction order is determined empirically and may
be non-integer number, differentiate wit colors.
Give some example of non-integers order
http://chemwiki.ucdavis.edu/Physical_Chemistry/Kinetics/Reaction_Rates
/Definition_of_Reaction_Order
Give the students equation of a straight line and repeat how it may be
found from plot.
Finding Mathematical
expression for Iodine Clock
Rate of Reaction.
Understanding that the
frequency of collisions is not
the function of temperature
Misconception of catalyst and
enzyme
Contrast and show by animation that frequency does not increase
essentially with temperature, but average energy of particle does, which is
important for reaction to occur.
Asking students to brainstorm a list of what they already know. Address
that catalysts and enzymes are regenerated unchanged at the end of a
reaction, and they usually increase the rate of a reaction.
Differentiated Assessment
Differentiated Assessment should be provided to evaluate the learning outcome of Differentiated
Teaching Strategies.
Diagnostic Assessment empowers students as well as teacher with better knowledge of their
strength and weaknesses and helps create more successful learning plan. Diagnostic or
Assessment for learning is done at the beginning of the unit in the form anecdotal notes during
brainstorm, Q&A before and after Demo, checklist on answers on Anticipation Guide.
Assessments as learning were used permanently as Numerical problems Solving, Questions and
Answers, Worksheet answers checklist. This type of assessment serves for identification of
difficulties, misconceptions and current results of students learning.
Assessment of learning was performed as self –assessment, Lab. Report, Performance Checklist,
peer evaluation in numeric problem solving, short quiz. The purpose of AO is to gain evidence of
students’ achievements in some tasks and skills.
The project of “Bulletin” can be alternated as a “Thought Lab”. In the lab, teacher helps students
create a list of catalysts that are used in industries and a list of enzymes. Students choose one
industrial catalyst and one enzyme (specific biological catalyst, which is protein by chemical
nature) and use electronic and print resources to research the substances. They also can write a
song, essay, diary entry, make visual design on poster or even create animation, role play
performance, calculations and logical construction to fulfill the task.
Applications and Societal Issues/Implications
Many reactions that produce useful compounds proceed too slowly to be used in industries.
Some reactions need to be carried out at high temperatures or pressures to proceed quickly.
These conditions, however, are often expensive to maintain. Therefore, chemists and engineers
use catalysts to speed up the reactions in order to obtain products at a reasonable rate and under
mild conditions. Similarly, without the presence of enzymes many necessary biological reactions
would proceed too slowly to sustain life. The primary action of most drug and vitamins is related
to biochemical reactions rate, which is controlled through enzyme regulation.
For specific purposes is beneficial to slow down chemical reactions, especially in food industry
(food preservation reactants, storage in the cold conditions, in the liquid nitrogen, inert gases),
inhibition of microorganisms growth, some surgical processes need cooling of body tissues.
The project of “Bulletin” or “Thought Lab” is designed to study some applications and societal
issues.
Accommodations








consult individual student IEPs for specific accommodation and modifications in teaching
methodologies
when grouping students take into account availability of peer help
help students with creation of graphic organisers
be cooperative with special education providers about tests, assignments, etc.
permit ESL/ESD students use translators and extend timelines for them
record keywords on a board
provide appropriate level resources for reading
use more visual aids
http://resources.curriculum.org/csc/library/profiles/12/html/SCH4UP.htm
Safety Considerations
•
Teacher review the safety rules before lab and Students should have their lab coats, goggles and
gloves ready for use.
•
As students will use computers to complete virtual labs and research, it is important that teacher
ensures that students are using computer in an appropriate way.
Annotated References
1. Van Kessel, H., Jenkins, F., Davies, L., Plumb, D., Di Giuseppe, M., Lantz, O., & Tompkins,
D. (2002). Nelson chemistry 12. Toronto, Ontario: Nelson Thomson Learning.
2. Mustoe, F., Jansen M.P., Webb, M., Hayhoe, C., Cherkas, A., Gaylor, J. (2002) Chemistry
12 McGraw-Hill Ryerson
3. FHSST Authors. The Free High School Science Texts: Textbooks for High School Students
Studying the Sciences. Chemistry, Grades 10 – 12. 2008 www.fhsst.org
4. http://www.woodrow.org/teachers/chemistry/exchange/topics/woc/woc14.html Collision
Theory Quiz
5.
6. http://www.chm.davidson.edu/vce/kinetics/ReactionRates.html reaction rates simulations
with background information.
7. http://www.infoplease.com/chemistry/simlab/singlehcl.html Virtual lab. simulation, single
replacement reactions
8. http://www.concord.org/activities/chemical-reactions-and-stoichiometry Effect of
temperature, concentration and surface area on RR, animation
9. http://www.explorelearning.com/index.cfm?method=cResource.dspDetail&ResourceID=553
Gizmos worksheets and computer simulations on Collision Theory and other chemistry
curriculum topics.
10. http://chemwiki.ucdavis.edu/Physical_Chemistry/Kinetics/Reaction_Rates/Definition_of_Re
action_Order Non-integer order of Chemical reaction, problem solving
11. http://www.youtube.com/watch?v=kjKyEdrVXJA Demo of H2O2 decomposition rate at
concentration 3% and 30%
12. http://jsteinwebsite.yolasite.com Chemistry teacher Janet Stein website, some course
outlines, worksheets, concept maps
13. http://www2.ucdsb.on.ca/tiss/stretton/chem2/ratelab1.htm Worksheet for lab. “The Iodine
Clock Reaction”
14. http://www.chemguide.co.uk/physical/basicrates/ordermech.html#top rates of reaction,
diagrams and explanations
15. http://www.saskschools.ca/curr_content/chem30_05/2_kinetics/labs/rate_factors.pdf Factors
Affecting Reaction Rate
16. http://www.concord.org/activities/catalysts activity addresses homogeneous catalysis
Additional web resources
http://resources.curriculum.org/csc/library/profiles/12/html/SCH4UP.htm Chem 12 all units
Plans
http://www.virtlab.com/Chapters/Chapter7.aspx virt lab, needs subscription payment
http://www.aeei.gov.sk.ca/Default.aspx?DN=ab27fca2-315f-4e5c-8cd1-cc60061a2475 science
http://phet.colorado.edu/en/simulation/reactions-and-rates Interactive Simulations on rate of
reaction
http://www.youtube.com/watch?v=A_PhvIktMOw&feature=relatedt video about Catalysis:
introduce the concepts of Catalysis and how we use Catalysts in everyday scenarios
http://www.slideshare.net/JSlinkyNY/reaction-rate concept presentation
Concept Map (Rate of Reactions)
SCH4U
Curriculum Specific Expectations:
D3.5 explain, using collision theory and potential energy diagram, how factors
such as temperature, the surface area of the reactants, the nature of the
reactants, the addition of catalysts, and the concentration of the solution
control the rate of chemical reaction.
Specific for this activity:
Learning expectation: Demonstrate and refine understanding of “Rate of
Reactions” concept and its connection to other concepts.
Time: 30 minutes, as a review activity
Materials:
 A1 size paper – 1 for each students’ group
 Set of small images with the names related to Rate of Reactions
concepts – 1 set per group
 Glue
Teaching strategies:


Cooperative groups (3-4 students, numbered heads together) with
assigned roles and numbers (Record Keeper, Materials Handler, Time
Manager, Presenter)
Concept Map
Task:
Teacher will give explanation on Assessment format and materials
distribution -5 min
Students will construct Concept Map on A1 size paper by using the given
set of images and glue - 10 min
Students would indicate on arrow descriptive relationship between
concepts
Each group will present their Concept Map and numbered heads would
debates or stand by their way of presentation – 15 min
For example:
Temperature →→→→Rate of Reaction (“Positive correlation” above the
arrow)
Assessment:



Anecdotal notes as formative assessment
Fool mark will be granted to all group members with condition that all
members of group can explain Map design at minimum acceptable level
Achievement Rubric: K/U, T/I, C
Collision Theory Quiz
http://www.woodrow.org/teachers/chemistry/exchange/topics/woc/
woc14.html
1. What is the basis of all chemical reactions?
2. What is necessary for successful collisions?
3. What is meant by activation energy?
4. How are activation energies affected by catalysts?
5. What is true about a catalyst at the end of a chemical reaction?
6. What is meant by equilibrium?
7. What does Le Chatelier's Principle tell us about equilibrium reactions?
8. What is the reaction involved in the Haber Process?
9. Why is this reaction important?
10. What conditions are used to increase the yield in the Haber Process?
Answer Key
1. What is the basis of all chemical reactions?
Collisions of particles that have the minimum energy to react.
2. What is necessary for successful collisions?
The collisions must be of sufficient energy to react.
3. What is meant by activation energy?
The minimum amount of energy needed to bring about a reaction.
4. How are activation energies affected by catalysts?
They are lowered.
5. What is true about a catalyst at the end of a chemical reaction?
It remains unchanged.
6. What is meant by equilibrium?
Two opposing reactions that occur at equal rates.
7. What does Le Chatelier's Principle tell us about equilibrium reactions?
The reaction may be ``shifted'' when stresses are applied to the system.
8. What is the reaction involved in the Haber Process?
2 H2 + N2
2 NH3
9. Why is this reaction important?
Ammonia is an important starting material in the manufacture of
fertilizers and explosives.
10. What conditions are used to increase the yield in the Haber Process?
The temperature was kept relatively low, the pressure was kept high
Collision Theory
http://jsteinwebsite.yolasite.com
Complete this concept map using these terms: collision theory,
Temperature, concentration (of reactant molecules), reaction rates,
catalyst, amount of energy
_____________________
explained by
influenced by
____________
____________
______________
_____________ _________
Complete this sentence:
1. Increasing the temperature will ____________ the number of
effective collisions.
Write your answer to these questions in complete sentences:
2. Keeping a lightstick in the freezer prolongs its life because:
3. What is meant by an “effective collision”?
4. In addition to temperature, explain how a catalyst can affect
the rate of a chemical reaction.