Chemistry Teachable TidbitSummer Institute

Randy, Brandi, Casey, Matt, Teresa

Teaching Tidbit Context

Our audience consists students in the second semester of a general chemistry course.

Typical UnitsUnit 1 – Intermolecular forces and SolutionsUnit 2 – Kinetics and EquilibriumUnit 3 – Thermodynamics

Learning Objectives1. Generate a model that describes a dynamic

equilibrium system 2. Compare and contrast concentration versus

time graphs for an equilibrium system3. Generate an equilibrium expression for a

reaction given the rate law expressions4. Relate the individual rate constants to the

equilibrium constant expression

Learning GoalStudents will understand and appreciate the relationship between kinetics and equilibrium.

t=0 min t=10 min t=20 min

Concentration Change over time

Imagine you are in your chemistry lab completing an experiment. Your reaction has run for 20 minutes and you have the above data. Each beaker above shows the concentrations of A and B. As a Group1. Draw a correctly formatted graph showing the change in

concentration of A and B over time.2. Predict: Draw the reaction beaker at t = 30 minutes.

Reaction: A B

t=0 min t=10 min t=20 min t=30 min t=100 min

Concentration Change over time

You then allow your reaction to go for up to 100 minutes. Modify your graph to include the new data. Discuss the change of concentration of A and B over time.

Reaction: A B

t=0 min t=10 min t=20 min t=30 min t=100 min

Concentration Change over time

As the reaction progresses, focus on the black outlined molecule converting between A and B.4. Discuss within your group whether the reaction has

stopped at 20 minutes. At 100 minutes?

Reaction: A B

At equilibrium, which of the following statements is true about the rates?

A. Rate of forward rxn > Rate of reverse rxnB. Rate of forward rxn = Rate of reverse rxnC. Rate of forward rxn < Rate of reverse rxnD. Rate of forward rxn =0, rate of reverse rxn = 0

Reaction: A B

Dynamic Equilibrium

1. Consider the kinetic data produced by monitoring the reversible conversion of Molecule A to Molecule B over time.

A

B

a) Propose a balanced chemical equation to explain these data.b) Generate the equilibrium expression for your proposed chemical

reaction.c) What concentrations would you expect for A and B at equilibrium?

Assessing Learning Objective 1 - Generate a model that describes a dynamic equilibrium system

SUMMATIVE ASSESSMENT #1 (High level HOC)

Reaction: A B

2. a) For the reaction below, circle the graph that best describes the change in concentration over time where Keq = 2.0

b) Explain the reasoning behind your choice.

A

B

Conc

entr

ation

TimeCo

ncen

trati

onTime

Conc

entr

ation

Time

Conc

entr

ation

Time

SUMMATIVE ASSESSMENT #2 (HOC)Assessing Learning Objective 2 - Compare and contrast concentration versus time graphs for an equilibrium system

Reaction: A B

1. Using the Graph above:a. What time are the concentrations of A and B equal?b. What time has the reaction reached equilibrium?

SUMMATIVE ASSESSMENT #3 (LOC)

A

B

Conc

entr

ation

Time0 10 20

Assessing Learning Objective 1 - Generate a model that describes a dynamic equilibrium system

Inclusive Teaching Strategies1. Engage more learning styles by:• using visual, auditory and tactile learning opportunities

2. Engage more personality types by:• working in small groups• asking one group member to report out

3. Make material accessible to include more abilities by:• simple diagrams without “scary molecules”• color choices for teaching materials

Normal Color Vision Red-Blind/Protanopia Vision

http://www.color-blindness.com/coblis-color-blindness-simulator/