Kinetics

2 Mar 2020

ChemCrafter

Submitted by Michelle Personick, Wesleyan University
Evaluation Methods: 

Student learning is not assessed directly after the activity, but rather is assessed indirectly through student performance on related homework and exam questions. More specifically, the second section of the exams in my general chemistry course always asks students to "provide a concise (but complete) explanation or rationalization for [some number] of the following statements." This section is particularly suited to assessing the learning goals above.

Evaluation Results: 

This activity was recently introduced, and student performance has not been evaluated yet.

Description: 

ChemCrafter, from the Science History Institute (formerly the Chemical Heritage Foundation), is a free iPad app that mimics a classic chemistry set. It is set up as a game, with three sections: reactions with water, reactions with acid, and salts. The app shows the progress of the reaction (smoke, color change, etc.) when two elements are mixed in a reaction vessel, and also gives the change in enthalpy of the reaction.

Pros: It's a safe and fun way to demonstrate some visually exciting chemical reactions. It's free and the graphics are high quality. The app projects well on a large screen using a standard classroom projector.

Cons: Accessing later sections of reactions requires completion of the previous sections, and there is some artificial gating of chemical and glassware replenishment behind wait times. As a result, it's best used as a demo rather than as a dry lab. It's also only available for the iPad.

 

Prerequisites: 
Corequisites: 
Course Level: 
Learning Goals: 

Students should be able to explain the difference between thermodynamics and kinetics.

Students should be able to explain why even thermodynamically favorable reactions sometimes do not proceed on an observable timescale.

Students should be able to explain why heat is sometimes necessary to make a highly exothermic reaction proceed.

Implementation Notes: 

Once everything is unlocked, it's possible to set up any reaction using the chemicals in the given "set" for each category of reaction. I use ChemCrafter in my second semester general chemistry course to transition from a unit on reactions of ions in aqueous solution (hydration/hydrolysis, Bronsted acid/base and hard-soft acid base principles of solubility/reactivity, etc.) to a unit on kinetics. I show a series of reactions from the salt section that the students would expect to have roughly increasing enthalpies of lattice formation based on the Born-Lande equation:

[Note: All reactants are in their elemental form in the app, so the enthalpies of formation aren't truly lattice energies.]

2 Na + Cl2 --> 2 NaCl   (1+ cation with a 1- anion) 

2 K + F2 --> 2 KF (1+ cation with a 1- anion)

Zn + Cl2 --> 2 ZnCl(2+ cation wtih a 1- anion)

These combinations were selected because their reactions in the app become increasingly dramatic (and colorful) in this order. I then show the students a set of reactions that they would expect to be even more exciting, but which don't actually proceed without heat. They hold their breath for the first one to react.

Zn + S --> ZnS (2+ cation with a 2- anion)

2 Al + 3 I2 --> 2 AlI3 (3+ cation with a 1- anion)

The app provides an option for heating these mixtures of elements with a bunsen burner, and then they react dramatically. At this point, we're ready to discuss the difference between thermodynamics--which is all they've seen up to this point--and kinetics.

Time Required: 
5-10 minutes of class time
16 Jan 2020

Time-Integrated Rate Laws and the Stability of Gold(III) Anticancer Compounds

Submitted by Jack F Eichler, University of California, Riverside
Evaluation Methods: 

1) Performance on the pre-lecture online quiz

2) Performance on the in-class activity (clicker scores or hand-graded worksheet)

 

Evaluation Results: 

Students generally score on average 70% or higher on the pre-lecdure quiz, and on average 70% or more of students correctly answer the in-class clicker questions. 

Description: 

This is a flipped classroom module that covers the concepts of time-integrated rate laws. This activity is designed to be done at the end of the typical second quarter/second semester general chemistry kinetics unit. Students will be expected to have learned the following concepts prior to completing this activity:

a) how instantaneous rates of reactions are determined by measuring changes in concentration of reactants and/or products at the beginning of the reaction;

b) understanding basic rate laws and how rate laws are determined for a chemical reaction using instantaneous rates;

c) understanding why the rates of reactions slow down as the time of reaction increases.

Acknowledgement: This material is based upon work supported by the National Science Foundation under Grant No. 1504989. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

 

Learning Goals: 

Students are expected to achieve the following learning goals:

a) conceptually understand how time-integrated rates laws can be used to describe the kinetics of a chemical reaction;

b) use time-integrated rate laws to determine the rate constant for a first or second order reaction;

c) use time-integrated rate laws to determine the half-life of a decomposition reaction;

d) use Excel to plot time-integrated rate laws and generate best-fit linear trend lines.

 

Corequisites: 
Equipment needs: 

Students need a laptop or tablet device capable of operating a spreadsheet/graphing program. 

Course Level: 
Prerequisites: 
Topics Covered: 
Subdiscipline: 
Implementation Notes: 

See attached instructor notes. 

Time Required: 
50-80 minutes
25 Jul 2019

1FLO: One Figure Learning Objects

Submitted by Chip Nataro, Lafayette College
Corequisites: 
8 Jun 2019

VIPEr Fellows 2019 Workshop Favorites

Submitted by Barbara Reisner, James Madison University

During our first fellows workshop, the first cohort of VIPEr fellows pulled together learning objects that they've used and liked or want to try the next time they teach their inorganic courses.

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