Module Overview
This module teaches fundamental concepts in chemical kinetics for General Chemistry using examples of water quality and water treatment. Key chemistry topics include concentration vs. time data; rate constants (k); reaction order; rate law expressions (including integrated rate laws); determining rates, rate laws, and rate constants from graphical and/or tabulated data; half-life; Arrhenius relationships; activation energy; reaction coordinate diagrams; and chemical mechanisms.
The context of this module ties closely to green and sustainable chemistry as well as the United Nations Sustainable Development Goal (UN-SDG) 6: Clean Water and Sanitation. Context-related topics include where water is sourced, trade-offs between disinfecting water and forming disinfection byproducts, and specific reactions important for water treatment. The module situates drinking water sources, drinking water treatment, and impacts of drinking water quality in an interconnected system.
To address prevalent misunderstandings in the field of kinetics, activities and concepts aim to clarify the relationship between equations, graphs, and the molecular viewpoint. Course material includes lecture slides (i.e., PowerPoint), small group or think-pair-share activities, guided exercises, and summative quiz or exam questions. The out-of-class activities include hands-on computer simulations based on a freely- accessible version of the Stella platform. These activities are meant to enhance student engagement with the material and facilitate the interpretation of kinetics graphs, data, and equations.
Module Goal
Students will understand the fundamental concepts of chemical kinetics, including understanding and application of key equations and interpretation of graphical and tabulated data. Students will be able to analyze how kinetics applies to real-world systems, such as water treatment and delivery.
Audience
First-semester general chemistry undergraduates
Class Time Requirement
Approximately three 50-minute class periods
Module Authors
Katherine B. Aubrecht, Stony Brook University; John B. Randazzo, North Park University
Module Summary
Assumed Prior Knowledge
Instructors may want to introduce systems-thinking concepts, such as SOCME diagrams prior to this module. Students should be able to demonstrate the following skills and concepts to successfully begin this module:
- Writing reactions
- Stoichiometry
- Solutions (including concentration)
Learning Objectives
Students will be able to:
- Explain how knowledge of rates of change is useful in the context of chemical reactions or other contexts.
- Determine initial, average, and instantaneous rate from change over time data.
- Explain what a rate constant is and how to determine its units.
- Describe parts of a rate law expression, e.g., rate = k[A]n.
- Write a rate expression in terms of change of concentration over change in time based on a balanced chemical equation.
- Use initial rates data to determine rate law, overall reaction order
- Use rate law expressions to determine how rate changes as concentration of reactants change.
- Using integrated rate expressions and graphical kinetic data for first and second order reactions, determine the order in a reactant and the value of the rate constant
- Interpret concentration vs. time, rate vs. time, and rate vs. concentration graphs, including how these graphs change for reactions of different orders and different rate constants.
- Use the first- and second- order integrated rate laws to calculate the concentration of reactant at a given reaction time.
- Explain the concept of half-life, how half-life is related to the rate constant, and use half-life to calculate concentrations over time given initial concentrations.
- Use the Arrhenius equation to determine how rate constant changes with temperature.
- Use rate constant vs. temperature data to calculate activation energy.
- Interpret reaction coordinate diagram, including identifying reactants, products, activation barriers, and intermediates.
- Describe the role of a catalyst in a chemical reaction.
- Explain the information given in a reaction mechanism and identify “reactants”, “products”, “intermediates”, and “catalysts” in a mechanism.
- Analyze if a proposed mechanism is consistent with a given chemical reaction and experimentally determined rate law expression.
- Explain, in general terms, where drinking water can come from, what harmful contaminants may be in it, and how it may be purified.
- Describe the trade-offs between disinfecting drinking water and forming disinfection byproducts.
- Describe how kinetic studies can be used to optimize drinking water treatment methods.
- Discuss the role of chemistry in achieving the UNSDGs, specifically UNSDG 6, clean water and sanitation.
- Use systems thinking to analyze how knowledge of rates of change (in different subsystems) contributes to availability and safety of drinking water.
Learning Environment and Context
The module PowerPoint slides can be given in a traditional lecture format. Formative assessments, especially Stella-based activities, may be best as out-of-class activities but could be adapted to in-class if student technology (i.e., computer with internet) is available. Summative assessment questions were written for an in-class exam or quiz.
Unit Overview
Unit 1: Drinking water treatment and connections to chemical kinetics
1.1 | A general overview of water treatment: Its importance in modern society; an introduction to the underlying chemistry of disinfection and formation of disinfection byproducts; and a discussion of kinetics in a broader sense as the rate of change over time, with examples in water usage. |
1.2 | Activity 1: First order reaction: formation of a disinfection byproduct. Guided homework to generate results from kinetics simulations using the Stella platform. This activity on a first-order reaction and asks students to analyze the equations and variables describing the reaction and the graphical results generated by the model. |
1.3 | Activity 2: Second order reaction: hydroxyl recombination. Guided homework to generate results from kinetics simulations using the Stella platform. This activity on a second-order reaction and asks students to analyze the equations and variables describing the reaction and the graphical results generated by the model. |
Unit 2: Kinetics nuts and bolts
2.1 | Presentation covering all fundamental concepts of kinetics appropriate for a General Chemistry class. Specific examples from the context of water treatment are included. |
2.2 | Activity 3: Temperature dependence of rate constants. Guided homework to generate results from kinetics simulations using the Stella platform. This activity is for a first-order process run at variable temperature. Students are asked to interpret results using the Arrhenius equation. |
2.3 | Activity 4: Deducing a mechanism. Activity asks students to determine which mechanism of phenol chlorination is consistent with experimental reaction order data. |
Unit 3: Supply of safe drinking water SOCME
3.1 | Single slide of Systems Oriented Concept Map Extension (SOCME) about safe drinking water, with subsystems: chemistry, toxicology, hydrology and hydrogeology, social and economic, and wastewater treatment and sanitation.er sense as the rate of change over time, with examples in water usage. |
3.2 | Activity 5: Data analysis water disinfection mechanism. Students are asked to analyze concentration and time data from a series of experiments testing the role of sunlight and natural organic matter in chlorination treatment of water. |
3.3 | Activity 6: Systems view of drinking water quality and quantity. Formative assessment focused on water treatment and delivery as a system. Asks students to analyze the safe supply of drinking water SOCME and to research where their local drinking water comes from and the challenges in their local area. |
Download Module
Kinetics Includes:
- Module Overview Document
- 3 Slide Decks
- 6 Learning Activities
- Formative & Summative Assessments
Copyright Statement
We encourage the reuse and dissemination of the material here for noncommercial purposes as long as attribution to the original material on the ACS site is retained. Material on this page is offered under a Creative Commons Attribution 3.0 License unless otherwise noted.
- Attribution required
- Allows remix of content
- Commercial use not allowed
About the Green Chemistry Module Project
The ACS Green Chemistry Instiute has partnered with chemistry instructors from over 45 institutions to develop green chemistry education resources for undergraduate students studying general and organic chemistry.