Summary

This lab uses the principles of chemical kinetics without using a chemical reaction. It’s an effective means to introduce the important relationship between concentration and time at an introductory level. Students will have the opportunity to analyze data and make important connections through graphing their data.

Grade Level

High school

Objectives

By the end of this lab, students should be able to

• Properly use a burette, and collect data using it.
• Plot the data collected in multiple ways.
• Recognize the graphical relationships for zeroth, first, and second order kinetics.
• Determine the value, from the most linear graphical data, for the constant, k, and the units for that constant.
• Use Excel to analyze data collected.

Chemistry Topics

This lab supports students’ understanding of

• Kinetics
• Reaction Rate
• Order of Reactions

Time

Teacher Preparation: 15 minutes

Lesson: 50 minutes

Materials

• Water
• Ring stand
• Burette clamp
• 50 mL burette
• 50 mL beaker
• Funnel
• Stopwatch or other timing device
• Access to computers with Excel or similar graphing program

Safety

• Always wear safety goggles when handling chemicals in the lab.
• Students should wash their hands thoroughly before leaving the lab.
• When students complete the lab, instruct them how to clean up their materials and dispose of any chemicals.

Teacher Notes

• The rate of a reaction can be represented through the concentration of the reactants and time. Reactions can go fast or slow. By determining the rate order for a reaction one can go on to predict what the concentration might be in 10 or 20 seconds or 10 or 20 years. For example the Chlorofluorocarbon molecules (CFC’s) in the atmosphere that threatens to ozone layer change at a very slow rate. Or some nuclear decay may take thousands of years. Although this activity does not represent CFC’s concentrations with time or any nuclear decay, it does provide students with the tools to conduct such analysis on real data.
• Students should be familiar with the rate order graphs prior to this lab. This video can serve as helpful background/review information “The Rate Law”, by Bozeman Science prior to class.
• This simple activity is a good precursor to lecture notes regarding the integrated rate laws. Students collect the data, graph the data, and then draw conclusions regarding reaction orders and the integrated rate laws.
• I find this method helps students internalize the concepts more readily than reading and lecture alone.

Variations/Additions to the lab:

• If you have access to lap timers, the data could be collected in two continuous runs setting a lap at each interval and save time.
• Students can collect the data through a continuous run method rather than the “refill” method as described in this lab procedure.
• Students could graph the data on graph paper rather than using Excel to make it a more mathematical activity.
• Extension activities:

CFC and other greenhouse gas data could be analyzed to provide a real world application using NOAA’s Annual Greenhouse Gas Index. An activity for a simpler application could link this NOAA activity to greenhouse gases.