Temperature and the Rate of Chemical Reactions

Purpose

The purpose of this lab is for students to investigate the effect of temperature on the rate of a chemical reaction.

Key Science Topics

Kinetic Molecular Theory of Heat
Energy transformation (e.g., chemical energy to light {or radiant} energy)
Electron energy levels, absorption and emission
Fluorescence

Grade Level

Physical Science, Grades 6-9

Student Prior Knowledge

Students should be able to define the Kinetic Molecular Theory of Heat.
Students should be familiar with the Bohr model of the atom and electron energy levels.
While it would be helpful if students were familiar with electron energy levels and absorption/emission of photons, this activity could be used to introduce that concept.

Materials

Each lab group should have the following:

Three beakers labeled A, B, and C
Thermometer
Three glow sticks that are the same size, brand, and color
Hot, room temperature, and cold water

I have used mini glow sticks up to the regular-sized glow sticks. Be sure to have extra on hand as some glow sticks will not react. After Halloween is a good time to stock up on glow sticks at a bargain price. Science supply stores (especially on-line) and party stores are good sources as well.

This may also be done as a teacher demo and have students record the data.

Resources

Lesson Guide, student worksheet and teacher answer key (PDF)

Suggestions

I usually use this lab as an introduction to atomic spectra—a challenging topic for middle school, high school and college students. This lab is a good review of how the Bohr model; while it is an incomplete description of the atom, is a good model for explaining electron energy levels.

To explain electron energy levels, I use the standard climbing on a chair, then a lab table method. While standing on the ground, I explain that I am on the ground state. If I absorb just the right amount of energy, I will then have enough energy to hop up onto the chair. I then stand on the chair and ask my students if that required energy. Yes. Then I describe that if I absorb yet another packet of energy, I can move up to the second level. Or, I can hop down to the ground state and give off energy. If I hop down to the ground state, I emit a packet of energy which is a photon, or particle of light. I also mention that I can [theoretically, at least] go from the ground state directly up to the table (2^nd level). I can also jump directly from the table to the ground state and bypass the first state entirely [theoretically speaking again].