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Potassium Permanganate Demo (7 Favorites)

DEMONSTRATION in Reaction Rate, Redox Reaction, Chemical Change, Exothermic & Endothermic. Last updated August 17, 2019.


Summary

In this demo, students witness two chemicals that take some time to react. The KMnO4 and glycerin come into contact and appear not to react, but then a flame results. This is an example of an exothermic redox reaction.

Grade Level

High school

AP Chemistry Curriculum Framework

This demonstration supports the following units, topics, and learning objectives:

  • Unit 4: Chemical Reactions
    • Topic 4.7: Types of Chemical Reactions
      • TRA-2.A: Identify a reaction as acid-base, oxidation-reduction, or precipitation.
  • Unit 6: Thermodynamics
    • Topic 6.1: Endothermic and Exothermic Processes
      • ENE-2.A: Explain the relationship between experimental observations and energy changes associated with a chemical or physical transformation.

Objectives

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

  • Recognize that a chemical change doesn’t have to happen immediately.
  • Understand that one chemical is giving up electrons and another chemical is accepting them (redox).
  • Realize that the resulting flame indicates an exothermic reaction.

Chemistry Topics

This lesson supports students’ understanding of

  • Chemical change
  • Redox reaction
  • Exothermic
  • Kinetics

Time

Teacher Preparation: 10 minutes

Lesson: 10 minutes

Materials

  • Powdered KMnO4
  • Paper towel
  • Water
  • Ceramic dish/evaporating dish (optional: use layer of sand)
  • Glycerin (glycerol)

Safety

  • Always wear safety goggles when handling chemicals in the lab.
  • It’s recommended to wear gloves when carrying out this demonstration.
  • Students should be warned not to approach the experiment area when the reaction is in progress. It takes a moment for the reaction to begin, so they may be tempted to lean in to get a closer look. Do not allow this to happen.
  • The reaction takes between 20 and 60 seconds to get going.
  • Always use caution around open flames. Keep flames away from flammable substances.
  • An operational fire extinguisher should be in the classroom.
  • This demonstration should be completed in the fume hood with the sash closed as sparks may be produced. Alternatively, using a polycarbonate shield to surround the reaction would also be beneficial.

Teacher Notes

  • Wet a paper towel and lay it flat on a flame resistant surface.
  • Put an evaporating dish upside down on top of the paper towel.
  • Pour a silver-dollar sized pile of powdered potassium permanganate onto the middle of the dish.
  • Make a divot with a pencil or a spoon so the powder looks like a volcano.
  • Fill the opening of the volcano with glycerin.
  • The reaction takes between 20 and 60 seconds to get going, and then it will smoke and burst into flames.
  • I have noticed that if you add too much glycerin it doesn't react.
  • Extensions to the kinetics of the reaction could be explored by changing the size of the divot, or not making a divot at all.