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Stop & Go Gases (3 Favorites)

DEMONSTRATION in Chemical Change, Catalysts, Acid Base Reactions, Combustion, Chemical Change. Last updated September 6, 2019.


Summary

In this demo, students will witness the ability of carbon dioxide to extinguish a flame and oxygen to feed a flame.

Resource Type

Demo

Grade Level

Middle and high school

Objectives

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

  • Recognize that combustion reactions can only take place in the presence of oxygen.
  • Understand that carbon dioxide extinguishes a flame.
  • Understand the role of a catalyst

Chemistry Topics

This lesson supports students’ understanding of

  • Combustion
  • Gases
  • Chemical change
  • Catalysts
  • Acid base reactions

Time

Teacher Preparation: 5 minutes

Lesson: 5 minutes

Materials

  • 2 Erlenmeyer Flasks (250 mL)Stop go materials
  • 10ml graduated cylinder
  • Matches or a portable butane lighter
  • Wooden splints
  • Commercial vinegar solution
  • Solid baking soda
  • Hydrogen peroxide solution, 3%
  • 2% yeast suspension (you can also use solid manganese dioxide or solid potassium iodide)

Safety

Teacher Notes

  • This demonstration is an easy way to demonstrate the chemical properties of two gases involved in combustion. It also shows students two examples of how gases can be produced in chemical reactions.
  • One is an acid-base reaction (followed by rapid decomposition of one of the products), and the other is a Stop go1decomposition reaction that involves a catalyst.
  • There are a variety of ways in which to generate oxygen gas. You can add about 5 mL of a yeast suspension to the hydrogen peroxide solution. Another way to generate oxygen is to add a small quantity (0.5–1 g) of either solid manganese dioxide or solid potassium iodide to the hydrogen peroxide solution. This lab uses the yeast suspension.
  • Prepare yeast suspension: Add 1 gram of active dry yeast to 10ml of distilled and mix or shake well to make suspension.

Lesson

  1. Add 1.5 – 2 grams of solid baking soda to one of the flasks. The exact amount is not critical. Stop go2
  2. Measure 10ml of vinegar into a 10ml graduated cylinder.
  3. Add about 15–20 mL of 3% hydrogen peroxide to the second flask.
  4. Measure 5ml of yeast suspension into a 10ml graduated cylinder.
  5. Pour the vinegar into the flask that contains baking soda. The goal is to produce a small quantity of carbon dioxide gas in the flask. The foam that may be produced should not overflow out of the flask.
  6. Pour the yeast suspension into the 3% hydrogen peroxide. The goal is to produce a small quantity of oxygen gas in the flask. The foam that may be produced should not overflow out of the flask.
  1. Light a wood splint and allow it to burn for a few seconds. If the tip of the wood splint begins to glow red, this Stop go3will make it easier to relight the splint after it is extinguished.
  2. Quickly insert the flaming wood splint into the flask with carbon dioxide gas. The splint should not touch the liquid in the flask. The flame will become extinguished because of the carbon dioxide gas. The tip of the wood splint should still glow at this point. If it is not, you need to use a match or a lighter to heat the tip of the splint until it glows.
  3. Insert the glowing wood splint into the flask with oxygen gas. The splint should not touch the liquid in the flask. The glowing splint should reignite because of the presence of oxygen gas.
  4. This process can be repeated over again several times. The flaming splint will go out in the carbon dioxide, and the glowing splint will relight in the oxygen. Stop when the wood splint becomes too short to use safely.
  5. Pour the contents of the two flasks and the remaining yeast suspension down the sink and rinsed with plenty of water.