Save Baby Paul: Teacher's Notes
Activity: How Cotton Burns
Safety: First and Foremost
If you choose to do any of the testing as a demonstration or as hands-on activities, it's essential to follow all safety precautions to the utmost. Students may need to be reminded that burns are painful and can be disfiguring, and trying any of these experiments (especially the cellulose nitrate, even as commercial flash paper sold in magic stores) on a larger scale can be fatal. It is our hope that in providing video footage of the more dangerous demonstrations, the need for individuals to do these in person will be nil, and thus students will be able to see the chemistry and learn from it without any risk whatsoever.
We offer this site as an educational tool. WE ARE NOT RESPONSIBLE FOR ANY INJURY OR DAMAGE CAUSED TO ANY PERSON, DIRECTLY OR INDIRECTLY, RELATING TO ANY OF THE DEMOS OR EXPERIMENTS LISTED AT THIS SITE. YOU ARE WHOLLY RESPONSIBLE FOR YOUR SAFETY.
- Wear safety goggles at all times.
- Provide a safety shield for protection of the students and of you.
- Perform all experiments and demonstrations in a well-ventilated area, in open, still air. (That is, if you do this outdoors, a breezy day can be unpredictable and hazardous.)
- Never ignite anything in a sealed or closed container.
- To examine the combustion of a cotton ball
- To prepare a "flame retardant" cotton ball
- To compare the combustion properties of the treated and untreated cotton balls
- To describe the properties of sodium bicarbonate as a flame retardant
National Science Education Standards: Content Standards
This activity fulfills the following within the Content Standards: 9-12
- Content Standard A: Science as Inquiry
Students conduct an investigation of the effect of a simple flame retardant on cotton, and tie their observations and results to the molecular properties of the materials used. Opportunities may be made available for further investigations based upon questions that arise from their experiments. (For example, an extension examines the effect of surface area.)
Safety must be an integral component of their investigations. If the videos are used rather than hands-on experimentation, discuss with the students how these experiments are carried out safely.
- Content Standard B: Physical Science
- Structure and Properties of Matter
- Chemical Reactions
- Cotton balls - these need to be real cotton, not the synthetic cotton balls
- Baking soda - sodium bicarbonate
- Fireplace lighter or Bunsen burner
- Balance - optional; to obtain the mass of sodium bicarbonate added to the cotton ball
- Have the students place an untreated cotton ball on a noncombustible surface (in a hood if available).
- Have the students ignite the cotton ball. The students should monitor the amount of time that is required for the cotton ball to ignite (start burning).
- Have the students observe the combustion of the cotton ball after the ignition source (the lighter or Bunsen burner) is removed. Have the students describe their observations in writing, noting as many detailed changes as possible.
- Have the students prepare a treated cotton ball by dusting a cotton ball with baking soda. The experiment may be modified by having the students weigh the cotton ball before and after dusting with baking soda and then determining the amount of baking soda that has been applied.
- Have the students repeat the combustion test on the treated cotton ball.
- How is the ignition of the treated cotton ball different from the untreated cotton ball?
- How is the combustion of the treated cotton ball different from the untreated cotton ball?
- What property (or properties) of baking soda would explain these observations?
- Would you expect a cotton ball treated with flour to behave in the same manner as the cotton ball treated with baking soda?
- How might the surface area be important to ignition and combustion?
- To examine the effect of surface area, the experiment can be repeated with cotton string and a piece of cotton fleece that have been dusted with baking soda.
- Are the changes observed due to the fact that the baking soda is a powder? Try treating a cotton ball by soaking it in a saturated solution of baking soda in water. Have the students weigh the cotton ball before and again after it's dry to determine how much baking soda was adsorbed. (Was the uptake of baking soda similar to that of the powder?)
- Do other powders behave the same way? Try treating a cotton ball with flour, baking powder, baby powder, powdered soap, etc.
DO NOT try any of the following: gasoline, fingernail polish remover, lighter fluid or any known flammable liquid or solid. These can produce a very flammable or even explosive cotton ball.