DEMONSTRATION in Lab Safety. Last updated June 12, 2017.
In this demonstration, students discuss laboratory safety and observe corn starch being ignited.
Middle and high school
By the end of this lesson, students should be able to
- explain the importance of laboratory safety rules.
- verbalize reasons why laboratory procedures cannot be changed without first consulting their teacher.
This lesson supports students’ understanding of
- Lab safety
Teacher Preparation: 5–10 minutes
Lesson: 10–15 minutes
- Corn starch
- 1 Sheet of printer paper
- 100-mL beaker
- Bunsen burner
- Personal protective equipment (PPE)
- Always wear safety goggles when working with chemicals in a laboratory setting.
- Wear personal protective equipment and keep the area clear of flammables when working with flames.
- This is an engaging demonstration to reinforce the importance of laboratory safety rules.
- This demonstration is easy to set up, extremely cost effective, and students very much enjoy watching the flames.
Begin class by engaging students in a discussion about lab safety. During the lecture on safety in the chemistry room, ask for a volunteer. Tell students that you have taken a chemical from the stock room that is highly flammable and that you are going to have the volunteer light the chemical on fire. DO NOT tell them the identity of the chemical.
- Before class begins, fill a 100-mL beaker roughly half full with cornstarch. Place in a lab area with the paper, matches, and Bunsen burner.
- After both the instructor and the volunteer student are in appropriate PPE, pour a sample of the corn starch onto a piece of printer paper. A pile with the diameter slightly larger than a quarter is ideal.
- Demonstrate to the students how to appropriately light a match, and then have the volunteer light a match and touch it to the pile of white powder. Remind the students that it is an extremely flammable compound. (The corn starch will not light on fire under these conditions. Act curious as to why it didn’t work and then propose the next idea.)
- Demonstrate to the students the appropriate methodology for lighting a Bunsen burner. Light the Bunsen burner and then have the volunteer light the Bunsen burner by the base and apply the flame to the white powder. Again, warn the class that this is an extremely flammable compound. Be sure that the student is not holding the flame on the paper. (Again the corn starch will not ignite under these conditions.)
- After a moment, have the student put the Bunsen burner back on the lab table. Tell the students that you have an idea. Roll the printer paper (the long way) so that the corn starch is inside of the paper. The diameter of the tube should be between 1 cm and 2 cm.
- Verify that that there is nothing flammable behind the Bunsen burner ESPECIALLY STUDENTS. This is often best done in a fume hood. Point the end of the tube at the flame from the Bunsen burner and blow through the tube ejecting the cornstarch into the flame. A fireball will form during this process. (Practice this step before performing in front of students as distance from the flame and force with which you blow will alter the success of the demo.)
Engage the students in one or all of the following discussion points:
- Following lab procedure is critical because chemicals react in a different manner under different conditions
- Ask questions if something doesn’t seem to be working instead of altering procedure on your own.
- Safety equipment (fire blanket, fire extinguisher and PPE discussion)
- Grain Silo Fires
- Surface area and kinetics