Demonstration

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• Teacher Guide.pdf
• Teacher Guide.doc
  

Submitted by:
David Dow
Creighton Prep School
Omaha, Nebraska

Thanks to:
Flinn Scientific

Summary

In this demonstration, students observe the combustion of lycopodium powder and discuss the effect of surface area on the reaction rate.

Grade Level

High school

Objectives

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

• explain the relationship between surface area and reaction rate.

Chemistry Topics

This lesson supports students’ understanding of

• Combustion
• Reaction rate
• Ways to change rates

Time

Teacher Preparation: 10 minutes

Lesson: 5 minutes

Materials

• Regular size Pringles can with pencil-size hole near the top
• Squeeze bottle containing lycopodium powder
• Small candle attached to the bottom of a copper wire loop (this allows it to be placed inside the Pringles can)
• Safety goggles
• Safety shield

Safety

• Demonstrator should wear safety goggles and protect students by using a safety shield

Teacher Notes

• Make sure that the explosion occurs a safe distance away from students.

For the Student

Lesson

Engage

1. Discuss how lycopodium powder is similar in flammability to grain dust.
   
   What will happen if a lit match is placed on a small pile of lycopodium powder?

 

2. Make a small pile of lycopodium powder and gently place a lit match on top of it.  It smolders for a while then goes out.

 

Why does this occur?  [only the top part can burn]

What could be done to make the reaction occur faster [provide more surface area]

 

3. Safely use the squeeze bottle to blow lycopodium powder across a lit candle, assuring that no students are close.  A large flame flares.

 

What would happen if this took place in a confined space, such as a grain elevator?

 

4. With the squeeze bottle primed with lycopodium powder, quickly lower the lit candle on the wire into the Pringles can, place the lid on, then squeeze the bulb blowing lycopodium powder inside the can.  It quickly blows the lid off in an explosion.

This was only a small can with a small amount of powder.  Grain elevator explosions can send chunks of concrete some distance and blow out windows blocks away, causing injury and even death.  If the grain elevator had a safety valve, similar to the lid, this could be prevented.

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