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Hot Popcorn (0 Favorites)

DEMONSTRATION in Heat. Last updated May 24, 2017.


Summary

In this demonstration, the teacher will pop popcorn using three different methods (a hot plate, a microwave, and an air popper) so that the students can experience and investigate three types of heat energy transfer: convection, conduction, and radiation.

Grade Level

Middle School

Objectives

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

  • Compare and contrast the three types of heat transfer: convection, conduction, and radiation.

Chemistry Topics

This demonstration supports students’ understanding of

  • Energy
  • Heat
  • Heat Transfer
  • Convection
  • Radiation
  • Conduction

Time

Teacher Preparation: 30-60 minutes

Lesson: 45-60 minutes

Materials

  • Microwave
  • Air popper
  • Hot plate
  • Small pan and lid
  • Microwave popcorn (1 bag)
  • Popcorn kernels (1 bag)
  • Vegetable oil (1 Tbsp.)
  • 3 small microwave-safe bowls
  • 1-3 electrical outlets
  • Paper bowls for students to eat the popcorn (Optional: if you are going to allow this)
  • 1 stopwatch per student

Safety

  • Students should wear proper safety gear during chemistry demonstrations. Safety goggles and lab apron are required.
  • Exercise caution when using a heat source. Hot plates should be turned off and unplugged as soon as they are no longer needed.

Teacher Notes

  • Background information:
    • The hot plate is the source of conduction heat
    • The microwave is the course of radiation heat
    • The air Popper is the source of convection heat
  • Hints for a successful demo:
    • If you are doing this demonstration in a class period that is 45 minutes-1 hour, I recommend that you have all three devices running at same time. Explain the heat sources to the student to allow enough time for the demo to be completed and the students finish their activities.
    • The students should complete a compare/contrast Venn diagram as a final assessment.
    • Length of class can dictate how quickly the demo must proceed.
    • Allow the students to come up in small groups to view what is occurring up close.
    • The popcorn produced in the radiation and convection demos should be appropriate to share with the students; however the conduction popcorn will be greasy and will not produce a good quality for consuming.
  • Demo procedures:
    • Conduction:
      1. Heat a hot plate and place a pan with lid on the heat source.
      2. Add 1 tablespoon of oil to the pan.
      3. When the pan is heated and the oil is hot, add approximately 15 popcorn kernels and close the lid.
      4. Once the kernels begin to pop, remove the pan from the heat source. Show the class what has occurred.
      5. Optionally, you could do this without the lid and the popcorn will pop out of the pan. However, keep in mind that the oil and popcorn will be very hot.
    • Radiation:
      1. Pop the popcorn in the microwave bag by following the instruction on the box of popcorn.
      2. Be sure to follow the instruction on the box closely so that the popcorn does not burn.
      3. Show the class what has occurred.
    • Convection:
      1. Fill the air popper using the instructions for the popper or fill the inside of the popper to the line with kernels.
      2. Make sure that the lid is in place and a heat resistant bowl is below the opening.
      3. Plug in the unit.
      4. The kernels will be bounced around the inside of the popper by the hot air until they are heated to popping.
      5. Once the kernels are finished popping, show the class what has occurred.

For the Student

Background

There are three types of heat transfer:

  1. Conduction: Conduction occurs when an object that is physically touching a heat source is heated. Example: You touch the metal of a car on a hot summer day. Your hand comes into direct contact with the heat source and your hand feelings a burning sensation.
  2. Convection: Convection occurs when heat from one area moves to a colder area. Example: You drop an ice cube into boiling water. The heat from the boiling water is transferred to the ice cube and the ice cube melts.
  3. Radiation: Radiation takes place in form of electromagnetic waves mainly in the infrared region. Radiation emitted by a body is a consequence of thermal agitation of its composing molecules. Example: You spend too much time out in the sun without a hat or sunscreen. You did not touch the sun but the sun burned you through radiation.

Pre-lab Questions

  1. Give another example of conduction:
  2. Give another example of convection:
  3. Give another example of radiation:

Objective

You will compare/contrast conduction, convection, and radiation.

Safety

  • Students should wear proper safety gear during chemistry demonstrations. Safety goggles and lab apron are required.
  • Exercise caution when using a heat source. Hot plates should be turned off and unplugged as soon as they are no longer needed.

Procedure

Your teacher will demonstrate all three different types of heat transfer. You will complete out the Venn diagram and Analysis section below as the demonstration is given. Your teacher will lead a discussion.

Analysis

For each component of the demo, answer the following questions:

Question

Microwave

Hot Plate

Air Popper

Where was the popcorn when it is popped (container)?

What was the position of the popcorn when it popped?

What kind of sounds did you hear?

On a molecular level, what was happening to the popcorn during the process?

Where was the heat coming from?

What was happening to the popcorn before it popped?

Did the popcorn pop all at once or over time?

How long did it take for the popcorn to pop? Record using a stopwatch.

What kind of heat transfer is this experiment demonstrating?

Conclusion

For your conclusion, consider this question: What is happening to the molecules within the kernel that allows it to expand and become popcorn?