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Metallic Bonding & Magnetics (6 Favorites)

DEMONSTRATION in Electricity, Electrostatic Forces, Metallic Bonding, Electrons. Last updated July 17, 2017.


Summary

In this demonstration students will observe how electrons flow through a metal in an example of metallic bonding. Using tubes made of different metal materials as well as one made of plastic, in combination with a rare earth magnet (neodymium magnet) the teacher will demonstrate how electrons will flow freely through a metal and create a magnetic field.

Grade Level

High School

Objectives

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

  • Visualize the “free-moving electrons” in metallic bonding.
  • Understand a magnetic field.
  • Realize that an electric current can be induced by a magnetic field.
  • Identify that different metals have different properties.

Chemistry Topics

This demonstration supports students’ understanding of

  • Metallic bonding
  • Magnetism
  • Electric current
  • Electrons
  • Lenz’s Law
  • Metals

Time

Teacher Preparation: 5 - 10 minutes

Lesson: 30 -50 minutes

Materials

  • Rare earth magnets (also called: neodymium magnets)
  • 30 cm Copper pipe, or longer (similar diameter to the magnet; the magnet should fit in the pipe with a little room to move)
  • 30 cm Aluminum pipe , or longer
  • 30 cm Steel pipe, or longer
  • Plastic pipe (PVC)
  • Piece of steel (same size as magnet)

Safety

  • Neodymium magnets are surprisingly powerful when they snap towards metal or another magnet. Be careful when using them, and be especially cautious with your fingers.
  • Don’t allow students to play with magnets in a way that could cause them harm.
  • Never place a pipe that has a magnet in it in your mouth. These magnets should not be ingested.
  • The magnets are very brittle. Don’t let them fall on to hard surfaces (such as concrete) as they can easily shatter into very sharp pieces.
  • These magnets are very strong and they can easily demagnetize items. Be careful where you store the magnets and attentive to what objects are placed near them.
  • Students should wear proper safety gear during chemistry demonstrations. Safety goggles and lab apron are required.

Teacher Notes

  • All of the materials can be purchased at any hardware store or online through sites such as Amazon.
  • This website explains background information about Lenz’s Law and how it applies to dropping a rare earth magnet down a copper pipe. It has a good video showing how the magnetic field slows the movement of the magnet as well.
  • Magnetism Resources:
  • I suggesting starting this demonstration with a control experiment. You can do this by either dropping steel down the copper pipe or a rare magnet down a plastic pipe. This would provide a result that the students would predict: the object will fall at the speed of gravity as expected.
  • Next, I would show that the magnet isn’t magnetically attracted to the copper pipe; explaining that copper isn’t magnetic like a refrigerator, and that the magnet will fall much slower than the students expect.
  • Depending on how much time you have or how deep into the topic you want to go you can demonstrate what happens to the magnet in different pipes (copper, aluminum, steel (iron), etc.) and do comparisons, recording time, and/or discuss the atomic structures of the metals.
  • You can also extend this lesson further by using a magnet to move food items like grapes. There is good information about here: Magnetic Fruit

For the Student

Background

Metallic bonds are found only in metals. Freely moving valence electrons are attracted to the positive metal ions. This creates a “sea of electrons” which gives these materials their unique properties. Metallic bonds are in metallic solids with very high melting points that are not water soluble. They are excellent conductors of electricity and tend to be malleable, lustrous, and ductile.

Safety

  • Neodymium magnets are surprisingly powerful when they snap towards metal or another magnet. Be careful when using them, and be especially cautious with your fingers.
  • Never place a pipe that has a magnet in it in your mouth. These magnets should not be ingested.
  • The magnets are very brittle. Don’t let them fall on to hard surfaces (such as concrete) as they can easily shatter into very sharp pieces.
  • Students should wear proper safety gear during chemistry demonstrations. Safety goggles and lab apron are required.

Analysis

  1. What happens when the magnet is dropped into the plastic pipe? (What forces are in play?)
  2. What happens when the magnet is dropped into the copper pipe? Is this the result you expected?
  3. What forces do you think are interacting with the copper and the magnet?
  4. What changes, if anything, when a different pipe is used?
  5. How can you explain the differences, or similarities, between all of the different pipe materials?
  6. How would you use your observations of this demonstration to explain how electricity works?
  7. Based on your observations, why do you think copper is the most common metal used in power lines?