Materials
Iron filings or shavings
Bar magnets
Horseshoe magnets
Round magnets (speaker magnets work well)
Paper clips
String
Scientific method worksheet (below)
Paper and pencil
Baby food jars 3/4 full of vegetable oil
Items to test for magnetic attraction (coins, nails, plastic, styrofoam, wood, cloth, paper clips, etc.)

Procedure

Eye opener!
Begin the experiment on magnetism with a quick and easy attention-getter.  First, tape a strong magnet to the bottom of a box.  Second, tie a string to a paper clip that is just long enough to reach from the floor to the tabletop.  Then, tape the string to the floor, pull the box so that the magnet is leaning off the edge of the table, and VOILA! A levitating paper clip.  Once you have the kids' attention, ask a few questions.  For example, how do magnets work?  Does it matter if you put a sheet of paper between the magnet and the paper clip?  What about a pencil?  What about a piece of metal?

What can a magnet pick up?
Have the students fill out the scientific method worksheet.  Then, using different magnets, have each group test the items to see what the magnet will pick up.  Compare the results to the hypothesis sheet and see how closely they actually match.  For the groups that finish early, have them try and figure out how many paper clips they can pick up with each magnet.  Can the magnet pick up a second paper clip while only touching the first?  Why is that?

What does a magnetic field look like?
This experiment really amazes the students.  Begin by giving each group some iron filings.  Have the group take the bar magnet and lay a piece of paper over it.  Then slowly have each group sprinkle iron filings over the sheet of paper.  The magnetic field begins to show in two dimensions.  Repeat with the horseshoe and round magnets.  Do the fields look the same?  Have the groups draw what each of the magnetic fields looks like.  To see the results in three dimensions, add the iron filings to the baby food jars filled with oil.  Seal well and give a shake.  When the magnets are placed near the jar, the iron filings will move suspended in the oil in the shape of the field.  For this to work properly, you need a strong magnet.

WORKSHEET

The Scientific Method

Problem
What is the problem that you are observing?

Hypothesis
How do you propose that this problem be solved?

Test
Perform the test using the hypothesis that was designed.

Results
How well did your hypothesis work?  If it wasn't successful, think of another hypothesis and repeat the test.

Shawn Len, 2000.

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