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Name:   Marie H.
Status:   educator
Age: N/A
Location: N/A
Country: N/A
Date: 2000


Question:
What simple, safe compounds might I have students (11-12 year olds) combine to observe a "dramatic or flashy" chemical reaction other than with materials such as salt, vinegar, baking soda, etc? I have 38 students in a lab and am stuck on issues such as safety and lack of chemicals. Any suggestions? We have just finished elements and are moving toward compounds and chemical reactions. Any ideas on flame testing that I could do as demo for large group? SOS please.


Replies:
Marie,

Assuming you have access to a Bunsen burner ...

Find someone who has an ordinary bench grinder that he/she uses to sharpen chisels, drills, mower blades and the like. Collect the steel filings that are near the grinding wheel -- or just purchase some very fine iron filings from a scientific supply house.

Light the burner and then (from about a foot above) sprinkle the filings sparingly in the flame. You will see a very pretty shower of sparks as the iron burns and becomes iron oxide. The finer the filings, the prettier the show. You can then explain to the students that fireworks sparklers contain metal filings the burn to form all those pretty sparks.

The oxidation process occurring in the flame is much the same as that which occurs when steel (mostly iron) rusts -- except "rusting" takes a lot longer for the process to be completed. The flame simply hurries the oxidation reaction to completion.

Next, wrap a magnet in a paper towel* and demonstrate that before the steel filings are sprinkled in the flame, they are attracted to a magnet. Once burned to iron oxide, the material is no longer attracted to the magnet. You can prove this by attempting to pick up the material that has fallen through the flame onto the desktop. Particles that are attracted to the magnet are unreacted metal. You will discover some particles that are not attracted -- those are iron oxide.

* Why the paper towel? To keep the magnet clean and free of steel whiskers that are difficult to pick off.

Regards,
ProfHoff



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