Demonstrations Page 7 - Redox

Scroll down to view photographs and short descriptions of some of the demonstrations in the list below.

WARNING – Use at your own risk! We cannot guarantee the accuracy or the safety of these activities.  Some of these activities are far more dangerous than others. The contributors and Bradley University do not assume any responsibility for these activities or their results.  If you have questions, corrections, or comments please do not hesitate to contact Dean Campbell ( at Bradley University.

Ferrofluid Demonstrations
Refrigerator Magnet Demonstrations
Polydimethysiloxane Demonstrations
LEGO® Brick Chemistry and Nanotechnology Demonstrations

Vitamin C Cleans Up Iodine Stains on Hand

I learned this demo from a visitor to campus a couple years ago. This demo takes only a couple minutes. To put this together, you need to go to the local drugstore/grocery store and pick up the following:
-iodine solution (tincture of iodine, used as a disinfectant)
-spray starch
-vitamin C tablets
Step 1 - Smear some of the iodine solution on the palm of your hand. DO NOT let the iodine solution dry out (otherwise it will be hard to remove).
Step 2 - While the iodine solution is still wet, spray some starch onto the palm of your hand. The iodine spot turns blue-black as the starch molecules wrap around the iodine molecules. Again, DO NOT let this mess on your hand dry out.
Step 3 - While the iodine/starch solution is still wet, take a vitamin C tablet and rub it across the stain (I make a smiley face first). The dark stain disappears though sometimes there might still be some yellow tint left. The vitamin C tablet acts as an antioxidant, reducing the iodine to iodide ions and breaking apart the starch/iodine complex. The tablet itself stays fairly white, this it not simply rubbing the stain off, it is a chemical reaction.
Wash your hands with soap and water as soon as you get the chance after the demo (the starch on your hand will still be sticky/slimy).
Iodine stains all sorts of things, so do not spill it.
DO NOT eat the vitamin C tablet that you used in the demo, though you should be able to use the same tablet multiple times.
You should try this demo by yourself first in case I missed any subtle details.
VARIATION: A counterfeit money marking pen, which apparently contains iodine, can be used instead of tincture of iodine. The iodine in the pen does not react with the cloth fibers in real money, but it does react with the cellulose fibers in counterfeit money. The pen can be used to draw light tinted patterns on skin, but the markings dry out fairly quickly so the starch must be applied quickly to turn them dark. These starch/iodine marks can also be erased with a vitamin C tablet.
ABOVE: (LEFT) Step 1 (MIDDLE) Step 3 and (RIGHT) Variation: Erasing counterfeit money pen marks.
Coin Batteries
These batteries are simply voltaic piles made by stacking alternating types of coins with filter paper soaked in saturated salt water solution. The metal compositions of pennies are sufficiently different from nickels so that these coins may be used to make weak batteries. More coins can produce more voltage, but there is a tremendous variability in the actual voltage measured. This is likely due to effects such as internal resistance and degree of corrosion on the coins.
See: Scharlin, P.; Battino, R.; Boschman, E. J. Chem. Educ. 1991, 68, 665.
ABOVE: (LEFT) A simple coin battery - a nickel on salt-water soaked filter paper on a penny. (MIDDLE) Measuring the potential of a single pair of coins (in millivolts). (RIGHT) Measuring the potential of multiple pairs of coins (in millivolts).
Iron Filings in a Sealed Bottle
A couple of years ago I placed coarse iron powder in a sealed bottle to use in magnetism demonstrations. Recently I noticed that the bottle had partially collapsed and hypothesized that it the oxygen in the bottle's air had oxidized the iron to produce iron oxide. I used the volume displacement method (a large graduated cylinder partially filled with water) to estimate the gas volume in the collapsed bottle (405 mL) and in the bottle after allowing air to refill the bottle (490 mL). This represents a percent gas volume change of 17%, which is in the ballpark of the typical 21% oxygen concentration for air.
See: Campbell, D. J.; Bannon, S. J.; Gunter, M. M. J. Chem. Educ., 2011, 88, 784-785.
ABOVE: (LEFT) Partially collapsed bottle containing iron powder. (RIGHT) Reinflated bottle containing iron powder.
Chemiluminesent Reaction
This reaction involves a water/acetonitrile solvent, tris(bipyridine)ruthenium(II) ions, ammonium persulfate, and magnesium metal. During the course of the electron transfers in this system, the excited ruthenium complex emits an orange glow near the magnesium metal, producing the appearance of hot coals in the bottom of the reaction vial.
See: White, H. S.; Bard, A. J. J. Am. Chem. Soc., 1982, 104, 6891.
chemiluminescent reaction
ABOVE: Pretty orange chemiluminescence.
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Last updated 2/14/12

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