Faraday's Candle Chemistry

On the bus this morning I finished reading a copy of Michael Faraday's "The Chemical History of a Candle" based on his famous lecture series over 150 years ago. What an amazing lecturer he was! I had not realized how far back some classic science demos go. My favorite quote:  "We young ones have the perfect right to take toys and make them into philosophy, inasmuch as now-a-days we are turning philosophy into toys." (He was using a suction cup toy to demonstrate air pressure.)  I have not discussed candles much in my lectures, but I have used campfires as examples.

Here is a reference:

Faraday, M.  The Chemical History of a Candle, Sesquicentenary ed., James, F. A. J. L., Ed.; Oxford University Press: Oxford, U.K., 2011.

Geology Demo - Candle Wax Demo

It was noted that when a large candle was placed on a wood stove that the wax in the lower part of candle melted. This melted wax was less dense than the solid, and in some cases rose to the top of the candle and formed flows on the candle surface. This was reminiscent of lava flows in a non-explosive volcanic eruption, so the candle was placed on a small hot plate that could produce more localized heating within the candle. As the pictures show, the melted wax breached the top surface of the candle closest to the center of the hot plate and flowed to the lowest part of the candle surface. When the candle wax cooled and hardened, the remaining liquid wax in the source hole contracted as it became more dense, producing a sort of crater or vent.

BELOW: A candle wax volcano: (LEFT) Liquid wax rising up and almost breaching the top surface of candle. (MIDDLE) The liquid wax "lava" flowing across the candle surface and pooling in a low spot. (RIGHT) When the candle wax cooled and hardened, the remaning liquid wax contracted back into the "vent".

Geology Demo - Snack Layers

To illustrate the Principle of Superposition (oldest rocks are deposited lower than more recent rocks) to a group of Kindergarteners, I poured different types and colors of snack foods into layers into a clear drink pitcher. They seemed to grasp the lowest = oldest connection quite clearly.

Paper Demonstrations

Folded Chiral Paper Structures

Under development. Patterns containing brief instructions on construction and use of these folded paper structures can be downloaded as PDF files from the Internet at: http://bradley.bradley.edu/~campbell/chiralpapersprings.pdf. You are welcome to contact Dean Campbell (http://bradley.bradley.edu/~campbell/campbell@bumail.bradley.edu) to give him feedback on use of this template.

Chemical Cootie Catchers

Patterns containing brief instructions on construction and use of these folded paper structures can be downloaded as PDF files from the Internet at: http://bradley.bradley.edu/~campbell/chemcootiecatchers.html.

 

D. J. Campbell, K. C. Campbell, K. M. Campbell, "Chemical ‘Fortune Tellers’ or ‘Cootie-Catchers’", Chem13 News, March, 2011, 8-9.

Chemical Paper Snowflake Cutouts

 

This paper describes the use of flat paper cutouts with six-fold symmetry for modeling layers of atoms within solid structures. Stacking the cutouts in specific ways illustrates how the layers of the atoms are stacked in the solids. Additionally, these cutouts can be used to demonstrate types of deformation in metals, atomic force microscopy, and carbon nanostructures. These paper lattices can be used on an overhead projector for demonstration to an entire class, or they can be constructed and studied on individual bases by students. K. F. Robinson, P. N. Nguyen, N. Applegren, D. J. Campbell, “Illustrating Close-Packed and Graphite Structures with Paper Snowflake Cutouts” The Chemical Educator, 2007, 12,163-166.

Poisson's Ratio Cutouts Flat, flexible lattices can be used to illustrate Poisson’s ratios of materials. These lattices can be produced from ordinary sheets of paper.
D. J. Campbell, M. K. Querns, "Using Paper Cutouts to Illustrate Poisson's Ratio."  J. Chem. Educ., 2002, 79, 76.

Graphite Cleavage to Graphene Demonstrated with a Deck of Cards

"When a pencil makes a mark on paper, tiny sheets of clay and graphite are rubbed from the pencil “lead” onto the paper fibers.  Recently, scientists have repeatedly split stacked layers of graphite apart (like cutting a deck of cards) to isolate single-atom sheets of graphite.  These single sheets, called graphene, have thicknesses of only a third of a nanometer  – much thinner than the smallest piece of pencil dust." See: http://www.nano.utexas.edu/resources/nano-at-home/.

Chemiluminesent Redox 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.

 

ABOVE: Pretty orange chemiluminescence.

Oxidation of 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.