Michael Faraday (1791-1867). Michael Faraday was one of ten children of a London blacksmith and his wife. He had little formal education and was originally apprenticed to a bookbinder when he was 14 years old. Faraday taught himself to read in the bookbinder's shop and first learned about electricity, which was just being discovered during his teenage years, from an article in an encyclopedia brought to his employer for rebinding. Because electrical phenomena piqued his interest, he joined a group in London who attended lectures on science. He wrote complete notes on lectures he heard and had them bound in a book.
In 1812, he attended lectures given by Humphry Davy at the Royal Institution. He was so interested in Davy's talk that he applied to Davy, the institute director, for a job as his assistant. He finally obtained the position after following the advice of friends and sending his bound notes to Davy. This marked the start of Faraday's illustrious scientific career and his prolific collaboration with Davy. He went on to become the principal lecturer at the Institution and did much to popularize science among the British upper class; his Christmas lectures on the chemistry of candles remains a classic. In 1825, he replaced Davy as director of the Institution and his reputation soon began to rival that of Davy.
Faraday's work in analytical chemistry resulted in the discovery of benzene and many compounds of chlorine and carbon. He was the first to liquefy several gases, including CO2 , H2S, HBr, and Cl2 . However, he is most famous for his work with electricity and electrochemistry. He discovered the principles that underlie modern electrical generators when he observed that a current is induced in a coil of wire rotating in a magnetic field. His experimental and theoretical work in electricity and magnetism formed the basis of later developments by James Clerk Maxwell. Albert Einstein rated Faraday along with Newton, Galileo, and Maxwell as one of the greatest physicists of all time. Faraday went on to prove that electricity generated in a magnetic field was identical to electricity produced by an electrochemical cell and performed many experiments measuring changes taking place in electrochemical cells. His work established two laws of electrochemistry still named after him in chemistry books: (1) The amount of material deposited in an electrochemical cell is proportional to the current passing through it, and (2) the amounts of substances deposited and/or dissolved in electrochemical cells are proportional to their molar masses.
A man of strong religious beliefs, Faraday tried to live a simple life, accepting rather reluctantly the many honors that came to him. His beliefs allowed him to solve without uncertainty a moral problem that still faces scientists. During the Crimean War between England and Russia in the 1850s, the British government asked him to head an investigation of the possibility of preparing large quantities of poison gas for battlefield use. Faraday refused to consider the idea, and nothing came of it at that time. Poisonous gas was eventually used in warfare during World War I in the early part of the 20th century.
Charles Hall (1863 - 1914) and Paul Heroult (1863 - 1914). The process used today for aluminum metal manufacture was invented independently at almost the same time by a young Frenchman, Paul Heroult, and a young American, Charles Hall. Hall invented the process while he was still an undergraduate at Oberlin College. He was inspired by a professor's remark that anyone inventing a cheap process for mass-producing aluminum would make a fortune. After graduation, Hall set up a laboratory in a woodshed--the 19th century equivalent to a garage--using homemade and borrowed equipment. After a year, he found that cryolite, Na3 AlF6 , would dissolve alumina (aluminum oxide) to give a conducting solution from which aluminum could be deposited by electrolysis. He used an iron frying pan as a container for the cryolite-alumina mixture, which he melted over a blacksmith's forge. The electric current came from electrochemical cells he made from jars used for canning fruit. (See the Gerber Cell demonstration described in this module.) As a result of the discovery made by Hall and Heroult, large-scale production of aluminum became economically feasible for the first time, and it became a common and familiar metal. Hall and Heroult share an interesting history. They were born in the same year, they discovered aluminum independently of each other in the same year, and they died in the same year.
1. Message on a T-shirt: I've got potential--Let's realize it!
2. "The patriotic ion went to the pole and volted." (CHEM 13 NEWS, September 1980, p. 13)
3. Word Search (see Appendix for master copy)
Words about the concepts in this module can be obtained from the clues given. Find these words in the block of letters:
1. Driving force in a voltaic cell. (2 words)
2. Either of two parts of an oxidation-reduction reaction. (2 words)
3. Electrical quantity measured in amperes.
4. Unit of electrical potential.
5. Electrode at which reduction occurs.
6. Negative ion.
7. Type of cell where chemical energy is converted to electrical energy spontaneously by a redox reaction
8. Process by which metals are oxidized in the atmosphere
9. State in which NaCl must be in order to conduct electricity
10. Device containing an electrolyte that connects the two compartments of a voltaic cell. (2 words)
Answers: 1. CELL POTENTIAL 2. HALF REACTION 3. CURRENT 4. VOLT 5. CATHODE 6. ANION 7. GALVANIC 8. CORROSION 9. MOLTEN 10. SALT BRIDGE
4. Electrochemistry Crossword Puzzle (see Appendix)
5. See cartoons at end of module.
1. The World of Chemistry videotape "Number 15: The Busy Electron," can be used by chemistry teachers at all levels. World of Chemistry Videocassettes. Annenberg/CPB Project, P.O. Box 1922, Santa Barbara, CA 93116-1922; (800) 532-7637; World of Chemistry Series, Atlantic Video, 150 South Gordon Street, Alexandria, VA 22304; (703) 823-2800 or QUEUE Educational Video, 338 Commerce Drive, Fairfield, CT 06430; (800) 232-2224.
2. Electrical Interactions in Chemistry is a film/video available from Ward's Natural Science Establishment, Inc., P.O. Box 92912, Rochester, NY 14692- 9012; (800) 962-2660.
3. Doing Chemistry, videodisc set available from the American Chemical Society, 1155-16th St., N.W., Washington, DC 20036; (202) 872-4382.
This three-disc set contains large numbers of laboratory and demonstration activities presented both as motion and still shots. It can be supported with Macintosh computer programs that provide access to HyperCard stacks for lesson planning and handout preparation, and that enable teachers to create their own videotapes. Over 700 pages of print materials are also available. In addition to the other fine activities, it includes two pertaining directly to electrochemistry: "DEMO E30: Daniell Cell;" and "DEMO E31: Galvanic Cell Based on Aluminum Oxidation."
4. Software published by Project SERAPHIM, Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue. Madison, Wl 53706-1396: (608) 263-2837 (voice) or (608) 262-0381 (FAX).
a. For the Apple II computer: AP 603 (includes Faraday 2, a simulation of Faraday's Laws in a laboratory experiment and Faraday Aid, a data analysis program used in conjunction with Faraday 2)
b. For IBM PCs and PC-compatibles: PC 3101 (Faraday 2 and Faraday Aid)
5. Videodisc published by JCE: Software, a publication of the Journal of Chemical Education, Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue. Madison, Wl 53706-1396: (608) 262-5153 (voice) or (608) 262-0381 (FAX).
"Copper-Zinc Electrochemical Cell," a chapter on The World of Chemistry: Selected Demonstrations and Animations: Disc I (double sided, 60 min.), Special Issue 3.
6. Software published by JCE: Software, a publication of the Journal of Chemical Education, Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue. Madison, Wl 53706-1396: (608) 262-5153 (voice) or (608) 262-0381 (FAX).
Frost Diagrams, by James P. Birk and Heidi Hocker. Vol. IV C, No. 1, for the Apple Macintosh.
1. Power Supplies for Electrolysis. Try using AC adapters used for tape recorders or transistor radios. They are rated for different electric potentials and currents, depending on their applications. 9-V, 500-milliampere adaptors commonly available at Radio Shack stores work well for most applications. Also, 9-V radio batteries will drive most aqueous electrolysis processes of interest in first-year chemistry courses.
2. Supporting Electrolytes. Sodium sulfate, potassium nitrate, and sodium nitrate are all good, unreactive electrolytes to use in electrochemical cells. Chloride salts will react with any silver cations formed, and will also undergo oxidation to chlorine gas at the anode of electrolytic cells.
3. Salt Bridges. Salt bridges can be made with a variety of methods and materials. See the laboratory activity section of this module for instructions on making agar salt bridges. A cotton string or piece of filter paper soaked with an electrolyte solution will work as long as it remains wet.
4. Voltmeters. If you attempt to measure the potential of a voltaic cell directly with a voltmeter, be sure to use a meter with high impedance. Many inexpensive meters, especially those sold in science education supply catalogs, are low impedance and draw too much current from the cell to accurately determine the cell potential. Radio Shack, Sears, and others market relatively inexpensive multimeters of high impedance that can also measure current and resistance.
5. Inert Electrodes. Platinum wire makes excellent inert electrodes. However, it is very expensive. A recipe for preparing platinum electrodes is provided under Instrumentation. Graphite pencil "leads" also work well, although they sometimes offer too much resistance if the pencil lead diameter is too small. Thick pencils used by young children and thick square pencils used by artists are easier to handle. Just carve the wood away from the graphite at both ends. Paint on the pencil wood can be removed by sanding. Old dry cell batteries usually contain carbon electrodes as well. Because they are much thicker than pencil leads, they do not break as easily and offer much less resistance. To obtain them, dissect old batteries. (NOTE: Avoid alkaline, lithium, NiCad, mercury, and other such batteries.) The carbon electrodes in the center can be cleaned with any strong oxidizer that has a lower reduction potential than manganese dioxide/permanganate half-reaction. The electrodes can also be sanded clean.
Measuring the electric potential at which oxidation or reduction occurs under varying sets of conditions comprises a major subset of chemical instrumentation. You and your students can make simple electrochemical instruments for your laboratory. Directions for one such instrument are found in Extensions and Projects. Building any such instrument and making it work constitutes an excellent student project. The literature is full of references for building instruments. Specifically, look in old issues of the Journal of Chemical Education, "The Amateur Scientist" column in Scientific American when it was written by C. L. Strong, and American Journal of Physics. The electronics in those old instrument recipes are specified for vacuum tubes. These tubes can be duplicated by modern transistors and operational amplifiers. Find a ham radio operator, electrical engineer, electronic technician, or physics teacher to help you choose substitute parts. Instrument recipes as well as many other tips can be obtained at many science teacher meetings and conventions.
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