8. Students could perform quantitative experiments using enzymes (biological catalysts) such as catalase (available as a powder) and the enzymes contained in yeast cells. Variables to be tested include temperature, concentration and pH. There are ways to quantify the rates of the chemical reaction through the measure of gas production (carbon dioxide). Check with your biology colleagues for some lab procedures that involve floating disks. (see ) Anticipating Student Questions 1. “Compared with metals, why does a non-metal compound not conduct electricity or possess magnetic properties?” Non-metal compounds involve bonding that does not provide for valence electrons that are easily displaced for conduction. Metals have bonding (non-directional) that involves valence electrons that are not as tightly bonded and are easier to displace for conduction (an array of metal cations in a “sea” of electrons). Magnetic properties are dependent on unpaired electrons that are influenced by the orientation of neighboring electrons. In the presence of a magnetic field, the electrons align strongly in the same direction creating a magnetic force in the metal. 2. “How does an alloy differ from an amalgam?” An alloy is a mix of metals (more than one element)—there are solution alloys, heterogeneous alloys and inter-metallic alloys. An amalgam is a special case of an alloy in which mercury is present as a solvent. 3. “Is an ore a rock or a piece of metal ready to melt?” An ore is rock material that contains minerals that are metal-containing compounds from which a metal can be extracted using various procedures including heat and electricity. 4. “Can a solar cell use light sources other than sunlight?” As long as the light source provides frequencies of electromagnetic radiation to which a solar cell is capable of responding, the energy will be absorbed. The light does not have to be sunlight. 65
References As mentioned, there is a book as well as a video series on the history of developing and using metals in cultures (“the impact of metals on the history of mankind”). The book, “ Out of the Fiery Furnace” by Robert Raymond is available from The Pennsylvania State University Press, 1984, ISBN 0-271-0041-X (pbk). The video series can be obtained from the Univ. of California ( ) . Web Sites for Additional Information More sites on solar cells (explains the basics of how a solar cell works) - cells (use of thin film to improve transmission/absorption of light) (use of molten salts to store the heat generated by solar absorption during the day, then use the heat to convert water to steam to power electricity-generating turbines at night)
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