Demonstrations, chemical

In this section, multimedia tools refer to computer-based systems that integrate multiple symbol systems (Salomon, 1979), such as text, audio, video, graph, and animation, to demonstrate chemical entities and/or processes at the macro, submicro, or symbolic levels. In the following, we review four multimedia tools—4M Chem, ChemSense, Molecular Workbench, and Connected Chemistry—and use the design principles suggested by Wu and Shah (2004) to summarize how these tools support students in learning chemistry. 

Obviously, use of such databases often fails in case of interaction between additives. As an example we mention additive/antistat interaction in PP, as observed by Dieckmann et al. [166], In this case analysis and performance data demonstrate chemical interaction between glycerol esters and acid neutralisers. This phenomenon is pronounced when the additive is a strong base, like synthetic hydrotalcite, or a metal carboxylate. Similar problems may arise after ageing of a polymer. A common request in a technical support analytical laboratory is to analyse the additives in a sample that has prematurely failed in an exposure test, when at best an unexposed control sample is available. Under some circumstances, heat or light exposure may have transformed the additive into other products. Reaction product identification then usually requires a general library of their spectroscopic or mass spectrometric profiles. For example, Bell et al. [167] have focused attention on the degradation of light stabilisers and antioxidants... 

Dinkelaker B., Hahn G., Romheld V., Wolf G.A, Marschner H. Non-destructive methods for demonstrating chemical changes in the rhizosphere 1. Description of method. Plant Soil 1993 155/156 67-70. 

However chemical methods of mercury detoxification are far from adequate. It has become evident that mercury can be solubilized from HgS under conditions that could be present in a landfill. We have demonstrated chemical solubilization followed by volatilization with Fe2(S04)3, a product of oxidation of FeS04 (pyrite) by Thiobacillus ferrooxidans (data not shown). Other researchers have indicated that T. ferrooxidans can facilitate solubilization and volatilization of Hg° from HgS. Growth of T. ferrooxidans in the presence of cinnabar (mercury ore-contains HgS and some impurities) by Silver and Torma (1984) resulted in dissolved mercury concentration in the bioreactor of 64 mg/L (the form of Hg was not given). In similar experiments with T. ferrooxidans and cinnabar, Baldi and Olson (1987) did not... 

The Effect of SDS Micelle on the Rate of a Reaction, J. Chem. Ed. 1992, 69, 1024 C. P. Palmer, Demonstrating Chemical and Analytical Concepts Using Electrophoresis and Micellar Electrokinetic Chromatography, J. Chem. Ed 1999, 76, 1542. 

Lee R. Summerlin and James L. Ealy, Jr., The Common Ion Effect Second Demonstration," Chemical Demonstrations, A Source-book for Teachers, Vol. 1 (American Chemical Society, Washington, DC, 1988), pp. 93-94. 

In this demonstration, chemical changes occur. With the addition of heat, reactants change into products. New substances are formed with new physical properties. Chemistry is the study of chemical change. 

A schematic diagram of the demonstrator chemical analysis system is given in Fig. 24. The MCB comprises three in/outlets, two micro-pumps, two flow sensors and an optical absorption detector module. The purpose is to measure chemical reaction products by detection of the (spectral) absorption intensity. Sample and reagent liquids are mixed in the appropriate amounts on-board (currently the actual mixing takes place during the propagation in channels) and the optical absorption is measured at the detector side. 

The Lorenz system, partially demonstrating chemical reactions, for creating esthetic patterns... 

We have demonstrated chemical agent detection using accurately binary phase-shaped femtosecond pulses in the laboratory environment. Increase in multidimensionality has shown to improve the reliability of method. Future efforts will be focused on ambient sampling and expansion of database. Graphical user interface of the detection software is shown here (Figure 5) for a set of chemical agent simulants currently in the database. 

If the pinhead reaction demonstrates chemical damage the next point of interest is to determine the exact cause. The tests described below for damage caused by chemicals or fungi are applicable to all cellulosic fibres. 

The presence of phosphomonoesterase in sheaths and mucilaginous material of cyanobacteria has been demonstrated chemically (Weckesser etaL, 1988) and by staining (Grainger et al, 1989). Phosphatases may also be released by cell lysis, but information is sparse about the extent to which such enzymes can become bound to the sheaths or mucilaginous surrounds of living cells of the same or other species. The possible interactions between enzymes external to the cyto-... 

De Vos, W. (1999). Using large glass cylinders to demonstrate chemical reactions. Journal of Chemical Education, 76(4), 528-530. 

Boo (1998) found that only 10% of 48 students from Singapore mentioned Gibbs energy as the driving force of five demonstrated chemical... 

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