Chemistry symbolic representation

If teaching and learning about the submicro is complex, then that about the symbolic is even more so. In Chapter 4, Taber unpicks in detail the ranges of symbolisms used in chemistry the spread of types invoked, those used to represent chemical entities and those used to represent reactions between them. In each case, he analyses the educational problems that they present. He concludes with some broad precepts about how symbolic representations might best be presented in chemical education. 

Nitmerotts examples of chmbing the ladder can be fotmd in textbooks for secondary edncation. For example, textbooks start the stndy of the snbject of salts with the (strb-) microscopic particles of atoms and molectrles, followed by how atoms theoretically ate converted into iotts, and how ionic srrbstances ate brrilt from charged ions. Textbooks continne with the macroscopic properly of the soln-bility of ionic snbstances in water. Snbseqnently mote complex ions, snch as strl-phates and nitrates, ate addressed to become part of the stndents repertoire ns-ing the sub-microscopic world of chemistry and the symbolic representations. For other subjects, such as organic chemistiy, the pathway for stndy from the basic sub-microscopic particles and related chemical principles to making sense of a relevant macro-world of applications (e.g. production of medicines) is very long. Moreover, the sub-microscopic world of state-of-the-art chemistry has become very complex. 

The various symbolic representations used in chemistry can be considered as being part of a specialist language. 

To be able to explain chemical reactions, students will have to develop mental models of the submicroscopic particles of the substances that undergo rearrangement to produce the observed changes. However, students have difficulty in understanding submicroscopic and symbolic representations as these representations are abstract and carmot be directly experienced (Ben-Zvi, Eylon, Silber-stein, 1986, 1988 Griffiths Preston, 1992). As a result, how well students understand chemistry depends on how proficient they are in making sense of the invisible and the untouchable (Kozma Russell, 1997 p. 949). 

Ever since Johnstone (1993) addressed the three levels of chemistry (symbolic, macro, and microscopic, called submicro currently), many studies have investigated how multimedia could support the constraction, development, and evaluation of students mental representations of chemistiy at the three levels. The studies in the previous chapters mention that the representations of the macro-submicro-symbolic relationship play important roles in chemical concept learning. 

Action Research to Promote the Formation of Linkages by Chemistry Stndents Between the Macro, Snbmicro, and Symbolic Representational Levels... 

Hinton, M. E., Nakhleh, M. B. (1999). Students microscopic, macroscopic, and symbolic representations of chemical reactions. Chemistry and Materials Science, 4(5), 158-167. 

Abstract The case is made that, whilst all school-age students should appreciate the nature of and relationship between the macro and submicro types of representation (what we call the Group A Curriculum), only those students intended to study chemistry at an advanced level need to know abont the qnantitative aspects of symbolic representations (what we call the Group B Curriculum). The chapters in this book, together with a framework for effective cnrricnlnm change, are nsed to onthne what needs to be done if a revised education in respect of a representational triplet is to be provided. 

Fig. 5. A symbolic representation according to the Symbolic Synoptic System for Analytical Chemistry (SSSAC) of the complexometric titration of ferric ion in Renn Slag. From H. Malissa and G. Jel-linek, Z. Anal. Chem. 247,3 (1969). Reproduced by permission of Springer Verlag, Berlin.

Fullerenes can encapsulate various atoms within the cages, and these compounds have been referred to as endohedral fullerenes. For example, the symbolic representations La C6o and La2 Cso indicate that the fullerene cage encapsulates one and two lanthanum atom(s), respectively. The IUPAC description refers to these fullerenes species as incar-fullerenes, and the formulas are written as t LaCeo and tl Cso, (i is derived from incarcerane). Some metal endohedral fullerenes are listed in Table 14.2.1. The endohedral fullerenes are expected to have interesting and potentially very useful bulk properties as well as a fascinating chemistry. Some non-metallic elements, such as N, P, and noble gases, can be incarcerated into fullerenes to form N 0,0, P C6o, N C o, Sc3N C80, Ar Oo, etc. 

Many areas of chemistry need some notation for the capture of mathematical expressions and complex symbols. Representation of mathematics is very complex, and we strongly advise against individual development of these languages. Fortunately, there exists a mathematical XML language MathML, by the W3C (Carlisle et al. 

There is another important symbol that is used in chemistry that will help you to recognize solutions. When a substance such as salt is dissolved in water, its chemical formula will be followed by the subscript (aq), which stands for aqueous. An aqueous substance is one that is dissolved in water (in other words, a solution). You need to get in the habit of paying attention to the symbols, so that you can differentiate between the symbolic representations of substances. 

Wilhamson VM, Abraham MR (1995) The effects of computer animation on the particulate mental models of college chemistry students. J Res Sci Teach 32 521-534 Russel JW, Kozma RB, Jones T, Wykoff J, Marx N, Davis J (1997) Use of simultaneous, synchronized macroscopic, microscopic and symbolic representations to enhance the teaching and learning of chemical concepts. J Chem Educ 74 330-334... 

In the cryptic expression and symbolic representation which characterised alchemy and found a later expression in the symbols and formulae of modern chemistry, sophic sulphur and sophic mercury assumed a bewildering variety of forms. For example, they were known as Osiris and Isis, sun and moon, Sol and Luna, brother and sister, masculine and feminine, active and passive, giver and receiver, seal and wax, fixed and volatile, wingless lion and winged lioness, lion and eagle, and so forth. The Stone, when conceived as the result of the union of masculine and feminine principles, was sometimes represented as an infant. 

Besides his table of atomic masses, Berzelius made many other major contributions to chemistry. The most important of these was the invention of a simple set of symbols for the elements along with a system for writing the formulas of compounds to replace the awkward symbolic representations of the alchemists. Although some chemists, including Dalton, objected to the new system, it was gradually adopted and forms the basis of the system we use today. 

An additional problem is that in chemistry we are concerned with the forging of links between specific types of narratives, situations, and the chemical substances that contribute to their explanation. The latter can be progressively considered at the macro level (e.g. as the white solid commonly called salt and, in its chemical context, sodium chloride ), at the sub-micro level (e.g. as a lattice of sodium and chloride ions), and at the corresponding symbolic representational level (e.g. (Na " Cl )s)- The depth of the understanding acquired will be related to the level of the explanation reached. 

Chemical bonding is a key concept in chemistry. It is also a topic area where understanding is developed through diverse models - which are in turn built upon a range of physical principles - and where learners are expected to interpret a disparate range of symbolic representations standing for chemical bonds. 

Russell et al. (17) used a repeated measures /-test to determine the effectiveness of animations showing synchronous depictions of chemical reactions using the macroscopic, microscopic, and symbolic representations on students conceptual chemistry knowledge. Students in two sections of college introductory chemistry were given a pre-test, then received instruction using these animations, and answered similar questions on a post-test. A comparison of pre- and post-test scores (presumably done using difference scores) showed a... 

A central feature of the way chemistry is presented and discussed in classrooms is the set of representations (such as formulae and chemical equations) used. This is often seen as a third level distinct from the molar and submicroscopic levels, but is more helpfully understood as a specialised language that allows us to shift between those two levels (see Chapter 3). Translating between observable phenomena, symbolic representations and theoretical models is a key part both of teaching, and learning, chemistry. 

The third way that chemists perceive their subject is to use symbols to represent the atoms, molecules, and reactions that make up the science. We will wait to introduce this perspective in detail in the next two chapters—but here we point out that you certainly have encountered chemical symbols in your previous studies. The famous H two O molecule we have noted is never depicted as we have done here in the quotation marks. Rather, you have seen the symbolic representation of water, H2O. In Chapter 2, we will look at chemical formulas in more detail and in Chapter 3, we will see how we use them to describe reactions using chemical equations. For now, we simply note that this symbolic level of understanding is very important because it provides a way to discuss some of the most abstract parts of chemistry. We need to think about atoms and molecules, and the symbolic representation provides a convenient way to keep track of these particles we ll never acmally see. These symbols will be one of the key ways that we interact with ideas at the particulate level. 

The inteiiectuai power of chemistry often iies in the way it aiiows us to iook at a probiem (or a design) from a number of perspectives. Both the physicai and chemicai properties of substances can be considered at the macroscopic or microscopic (particuiate) ievei depending on the nature of the question or probiem being considered. In addition, we often need to use symbolic representations to designate what is happening in chemical systems, so ultimately there are three perspectives that we will find useful throughout this text. 

Symbolic perspective (1.2) Viewpoint of chemistry focusing on symbolic representations of the substances involved through formulas, equations, etc. 

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