5-8

E6: Explain how the relatively small number of naturally occuring elements can result in the large variety of substances found in the world.

Curriculum Organizing Questions	Of what elements are this substance made? What different substancs can be made from this element? How are these substances' properties different?
Elaboration	Students should see a great many examples of reactions between substances that produce new substances very different from the reactants. Then they can begin to absorb the rudiments of atomic/molecular theory, being helped to see that the value of the notion of atoms lies in the explanations it provides for a wide variety of behavior of matter. Benchmarks p. 78 This is strongly conected to E4 and E7 - see those indicators for more details.
Specific Ideas	Over 100 different elements have been identified, some rare and some plentiful, out of which everything is made. Benchmarks 4D5 Substances react chemically in characteristic ways with other substances to form new substances with different characteristic properties. NSES B1b Substances are often placed in categories or groups if they react in similar ways: ex. metals. NSES B1b
Developmental & Instructional Implications	In general, pupils find difficulty in developing an adequete conception of the chemical combination of elements until they can interpret combination at the particle level. However, a particulate view does not ensure an understanding of chemical combination. Driver p. 97 At this level, elements and compounds can be defined operationally from their chemical characteristics, but few students can comprehend the idea of atomic and molecular particles. NSES Standard B p. 149.
Examples

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