5-8

E4: Describe how a substance can combine with different substances in different ways depending on the conditions and the properties of each substance.

Curriculum Organizing Questions	How do substances combine? Why do substances combine?
Elaboration	This is a very general indicator, and the Preview Committee suggests applying it to a specific area of study, such as acid-base behavior or combustion.
Specific Ideas	Over 100 different elements have have been identified … out of which everything is made. Benchmark 4D5 becasue most elements tend to combine with others, few elements are found in their pure form. Benchmarks 4D5 Different arrangements of atoms into groups compose all substances. Benchmarks 4D1 Atoms may stick together in well-defined molecules or may be packed together in large arrays. Benchmarks 4D1 An especially important kind of reaction between susbatnces involves combination of oxygen with something else - as in burning or rusting. Benchmarks 4D6
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 Use of sucn terminology as atoms and molecules is premature for these students and can distract from the understanding that can be gained from focusing on the observation and description of macroscopic features of substances and of physical and chemical reactions. At this level, elements and compounds can be defined operationally from their chemical characteristics, but few staudents can understand the idea of atomic and molecular parrticles. NSES Standard B p. 149.
Examples

Back to Big Ideas Grid E

Back to Standard E

Back to Index