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E2: Describe the evidence that all matter consists of particles called atoms that are made up of certain smaller particles.

Curriculum Organizing Questions	What are the parts of an atom? Draw an atom and its parts. How do we know that atoms exist? How do we know that atoms have parts?
Elaboration	All matter is made of atoms. Until the turn of the 20th C. atoms were thought to be indivisible, but now we know that atoms are made of protons, neutrons, and electrons. Most of the evidence for the existance of atoms was not based on direct observation but was indirect.
Specific Ideas	Scientific ideas about elements were borrowed from some Greek philosophers of 2,000 years earlier, who believed that everything was made from four basic substances: air, earth, fire, and water. It was the combinations of these "elements" in different proportions that gave other substances their observable properties. The Greeks were wrong about those four, but now over 100 different elements have been identified, some rare and some plentiful, out of which everything is made. Because most elements tend to combine with others, few elements are found in their pure form. Benchmarks 4D5 All matter is made up of atoms, which are far too small to see directly through a microscope. The atoms of any element are alike but are different from atoms of other elements. ...Different arrangements of atoms into groups compose all substances. Benchmarks 4D1 Important contributions to the advancment of science and technology have been made by different kinds of people, in different cultures, at different times. Benchmarks 1C1 Until recently, women and racial minorities, because of restriction s on their educational and employment opportunities, were essentailly left out of much of the formal work of the science establishment. Benchmarks 1C2
Developmental & Instructional Implications	Students suusally bring some vocabulary and primitive notions of atomicity to the science class but often lack unerstanding of the evidence and logical arguments that support the particulate model of matter. NSES Standard B p. 149 The structure of matter is difficult for this grade span. Historically, much of the evidence and reasoning used in developing atomic/molecular theory was complicated and abstract. In traditional curricula too, very difficult ideas have been offered to children before most of them had any chance of understanding. Benchmarks p. 77 Possible differences in atoms of the same element should be avoided at this stage. Historically, the identical nature of atoms of the same element was an assumption of atomic theory for a very long time. Benchmarks p. 78 Middle-school and high-school students are deeply committed to a theory of continuous matter (Nussbaum, 1985). Although some students may think that substances can be divided up into small particles, they do not recognize the particles as building blocks, but as formed of basically continuous substances under certain conditions (Pfundt, 1981) Driver p. 96. Much of the details of this indicator seem to be covered more in 9-12 national standards. (Preview Committee)
Examples	How a cyclotron works to make new elements is useful and exciting.

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