Scientific Models

1
Scientific Models

• Observation and Assumption

2

• Observation
• Direct counting with a Geiger Counter and
  formation of elements in radioactive decomposition

• Assumption
• Elements consist of discrete particles of atoms

3

• Observation
• Atoms cannot be seen with a high-powered
  microscope

• Assumption
• Atoms must be very small and therefore must be
  very numerous

4

• Observation
• Elements have characteristic properties

• Assumption
• All atoms of the same element are identical.
  Atoms of different elements are different from
  each other.

5

• Observation
• Elements form compounds that have their own
  characteristic properties

• Assumption
• Atoms combine to form special patterns that are
  different from mere mixtures of atoms.
• The number of atoms does not change, nor does
  their mass.

6

• Observation
• Elements and compounds are substantially less
  dense as gases than as liquids. Gases are easily
  compressible solids and liquids are not.

• Assumption
• Atoms behave like small, hard objects. The size
  and mass of atoms remains fixed. In a gas, they
  are far apart. In a solid, they touch each
  other.

7

• Observation
• Analysis of many compounds, including observation
  of the properties of gaseous compounds

• Assumption
• Molecular formulas

8

• Observation
• In radioactive decay, one element changes into
  two other elements.

• Assumption
• Atoms of a radioactive element disintegrate into
  atoms of other elements.