Chemistry Chapter 4.1: Early Thoughts About Matter

What two premises formed the basis for Dalton's atomic model?

(1) Combinations of atoms from different elements form compounds. (2) Atoms of different elements have different masses. (Page 79)

The law of definite proportion states that every compound has a definite composition by mass. What does that mean?

According to the law of definite proportion, the masses of the elements in a compound are always in the same ratio, no matter how much of the compound is tested or where the compound comes from. The ratio is unique to that compound. (Page 78)

Compare the types of evidence used by the Greeks and later by John Dalton to support their respective models of the atom.

Dalton's model was based on measured differences in mass and definite composition of compounds. The Greeks relied on philosophical evidence alone. (Page 77-78)

State the law of multiple proportions in your own words.

the law of multiple proportions describes the observation that whenever a fixed amount of an element can combine with different masses of another element, the ratios of the masses of the second element can always be reduced to whole-number ratios. (Page 78)

State the main difference between atomism and the continuous theory of matter.

The continuous theory of matter holds that matter can be divided into infinitely smaller parts. Atomism is the belief that matter exists as discrete particles, that is, atoms, which cannot be further subdivided. (Page 77)

Are the atomic models of Democritus and Dalton directly related? Why or why not?

The two models of the atom are related in their mutual suggestion that matter consists of atoms, but they are the conclusions of two different methods, one philosophical and one scientific. (Page 77-79)