4.1. Evolution of the Atomic Model http://www.ck12.org
4.1 Evolution of the Atomic Model
Lesson Objectives
- Describe the development of the concept of the atom from Democritus to the modern day.
- Compare and contrast the continuous and discontinuous theories of matter.
- State the law of conservation of mass, the law of definite proportions, and the law of multiple proportions.
- Summarize the five essential points of Dalton’s atomic theory.
- Describe the relationship between Dalton’s atomic theory and the law of conservation of mass, the law of
definite proportions, and the law of multiple proportions.
Lesson Vocabulary
- continuous theory of matter: The concept that matter is continuous, infinite, and comes in every form all
around us, and could be divided and subdivided into smaller and smaller pieces without limit. - discontinuous theory of matter: The concept that matter is actually finite and not limitless.
- atom: Fundamental, indivisible particles that make up matter.
- law of definite proportions: States that chemical compounds always contain the same proportion of elements
by mass, regardless of amount. - law of conservation of mass: States that the mass of a reactant must equal the mass of the product for any
chemical process. - law of multiple proportions: States that if two elements form more than one compound between them, then
the ratios of the masses of the second element that combine with a fixed mass of the first element will be ratios
of small whole numbers.
Check Your Understanding
- What are the general properties of matter? For example, what are the properties of water that distinguish it
from other substances? - We widely accept that all matter is comprised of similar kinds of particles that are too small to detect with
the unaided eye. We know that when a candle burns it gives off carbon dioxide and water vapor, but we
cannot actually “see” these gases. How can we study something that we cannot directly see? Can you give an
example?
Introduction
For centuries, humans have been fascinated with the behavior of matter. They have recognized that certain things,
like candles, burn while other things, such as metals, do not readily burn. Humans have noticed that certain
substances react with one another. For instance, iron will rust over time in the presence of air or water. Similarly,