CK-12 Physical Science Concepts - For Middle School

http://www.ck12.org Chapter 2. Matter

MEDIA

Click image to the left for use the URL below.

URL: http://www.ck12.org/flx/render/embeddedobject/54888

Summary

• Around 1800, the English chemist John Dalton reintroduced the idea of the atom, which was first introduced
  by the ancient Greek philosopher named Democritus.


• Dalton did many experiments with gases and compounds that provided evidence for the existence of atoms.


• Dalton developed an atomic theory that is still mostly accepted today. It is one of the most important theories
  in all of science.


• Dalton thought individual atoms were solid, hard spheres, so he modeled them with wooden balls.

Vocabulary

• Dalton’s atomic theory: Theory of John Dalton that all matter consists of indivisible particles called atoms
  that cannot be created or destroyed, that are the same for a given element, and that combine in fixed proportions
  to form compounds.

Explore More

Read the article about Dalton’s atomic theory at the following URL. Then take the online quiz. Be sure to check
your answers and read the explanations for any incorrect answers.

http://antoine.frostburg.edu/chem/senese/101/atoms/dalton.shtml

Review

1. Who was John Dalton?


2. What evidence did Dalton use to argue for the existence of atoms?


3. State Dalton’s atomic theory.


4. Explain how Dalton modeled atoms and compounds.