CK-12 Physical Science Concepts - For Middle School

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

Summary

• Around 400 B.C.E., the Greek philosopher Democritus introduced the idea of the atom as the basic building
  block matter.


• Democritus thought that atoms are tiny, uncuttable, solid particles that are surrounded by empty space and
  constantly moving at random.


• Democritus surmised that different kinds of matter consist of different types or arrangements of atoms.

Explore More

Watch the video at the following URL, and then develop a hypothesis to explain the results of the two experiments.
Relate your hypothesis to Democritus’ ideas about atoms.

http://www.youtube.com/watch?v=g7debF-bSj8 (3:32)

MEDIA

Click image to the left for use the URL below.

URL: http://www.ck12.org/flx/render/embeddedobject/54895

Review

1. Who was Democritus?


2. How did Democritus reason for the existence of atoms?


3. How did Democritus describe atoms?


4. Discuss how well Democritus’ ideas about atoms have withstood the test of time.


5. Iron and lead are both metals, but iron is much harder than lead. How do you think Democritus might have
   explained this difference?