http://www.ck12.org Chapter 2. Matter
Introduction
What do think this picture shows? Here’s a hint: This illustration mimics a photo taken with a special microscope
that makes images of things that are extremely small. In fact, the gray spheres in the image represent things so small
that trillions of them would fit inside the period at the end of this sentence. Each gray sphere is an atom of lead.
Do you know what atoms are? They are the basic building blocks of matter. Matter, in turn, is all the “stuff” in the
universe. In this unit you will learn much more about matter—from things as simple as atoms to as complex as you!