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!
This unit defines matter and describes its properties. It compares elements, compounds, and mixtures. It explains how matter changes state and identifies special properties of gases. The unit also delves into atoms and elements, including how elements are classified.