CK-12 Physical Science Concepts - For Middle School

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

• Each element has a unique set of properties that is different from the set of properties of any other element.


• For about 2000 years, people accepted Aristotle’s idea that all matter is made up of just four elements: earth,
  air, water, and fire. Starting about 500 years ago, scientists began discovering all of the elements that are
  known today.


• The smallest particle of an element that still has the properties of that element is the atom. All the atoms of an
  element are like one another, and are different from the atoms of all other elements.

Vocabulary

• atom: Smallest particle of an element that still has the element’s properties.


• element: Pure substance that cannot be separated into any other substances.

Explore More

At the following URL, choose any three elements and learn about their properties, history, and uses. Then create a
table comparing and contrasting the three elements.

http://www.webelements.com/

Review

1. What is an element?


2. Why can an element be identified by its properties?


3. Explain why the following statement is either true or false: The idea that all matter consists of the elements
   was first introduced a few hundred years ago.


4. How are atoms related to elements?