http://www.ck12.org Chapter 2. Matter and Change
2.2 Classification of Matter
Lesson Objectives
- Define a mixture and understand why mixtures are different than pure substances.
- Classify mixtures as homogeneous or heterogeneous.
- Describe several ways to separate mixtures.
- Distinguish between elements and compounds.
Lesson Vocabulary
- chemical change
- chemical formula
- chemical symbol
- compound
- distillation
- element
- filtration
- heterogeneous mixture
- homogeneous mixture
- mixture
- phase
Check Your Understanding
Recalling Prior Knowledge
- What is a pure substance?
- What are some examples of physical changes, and what happens to the identity of a substance when it
undergoes a physical change?
In the previous lesson, “Properties of Matter,” we learned about the physical properties of pure substances and about
the physical changes that matter can undergo. However, there are many examples of matter that cannot be classified
as pure substances because they have a composition that is variable rather than fixed.
Mixtures
Ordinary table salt is called sodium chloride. It is considered a pure substance because it has a uniform and definite
composition. All samples of sodium chloride are chemically identical. Water is also a pure substance. Salt easily