Classifying Matter

Contributor: April Stokes. Lesson ID: 10577

"What's the matter with you?" Answer: "Oh, atoms, molecules, compounds." Learn why you take up space, using video, diagrams and a mystery experiment, to learn about substances, compounds and mixtures!


Physical Science

learning style
personality style
Beaver, Golden Retriever
Grade Level
Intermediate (3-5), Middle School (6-8)
Lesson Type
Quick Query

Lesson Plan - Get It!


Do you matter? In fact, you do and you are! You have atoms and you take up space — so therefore, you are matter. Understanding matter helps you understand your world. What are the different types of matter?


Image, via Wikimedia Commons, is in the public domain.

What is matter?

  • Matter is anything that has mass and takes up space (volume).
  • Air is an example of matter because it has mass and volume.
  • Light and sound are not matter because they have no mass and no volume.

Every sample of matter is either an element, compound, or a mixture.

An element is a substance that cannot be broken down into simpler substances by chemical means. Examples: carbon, hydrogen, oxygen, helium

  • The smallest unit of an element is an atom, and each element is made up of one type of atom.
  • Elements are represented by one- or two- letter symbols (always a single capital letter or a capital letter followed by a lowercase letter).
    • Ex: Carbon's symbol is C and Helium's symbol is He.

A molecule is the smallest unit of a substance that behaves like the substance.

  • Atoms can join to make millions of molecules just as letters of the alphabet combine to form different words.

A compound is a substance made up of atoms of different elements.

  • Each molecule of a compound contains two or more elements that are chemically combined.
  • When elements combine to make compounds, they always combine in the same proportions.
  • Think of compounds as recipes. If you change the recipe, then you change the compound.
    • For example, 2 hydrogens combine with 1 oxygen (H20) to make water. If you add more hydrogens or more oxygens, then something other than water is made.

Compounds and elements are pure substances because they have fixed compositions and definite properties.

Mixtures are not pure substances because they do not have fixed compositions and definite properties.

  • Mixtures are NOT chemically combined.
  • Classified as heterogeneous or homogenous.
    • heterogeneous = can see the parts (Lucky Charms cereal or a garden salad)
    • homogenous = cannot see the parts; uniform (sweet tea or grape juice)

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