Chapter 3 – Matter and Energy: Classification, Properties, and Energy Changes

Chapter 3 – Matter and Energy

Section 3.1: Classification of Matter

Matter is the material that makes up all things in the universe. In chemistry, matter is defined as anything that has mass and occupies space. The classification of matter is based on its composition and physical properties.

• Matter can be divided into pure substances and mixtures.

Pure Substances

• A pure substance is a form of matter with a fixed or definite composition.

• There are two types of pure substances:

  • Element: Composed of only one type of atom. Examples: Copper (Cu), Gold (Au).

  • Compound: Composed of two or more elements chemically combined in the same proportion. Example: Water (H2O), Hydrogen peroxide (H2O2).

Mixtures

• A mixture consists of two or more substances that are physically mixed but not chemically combined.

• Mixtures can be separated by physical methods.

• Types of mixtures:

  • Homogeneous mixture (solution): Composition is uniform throughout. Example: Brass (copper and zinc).

  • Heterogeneous mixture: Composition varies from one part of the mixture to another. Example: Water and copper.

Type	Definition	Example
Element	One type of atom	Copper (Cu)
Compound	Two or more elements chemically combined	Water (H2O)
Homogeneous mixture	Uniform composition	Brass (Cu and Zn)
Heterogeneous mixture	Non-uniform composition	Water and copper

Example: Gold bar (element), hydrogen peroxide (compound), brass (homogeneous mixture), sand and water (heterogeneous mixture).

Additional info: The periodic table organizes all known elements, each with unique properties and atomic structure.