Compounds Chapter 5, Section 2

10/26/10

Section 2 CompoundsChapter 5

Compounds: Made of Elements

• A compound is a pure substance composed of two or more elements that are chemically combined.

• Elements combine by reacting, or undergoing a chemical change, with one another.

• A chemical reaction is the process by which substances change into new substances.

Section 2 CompoundsChapter 5

Compounds: Made of Elements

• During a chemical reaction, the atoms of two or more elements react with each other to form molecules of compounds.

• When two or more elements combine, a new compound is formed. The properties of the new compound are different from the properties of the elements that formed the compound.

Compounds: Made of Elements, continued

Section 2 CompoundsChapter 5

Properties of Compounds

• Each compound has unique physical and chemical properties.

• A compound has properties that differ from the properties of the elements that make up the compound.

• Elements always join in a specific ratio to form a specific compound.

Section 2 CompoundsChapter 5

Breaking Down Compounds

• The only way to break down a compound is through a chemical change.

• Some compounds can be broken down into their elements.

• Other compounds can be broken down to form simpler compounds.

Section 2 CompoundsChapter 5

Compounds in Your World

• The compounds found in nature are not usually the raw materials needed by industry. Often, these compounds must be broken down to provide elements or other compounds that can be used as raw materials.

• Proteins and carbon dioxide are two compounds that play an important role in living things.