UNIT OVERVIEW

Oxygen makes up about 21% of the air around us. It is a very reactive gas. This means oxygen easily combines with other substances to form new products.

Some reactions with oxygen happen slowly. Rust on a gate takes weeks or months to appear. Other reactions happen fast. A match bursts into flame in seconds.

In this unit, you will learn:

• How metals react with oxygen to form metal oxides
• What rust is, how it forms, and how to stop it
• How non-metals react with oxygen
• Why some oxides cause problems like acid rain and air pollution

Why this matters:

Understanding these reactions helps you know why cars rust, why we paint metal roofs, and why factories must control the gases they release.

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