Chemical properties: Chemical properties are observed when changes occur in the identity of the matter in a substance. The color changes in plant leaves and flowers result from chemical reactions.

When a piece of copper is exposed to the air, rain, and sun, the copper will slowly react with the oxygen and form a new substance. The color will change from the orange of copper metal to the green of corroded copper, copper II oxide, CuO. This interaction between copper metal, Cu, and oxygen, O₂, is a chemical property.

When gold is exposed to air, nothing happens to the color. The gold and oxygen do not interact. You can say that one chemical property of gold is that it does not react with oxygen. Because gold is relatively unreactive it retains its luster and is used in jewelry.

Click here to see NASA video of space shuttle flights where hydrogen and oxygen react to power the vehicle. These are large scale chemical reactions. Propane grills, gas water heaters, charcoal grills and fireworks all rely on exothermic chemical reactions.

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