Chemical Properties Chapter 2 Section 3 Chemical Properties

Chemical Properties Chapter 2 Section 3

Chemical Properties • A property of matter that describes a substance’s ability to participate in chemical reactions is a chemical property. • When wood is burned, smoke and ash are created. These have very different properties than the wood. • Two types of chemical properties are flammability and reactivity.

Flammability • The ability of a substance to burn is flammability. • Wood is flammable. It can burn. • Smoke and ash, created from a burning piece of wood, are unable to burn. They are nonflammable. • Rubbing alcohol and oxygen are also flammable. They will burn.

Reactivity • The ability of two or more substances to combine and form new substances is reactivity. • An iron nail can react with oxygen in the air to form rust, or iron oxide. • Chrome, which is nonreactive with oxygen, will not rust.

Comparing Physical & Chemical Properties • Physical properties can be identified without changing the identity of the substance. • You can observe the physical properties of matter without changing the matter. • Examples of physical properties are density, shape, and state. • Chemical properties are not as easy to observe.

Comparing Properties • You can only see that wood is flammable when it is actually burning. • You can only see that an iron nail is reactive with oxygen after it has rusted.

Characteristic Properties • Properties that are most useful in identifying a substance are characteristic properties. • These properties are always the same no matter what size the sample is. • Some characteristic properties are physical, like density and solubility. • Others are chemical properties, like flammability and reactivity.

Chemical Changes • A chemical change happens when one or more substances change into new substances that have new and different properties. • Some clues that chemical changes are taking place are changes in color or odor, heat being produced, fizzing, foaming, sound, and/or light.

Physical vs. Chemical Changes • Physical changes do not change the composition of the substance. • Grinding baking soda into a fine powder is a physical change. The substance is still baking soda. • Mixing baking soda and vinegar is a chemical change. A new substance is formed.