Chapter 2

Properties of Matter

Elements

An element is a substance that cannot be broken down into simpler substances.

Gold Aluminum Carbon Iodine

Elements

An atom is the smallest particle of an element.

An element has a fixed composition because it contains only one type of atom.

Compounds

A compound is a substance that is made from two or more elements and can be broken down into those elements.

Silicon

Oxygen

Silicon dioxide

Mixtures

A heterogeneous mixture is a mixture where the parts are noticeably different from one another.

Mixtures

A homogeneous mixture is a mixture where you cannot tell the difference between the parts of the mixture.

Mixtures

When substances dissolve and form a homogeneous mixture, that mixture is called a solution.

Mixtures

A suspension is a heterogeneous mixture that separates into layers over time.

Mixtures

A colloid contains some particles that are intermediate in size between the small particles in a solution and the larger particles in a suspension.

Colloids do not separate into layers.

You cannot use a filter to separate the parts of a colloid.

Physical Properties

A physical property is any characteristic of a material that can be observed or measured without changing the composition of the substances in the material.

Physical Properties

Conductivity is a material’s ability to allow heat or electricity to flow.

Physical Properties

Melting point is the temperature at which a substance changes from a solid to a liquid.

Physical Properties

Boiling point is the temperature at which a substance changes from a liquid to a gas

Using Properties to Separate Mixtures

Filtration is a process that separates materials based on their size.

Distillation is a process that separates liquids by their boiling points.

Physical Changes

A physical change occurs when some of the properties of a material change, but the substances in the material stay the same.

Observing Chemical Properties

A chemical property is any ability to produce a change in the composition of matter.

Chemical properties can be observed only during a chemical change.

Observing Chemical Properties

Reactivity describes the ability of a substance to chemically combine with other substances.

Observing Chemical Properties

Flammability is a material’s ability to burn in the presence of oxygen.

Recognizing Chemical Changes

A chemical change occurs when a substance reacts and forms one or more new substances.

Recognizing Chemical Changes

Three common indicators of a chemical change are a change in color, the production of a gas, and the formation of a precipitate.

Is a Change Chemical or Physical

When matter undergoes a chemical change, the composition of the matter changes.

When matter undergoes a physical change, the composition of matter remains the same.