1.2: Phases and Classification of Matter

Matter

Anything that occupies space and has mass.

Solid

Rigid and possesses a definite shape.

Liquid

Flows and takes the shape of its container, except that it forms a flat or slightly curved upper surface when acted upon by gravity.

Gas

Takes both the shape and volume of its container.

Plasma

A gaseous state of matter that contains appreciable numbers of electrically charged particles.

Where does plasma occur naturally?

In the interiors of stars; it is also found in high-temperature environments such as lightning strikes.

Mass

A measure of the amount of matter in an object.

Weight

The force that gravity exerts on an object.

Difference between mass and weight

Weight changes as the force of gravity changes, but mass does not.

Law of conservation of matter

There is no detectable change in the total quantity of matter present when matter converts from one type to another (a chemical change) or changes among solid, liquid, or gaseous states (a physical change).

Pure substance

Has a constant composition. All specimens of a pure substance have exactly the same makeup and properties.

Element

Pure substances that cannot be broken down into simpler substances by chemical changes.

Compound

Pure substances that are comprised of two or more elements.

Mixture

Composed of two or more types of matter that can be present in varying amounts and can be separated by physical changes.

Heterogeneous mixture

A mixture with a composition that varies from point to point.

Homogeneous mixture

A mixture that exhibits a uniform composition and appears visually the same throughout.

Solution

Another name for a homogeneous mixture.

Atom

The smallest particle of an element that has the properties of that element and can enter into a chemical combination.

Molecule

Consists of two or more atoms joined by strong forces called chemical bonds.

Chemical bonds

Strong forces that join atoms together in a molecule.

Leucippus and Democritus

Greek philosophers who developed the first suggestion that matter is composed of atoms in the 5th century BCE.

John Dalton

A British schoolteacher and scientist who supported the atomic hypothesis with quantitative measurements in the early nineteenth century. His atomic theory became one of the central theories of chemistry, with some aspects still used with minor revisions.