Chapter 17Classification of Matter

Section 1: Composition of Matter

Substance—either an element or a compound

When all the atoms in a substance are alike, the substance is an element.

A compound is a substance with two or more elements combined in a fixed proportion.

Two or more substances that can be easily separated by physical means form a mixture.

Heterogeneous mixture—mixture of different and easily distinguishable materials

Colloid—heterogeneous mixture with larger particles that never settle; colloids scatter light in the Tyndall effect

A heterogeneous mixture containing a liquid in which visible particles settle is called a suspension.

Homogeneous mixture—contains two or more gaseous, liquid, or solid substances blended evenly; also called a solution

Section 2: Properties of Matter

Physical property—characteristics of a material which can be observed without changing the identity of the substances in the material; examples include color, shape, size, melting point, and boiling point

Appearance—physical description of a substance

Behavior—how a substance acts; for example, magnetism, viscosity, ductility

Physical properties such as size and magnetism can be used to separate mixtures.

Physical change—change in a substance’s size, shape, or state of matter

Substance does not change identity when it undergoes a physical change

Distillation is a process for separating a mixture by evaporating a liquid and condensing its vapor.

Chemical property—characteristics of a substance indicating that it can change chemically; for example, flammability or light sensitivity of a substance

When one substance changes to another substance, a chemical change has occurred. Some chemical changes are indicated by

temperature change, smell, or bubble formation.

Other chemical changes occur very slowly such as the formation of rust.

Chemical changes can be used to separate substances such as metals from their ores.

Weathering of Earth’s surface involves both physical and chemical changes.

Physical—big rocks split into smaller ones; streams carry rock particles from one location to another

Chemical—Chemical changes can occur in rocks when calcium carbonate in limestone changes to calcium hydrogen carbonate due to acid rain.

Rock Cycle

Law of Conservation of Mass—Mass of all substances present before a chemical change equals the mass of all substances after the change.

1. Which element makes up greater than 50 percent of the elements dissolved in seawater?

A Sodium B Sulfur

C Magnesium D Chlorine

2. Which element is found dissolved in seawater about twice as much as magnesium?

F Calcium G Sodium

H Sulfur J Potassium

3. Which of the following is a compound?

A Ca B MgS C Cl2 D Na

Classify the following as a mixture or pure substance, and atom, molecule, or

compound.

A. B. C. D.

E. F. G. H.

I. J. K. L.