Chem 2 AP Test Review

Matter

Classified as pure substances or mixtures.

Pure substances

Either elements or compounds.

Element

Substance composed of atoms having the same number of protons.

Compound

Combination of two or more chemically bonded elements in a specific ratio.

Mixtures

Consist of two or more substances.

Homogeneous mixtures

Uniform throughout. Examples: Air, seawater, mixture of metals (alloys).

Heterogeneous mixtures

Vary in texture and appearance throughout sample. Examples: Rocks, muddy water.

Physical properties

Can be measured without changing the identity or composition of the substance. Include odor, density, melting point, and hardness.

Chemical properties

Describe the way a substance changes (reacts) to form other substances. Example: The flammability of gasoline → reacts with O2 to form CO2 and H2O.

Intensive properties

Type of substance. Examples: Temperature, density, and boiling point.

Extensive properties

Depend on the quantity(amount) of the sample. Examples: Energy content, mass, and volume.

Physical change

Changes in the appearance of a substance but does not change its composition. Example: Phase changes.

Chemical change

Chemical reaction that transforms a substance into a different substance or substances.

Filtration

Separates a solid from a liquid.

Distillation

Separates substances based on their differences in boiling points.

Chromatography

A technique that separates substances based on differences in intermolecular forces and their abilities to dissolve in various solvents.

Measurement

Chemists use SI units

Volume

1L = 1000 cm3 = 1000 mL. 1 cm3 = 1 mL.

Density

Mass/volume. g/cm3 for liquids, g/L for gases.

Accuracy

close to the ACTUAL value

Precision

multiple values that are around the same, (not necessarily accurate to the ACTUAL value)