Unit 1: Pre-AP Chem

Chemistry

Study of the composition, properties, and interactions of matter.

Matter

Anything that has mass and occupies space.

Theory

A testable explanation of a particular aspect of nature.

States of Matter

The three most common states are solids, liquids, and gases (with plasma as a fourth state).

Solids

State with definite shape and volume; particles are tightly packed and vibrate; often have a crystalline structure.

Liquids

State with definite volume that takes the shape of its container; particles are close and move while touching; no regular molecular pattern.

Gases

State with no definite shape or volume; particles far apart and moving rapidly; high entropy (disorder).

Plasma

Fourth state of matter; ionized gas containing charged particles; occurs in high-temperature environments like stars and lightning.

Law of Conservation of Matter

Matter is conserved in a closed system; in chemical reactions, total mass of reactants equals total mass of products.

Pure Substances

Substances with constant composition.

Elements

Pure substances that cannot be broken down by chemical changes; e.g., Gold (Au).

Compounds

Pure substances that can be broken down by chemical changes; consist of two or more elements chemically bonded; e.g., H2O.

Properties

Characteristics used to distinguish one substance from another.

Physical Property

A property observed without changing the chemical composition of the substance.

Density

Mass per unit volume, a common physical property.

Color

A physical property describing how an object appears to the eye.

Hardness

Resistance to scratching or indentation.

Melting Point

Temperature at which a solid changes to a liquid; a physical property.

Boiling Point

Temperature at which a liquid boils and becomes a gas; a physical property.

Electrical Conductivity

Ability of a material to conduct electricity; a physical property.

Physical Change

Change in the state or properties of matter without a change in chemical composition.

Examples of Physical Changes

Melting ice, tearing paper, boiling water, freezing Kool-aid, stretching putty; no new substances formed.

Chemical Property

A characteristic observed during a chemical reaction; relates to how a substance changes into another.

Chemical Change

A change that alters the chemical composition or identity; new substances are formed.

Chemical Reaction

Process where a chemical change occurs, producing one or more new substances.

Miscible

Capable of being mixed together to form a homogeneous solution.

Immiscible

Cannot be mixed to form a homogeneous solution.

Soluble

Able to be dissolved in a solvent.

Insoluble

Unable to be dissolved in a solvent.

Solution

A homogeneous mixture of solute and solvent (e.g., solid + liquid).

Solvent

Substance that dissolves another substance.

Solute

Substance dissolved in a solvent.

Aqueous Solution

Solution in which water is the solvent (e.g., salt solution NaCl).

Filtration

Separation method using a filter to separate a mixture when some particles are too large to pass through.

Distillation

Separation by differences in boiling points, using evaporation and condensation (also used for separating solids from liquids or two liquids).

Chromatography

Separation method where components travel up paper at different rates due to differing attractions to the medium.

Homogeneous Mixture

A mixture with uniform composition throughout (e.g., solutions).

Crystalline Structure

Regular geometric arrangement of atoms in a solid.

Entropy

Measure of disorder in a system; higher in gases as particles move in many directions.

Aqueous

Describes a solution where water is the solvent.