Composition of Pure Substances and Mixtures

Vocabulary flashcards covering pure substances, empirical and molecular formulas, Law of Definite Proportions, hydrates, combustion analysis, mixtures, and gravimetric analysis.

Pure Substance

A form of matter containing atoms, molecules, or formula units of a single type.

Empirical Formula

A chemical formula that gives the least ratio of atoms in a compound.

Molecular Formula

A chemical formula that gives the actual number of atoms in a compound and is always a multiple of the empirical formula.

Law of Definite Proportions

Proust's Law stating that a specific chemical compound always contains its component elements in a fixed ratio by mass.

Hydrate

A solid compound containing water molecules combined in a definite ratio as an integral part of the crystal.

Combustion Analysis

A method to determine the empirical formula of compounds containing $C$, $H$, and sometimes $O$ by burning them in excess oxygen and analyzing the resulting $CO_2$ and $H_2O$.

Mixture

A form of matter containing molecules or formula units of two or more types whose relative proportions can vary.

Classification of Matter

The organizational hierarchy dividing matter into pure substances (elements and compounds) and mixtures (homogeneous and heterogeneous).

Homogeneous Mixture

A mixture (solution) that has a uniform composition throughout, such as salt water, mouthwash, or alloys.

Heterogeneous Mixture

A mixture with distinct phases and non-uniform composition throughout, such as pizza, Italian salad dressing, or a solid waste dump.

Gravimetric Analysis

A quantitative laboratory technique involving weighing a sample, dissolving it, forming a precipitate, filtering, and repeatedly drying and weighing until a constant mass is obtained.