Honors Chemistry - Chemistry, Matter and Chemical Formulas

Vocabulary flashcards covering key concepts from the Honors Chemistry lecture on Matter and Chemical Formulas.

Chemistry

The study of MATTER, its changes and the energy involved in the changes.

Matter

Anything that has mass and volume.

Pure Substance

Matter that is uniform and has specific chemical and physical properties.

Element

Building blocks of all matter; cannot be separated further by chemical means; exists as one type of atom with the same number of protons.

Compound

A pure substance formed by a combination of two or more different elements in a fixed, whole number ratio, held together by chemical bonds; properties differ from individual elements.

Mixture

A physical combination of substances with a variable composition; no chemical reaction occurs between components.

Atom

The basic unit of an element, defined by its atomic number (number of protons).

Molecule

A bonded group of non-metal atoms; neutral and held together by covalent bonds (sharing electrons).

Formula Unit

Represents the simplest ratio of ions in an ionic compound, forming an attracted, geometric pattern of positive (metal) and negative (non-metal) ions.

Physical Property

A characteristic of a substance that can be observed or measured without changing the substance's identity or composition.

Chemical Property

A characteristic of a substance that describes whether it reacts or does not react with other substances.

Physical Change

A change in the form or appearance of a substance, but not its chemical identity or composition.

Chemical Change

A change that results in the formation of new substances with different chemical identities and compositions. Also called a chemical reaction.

Homogeneous Mixture (Solution)

A mixture with uniform composition where molecules are evenly spread out, and no visible boundaries exist between components.

Heterogeneous Mixture

A mixture with non-uniform composition, having visible boundaries or distinct phases.

Chemical Reaction

The rearrangement of atoms into new substance(s) by making and breaking bonds with a change in energy.

Reactants

The starting substances involved in a chemical reaction.

Products

The new substances formed as a result of a chemical reaction.

Law of Conservation of Mass

States that the mass of substances before a chemical reaction equals the mass of the substances after the reaction; mass is neither created nor destroyed.

Law of Conservation of Mass and Energy

States that matter and energy are never created or destroyed, they just change form; the total amount is constant.

Coefficient

A number placed in front of a chemical formula to indicate the number of molecules or formula units of the substance; it multiplies the entire formula.

Subscript

A number written lower than the line in a chemical formula indicating the number of atoms of a specific element present in a molecule or formula unit.

Law of Definite Composition

States that any given compound always contains the same fixed ratio of elements/atoms by mass.

Law of Multiple Proportions

States that elements can combine in different fixed, simple whole-number ratios to form different compounds.

Criss-cross Method

A technique used in writing ionic formulas where the numerical value of the charge of one ion becomes the subscript of the other ion.

Roman Numeral

Used in chemical naming to indicate the positive charge of a metal ion, particularly for transition metals that can have multiple oxidation states.

Polyatomic Ion

An ion composed of two or more atoms covalently bonded together that acts as a single unit with an overall charge.