Chapter 4: Chemical Reactions

Vocabulary terms covering matter properties, changes, reaction classifications, energy changes, and stoichiometry from Chapter 4.

Physical Properties

Properties that can be observed or measured without changing or destroying the composition of the matter, leaving the matter the same after measuring.

Chemical Properties

Properties that can be observed or measured only when matter changes or attempts to change into new substances.

Physical Changes

Changes that occur without a change in composition and do not produce a new substance.

Chemical Changes

Changes that occur with a change in composition and produce a new substance.

Law of Conservation of Mass

The principle stating that matter is neither created nor destroyed, meaning a reaction must end with the same types of atoms that it started with.

$$(aq)$$

A subscript state symbol indicating that a substance is dissolved in water.

Subscript (in a Chemical Formula)

A number in a chemical formula that indicates the quantity of a specific atom in a molecule (e.g., $O_2$ contains 2 oxygen atoms).

Coefficient

A number placed in front of a chemical formula that indicates the quantity of the molecule in the reaction.

Combination Reaction

A reaction (also called an addition or synthesis reaction) where 2 substances react to form a single new compound ($A + B \rightarrow AB$).

Decomposition Reaction

A reaction in which one compound is broken down into 2 or more simpler substances ($AB \rightarrow A + B$).

Combustion Reaction

A chemical reaction whose reactants include $O_2$ and whose products include heat, $H_2O$, and $CO_2$ (or $CO$ if there is insufficient $O_2$).

Single Replacement Reaction

A chemical reaction in which a free element takes the place of an element in a compound ($AB + C \rightarrow AC + B$).

Double Replacement Reaction

A reaction occurring between two substances dissolved in water in which the ion pairs of the two molecules switch places ($AB + CD \rightarrow AD + CB$).

Exothermic Reaction

A chemical reaction in which energy is released (such as in the form of heat, light, or sound).

Endothermic Reaction

A chemical reaction in which energy is absorbed.

Stoichiometry

The study of mass relationships in chemical reactions that uses balanced equations to calculate quantities of molecules, moles, or grams needed or produced.