Chemistry: Unit 3 Vocabulary

Oxyacid

any acid that contains hydrogen and an oxyanion

Covalent bond

a chemical bond that results from the sharing of valence electrons

Molecule

forms when two or more atoms covalently bond and is lower in potential energy that its constituent atoms

Lewis structure

a model that uses electron-dot structures to show how electrons are arranged in molecules.

Sigma bond

a single covalent bond that is formed when an electron pair is shared by the direct overlap of bonding orbitals

Endothermic reaction

a chemical reaction or process in which a greater amount of energy is required to break the existing bonds in the reactants than is released when the new bonds form in the product molecules

Exothermic reaction

a chemical reaction or process in which more energy is released than is required to break bonds in the initial reactants

Structural formula

a molecular model that uses symbols and bonds to show relative positions of atoms; can be predicted for many molecules by drawing the Lewis structure.

Resonance

condition that occurs when more than one valid Lewis structure exists for the same molecule

Coordinate covalent bond

forms when one atom donates a pair of electrons to be shared with an atom or ion that needs two electrons to become stable.

Pi bond

a bond that is formed when parallel orbitals overlap to share electrons

VSEPR model

Valence Shell Electron Pair Repulsion model

Hybridization

a process in which atomic orbitals are mixed to form new

Polar covalent bond

a type of bond that forms when electrons are not shared equally

Chemical reaction

the process by which the atoms of one or more substances are rearranged to form different substances; occurrence can be indicated by changes in temperature

Reactant

the starting substance in a chemical reaction

Product

a substance formed during a chemical reaction

Chemical equation

a statement using chemical formulas to describe the identities and relative amounts of the reactants and products involved in the chemical reaction

Coefficient

In a chemical equation

Synthesis reaction

a chemical reaction in which two or more substances react to yield a single product.

Combustion reaction

a chemical reaction that occurs when a substance reacts with oxygen

Decomposition reaction

a chemical reaction that occurs when a single compound breaks down into two or more elements or new compounds

Single replacement reaction

a chemical reaction that occurs when the atoms of one element replace the atoms of another element in a compound

Double replacement reaction

a chemical reaction that involves the exchange of ions between two compounds and produces either a precipitate

Precipitate

a solid produced during a chemical reaction in solution

Aqueous solution

a solution in which the solvent is water

Solute

one or more substances dissolved in a solution

Solvent

the substance that dissolves a solute to form a solution; the most plentiful substance in the solution

the mobile phase in paper chromatography (the molecules that can move)

Complete ionic equation

an ionic equation that shows all the particles in a solution as they realistically exist

Spectator ion

ion that does not participate in a reaction

Net ionic equation

an ionic equation that includes only the particles that participate in the reaction

Linear

2 bonded pairs and 0 lone pairs on central atoms

Bent

2 bonded pairs and either 1 or 2 lone pairs on central atoms

Trigonal Planar

3 bonded pairs and 0 lone pairs on central atoms

Tetrahedral

4 bonded pairs and 0 lone pairs on central atoms

Chromatography

Chromatography is a chemical analysis technique used to separate substances in a mixture based on their movement through a special paper

Uses of Chromatography

To separate a mixture of soluble substances in liquids

The baseline

The name given to the pencil line in paper chromatography. Should not be submerged in the solvent.

A chromatogram

the name of the resulting paper we end up with in paper chromatography

Water and Ethanol

Solvents that are commonly used in chromatography

Distillation

Separates substances on the basis of the boiling points of the substances

Crystallization

Separates by formation of solid, pure particles from a solution

Filtration

Separates solids from liquids by using a porous barrier

Heterogenous mixtures

a mixture in which the composition is not uniform throughout the mixture.

EX: Chocolate Chip Cookie, sand-water mixture

Homogenous mixtures

a mixture in which the composition is uniform throughout the mixture.

EX: salt-water mixture