High School Chemistry Vocabulary

Includes vocabulary concerning: chemical reactions, stoichiometry, states of matter, the behavior of gases, water and aqueous systems, solutions, thermochemistry

a solid undergoes sublimation when...

vapor pressure > atmospheric pressure

acid dissociation constant K_a

the ratio of the concentration of the dissociated form of an acid to the concentration of the undissociated form; stronger acids have a bigger number than weaker acids

acid-base reaction

a reaction in which an acid and a base react in an aqueous solution to produce a salt and water; it is a double-replacement reaction and produces a neutral solution.

activity series

a list of elements in order of decreasing activity

activity series of halogens

fluorine, chlorine, bromine, iodine

actual yield

the amount of product that forms when a reaction is carried out in the laboratory

adsorption

the process of adhering to a surface

aliphatic compound

any compound not classified as an aromatic compound

aliphatic hydrocarbons

any straight-chain or branched-chain alkane, alkene, or alkyne; not aromatic

alkane

a hydrocarbon containing only single covalent bonds; these are saturated hydrocarbons

alkene

a hydrocarbon containing one or more carbon-carbon double bonds; these are unsaturated hydrocarbons

alkyl group

a hydrocarbon substituent; the methyl group (-CH3) is an example

alkyne

a hydrocarbon containing a carbon-carbon triple bond; these are unsaturated hydrocarbons

allotropes

two or more different molecular forms of the same element in the same physical state

alpha particle

a positively charged particle emitted from certain radioactive nuclei; it consists of two protons and two neutrons and is identical to the nucleus of a helium atom

amorphous solid

a solid that lacks an ordered internal structure; its atoms are randomly arranged (e.g. rubber, plastic, asphalt)

anhydrous

describes a substance that does not contain water

aqueous solution

water that contains dissolved substances

aromatic compound

an organic compound that contains a benzene ring or other ring in which the bonding is like that of benzene; also known as arenes

asymmetric carbon

a carbon atom that has four different atoms or groups attached

balanced equation

a chemical equation in which mass is conserved; each side of the equation has the same number of atoms of each element

band of stability

the location of stable nuclei on a neutron-vs.-proton plot

beta particle

an electron resulting from the breaking apart of neutrons in an atom

branched-chain alkane

an alkane with one or more alkyl groups attached to the parent structure

brownian motion

the chaotic movement of colloidal particles, caused by collision with particles of the solvent in which they are dispersed

buffer

a solution in which the pH remains relatively constant when small amounts of acid or base are added; can be either a solution of a weak acid and the salt of a weak acid or a solution of a weak base with the salt of a weak base

buffer capacity

a measure of the amount of acid or base that may be added to a buffer solution before a significant change in pH occurs

calorimeter

an insulated device used to measure the absorption or release of heat in chemical or physical processes

calorimetry

the precise measurement of heat flow out of a system for chemical or physical processes

catalyst

a substance that increases the rate of reaction by lowering the activation-energy barrier; is not used up in the reaction

chemical energy/chemical potential energy

energy stored in chemical bonds

chemical equation

an expression representing a chemical reaction; the formulas of the reactants (on the left) are connected by an arrow with the formulas for the products (on the right)

chemical formula for hydrates

formula of compound + "・" + number of water molecules per formula unit

cis configuration

the configuration in which substituent groups are on the same side of a double bond

cis-trans isomers

compounds that have atoms in the same order, but differ in the orientation of groups around a double bond

coagulation

the action or process of a liquid changing to a solid or semi-solid state.

coefficient

a small whole number that appears in front of a formula in a balanced chemical equation

colligative property

a property that depends only upon the number of solute particles, and not upon their identity

colloid

a mixture whose particles are intermediate in size between those of a suspension and a solution

combination reaction general equation

R + S → RS

combination reaction; synthesis reaction

a chemical change in which two or more substances react to form a single new substance

combustion reaction

a chemical change in which an element or a compound reacts with oxygen, often producing energy in the form of heat and light

combustion reaction general equation

CₓHᵧ + (x + y/4)O₂ → xCO₂ + (y/2)H₂O

complete ionic equation

an equation that shows dissolved ionic compounds as dissociated free ions

concentration

a measurement of solute that is a dissolved in a given quantity of solvent; usually expressed as mol/L

condensed structural formula

a structural formula that leaves out some bonds and/or atoms; the presence of these atoms or bonds is understood

constitutional isomers

compounds that have the same molecular formula, but whose atoms are bonded in a different order

cracking

the controlled process by which hydrocarbons are broken down or rearranged into smaller, more useful molecules

crystal

a solid in which the atoms, ions, or molecules are arranged in an orderly, repeating, three-dimensional pattern called a crystal lattice

crystal lattice

a repeating array of any one of fourteen kinds of unit cells

cyclic hydrocarbon

an organic compound that contains a hydrocarbon ring

cycloalkane

cyclic hydrocarbon that contains only single bonds

decomposition reaction

a chemical change in which a single compound is broken down into two or more simpler products

decomposition reaction general equation

RS → R + S

deliquescent

describes a substance that removes sufficient water from the air to form a solution; the solution formed has a lower vapor pressure than that of the water in the air

desiccant

a hygroscopic substance used as a drying agent

diffusion

the tendency of molecules to move toward areas of lower concentration until the concentration is uniform throughout

dilute solution

a solution that contains a small amount of solute relative to the solvent

dilution

the process of preparing a less concentrated solution from a more concentrated one by adding solvent

dispersed medium

solid, liquid, or gas in which colloidal particles are dispersed

dispersed phase

colloidal particles spread throughout a suspension

dissociation

the process by which an ionic compound separates into ions when in an aqueous solution.

dissolution

the process by which one substance (the solute) dissolves into another (the solvent)

double-replacement reaction

a chemical change that involves an exchange of positive ions between two compounds

double-replacement reaction general equation

[R⁺ S⁻] + [T⁺ U⁻] → [R⁺ U⁻] + [T⁺ S⁻]

effloresce

to lose water of hydration

electrolyte

a compound that conducts an electric current when it is in an aqueous solution or in the molten state (most are ionic compounds, but a few are covalent)

elements that have allotropes

carbon, phosphorus, sulfur, oxygen, boron, and antimony

emulsifying agent

allows the formation of colloidal dispersions between liquids that don't ordinarily mix

emulsion

the colloidal dispersion of one liquid into another

enantiomers

molecules that differ from one another in the way that four different groups are arranged around a carbon atom

end point

the point in a titration at which the indicator changes color

enthalpy

The heat content of a system at constant pressure

equivalence point

the point in a titration where the number of moles of hydrogen ions equals the number of moles of hydroxide ions

excess reagent

a reagent present in a quantity that is more than sufficient to react with a limiting reagent; any reactant that remains after the limiting reagent is used up in a chemical reaction

film badge

a radiation detection device that consists of several layers of photographic film covered with black lightproof paper, all encased in a plastic or metal holder

fission

the splitting of a nucleus into smaller fragments, accompanied by the release of neutrons and a large amount of energy

fusion

the process of combining nuclei to produce a nucleus of greater mass

gamma ray

a high-energy photon emitted by a radioisotope

geiger counter

a device that uses a gas-filled metal tube to detect radiation

glass

a transparent fusion product of inorganic substances that have cooled to a rigid state without crystallizing

Graham's law of effusion (diffusion)

the rate of effusion of a gas is inversely proportional to the square root of the gas' molar mass

Graham's law of effusion equation

Rate of effusion A/Rate of effusion B = sqrt(molar mass B/molar mass A)

half-life (t½)

the time required for one half of the nuclei of a radioisotope sample to decay to products

half-reaction

an equation showing either the oxidation or the reduction that takes place in a redox reaction

half-reaction method

a method of balancing a redox equation by balancing the oxidation and reduction half-reactions separately before combining them into a balanced redox equation

heat capacity

the amount of heat needed to increase the temperature of an object exactly 1°C

heat of combustion

the heat of reaction for the complete burning of one mole of a substance

heat of reaction

the enthalpy change for the chemical equation exactly as it is written

heat/thermal energy

energy that transfers from one object to another because of temperature difference between the objects

Henry's law

at a given temperature the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid

Hess' law of heat summation

if you add two or more thermochemical equations to give a final equation, then you can also add the heats of reaction to give the final heat of reaction

homologous series

a group of compounds in which there is a constant increment of change in molecular structure from one compound in the series to the next

adsorbing

colloidal particles become charged by _____ ions from the dispersing medium onto their surface

hydrate

a compound that has a specific number of water molecules bound to each formula unit (e.g. atoms, molecules)

hydrocarbon

an organic compound that contains only carbon and hydrogen

hygroscopic

a term describing salts and other compounds that remove moisture from the air (e.g. carbon chloride)

immiscible

describes liquids that are insoluble in one another

ion-product constant for water (K_w)

the product of the concentrations of hydrogen and hydroxide ions in water; it is 1 x 10^-14 at 25°C

ionizing radiation

radiation with enough energy to knock electrons off some atoms of a bombarded substance to produce ions