Key Terms

acid

molecule that donates hydrogen ions and increases the concentration of hydrogen ions in a solution

adhesion

attraction between water molecules and other molecules

aliphatic hydrocarbon

hydrocarbon consisting of a linear chain of carbon atoms

anion

negative ion that is formed by an atom gaining one or more electrons

aromatic hydrocarbon

hydrocarbon consisting of closed rings of carbon atoms

atom

the smallest unit of matter that retains all of the chemical properties of an element

atomic mass

calculated mean of the mass number for an element’s isotopes

atomic number

total number of protons in an atom

balanced chemical equation

statement of a chemical reaction with the number of each type of atom equalized for both the products and reactants

base

molecule that donates hydroxide ions or otherwise binds excess hydrogen ions and decreases the concentration of hydrogen ions in a solution

buffer

substance that prevents a change in pH by absorbing or releasing hydrogen or hydroxide ions

calorie

amount of heat required to change the temperature of one gram of water by one degree Celsius

capillary action

occurs because water molecules are attracted to charges on the inner surfaces of narrow tubular structures such as glass tubes, drawing the water molecules to the sides of the tubes

cation

positive ion that is formed by an atom losing one or more electrons

chemical bond

interaction between two or more of the same or different atoms that results in the formation of molecules

chemical reaction

process leading to the rearrangement of atoms in molecules

chemical reactivity

the ability to combine and to chemically bond with each other

cohesion

intermolecular forces between water molecules caused by the polar nature of water; responsible for surface tension

compound

substance composed of molecules consisting of atoms of at least two different elements

covalent bond

type of strong bond formed between two of the same or different elements; forms when electrons are shared between atoms

dissociation

release of an ion from a molecule such that the original molecule now consists of an ion and the charged remains of the original, such as when water dissociates into H⁺ and OH^-

electrolyte

ion necessary for nerve impulse conduction, muscle contractions and water balance

electron

negatively charged subatomic particle that resides outside of the nucleus in the electron orbital; lacks functional mass and has a negative charge of –1 unit

electron configuration

arrangement of electrons in an atom’s electron shell (for example, 1s²2s²2p⁶)

electron orbital

how electrons are spatially distributed surrounding the nucleus; the area where an electron is most likely to be found

electron transfer

movement of electrons from one element to another; important in creation of ionic bonds

electronegativity

ability of some elements to attract electrons (often of hydrogen atoms), acquiring partial negative charges in molecules and creating partial positive charges on the hydrogen atoms

element

one of 118 unique substances that cannot be broken down into smaller substances; each element has unique properties and a specified number of protons

enantiomers

molecules that share overall structure and bonding patterns, but differ in how the atoms are three dimensionally placed such that they are mirror images of each other

equilibrium

steady state of relative reactant and product concentration in reversible chemical reactions in a closed system

evaporation

separation of individual molecules from the surface of a body of water, leaves of a plant, or the skin of an organism

functional group

group of atoms that provides or imparts a specific function to a carbon skeleton

geometric isomer

isomer with similar bonding patterns differing in the placement of atoms alongside a double covalent bond

heat of vaporization of water

high amount of energy required for liquid water to turn into water vapor

hydrocarbon

molecule that consists only of carbon and hydrogen

hydrogen bond

weak bond between slightly positively charged hydrogen atoms to slightly negatively charged atoms in other molecules

hydrophilic

describes ions or polar molecules that interact well with other polar molecules such as water

hydrophobic

describes uncharged non-polar molecules that do not interact well with polar molecules such as water

inert gas

(also, noble gas) element with filled outer electron shell that is unreactive with other atoms

ion

atom or chemical group that does not contain equal numbers of protons and electrons

ionic bond

chemical bond that forms between ions with opposite charges (cations and anions)

irreversible chemical reaction

chemical reaction where reactants proceed uni-directionally to form products

isomers

molecules that differ from one another even though they share the same chemical formula

isotope

one or more forms of an element that have different numbers of neutrons

law of mass action

chemical law stating that the rate of a reaction is proportional to the concentration of the reacting substances

litmus paper

(also, pH paper) filter paper that has been treated with a natural water-soluble dye that changes its color as the pH of the environment changes so it can be used as a pH indicator

mass number

total number of protons and neutrons in an atom

matter

anything that has mass and occupies space

molecule

two or more atoms chemically bonded together

neutron

uncharged particle that resides in the nucleus of an atom; has a mass of one amu

noble gas

see inert gas

nonpolar covalent bond

type of covalent bond that forms between atoms when electrons are shared equally between them

nucleus

core of an atom; contains protons and neutrons

octet rule

rule that atoms are most stable when they hold eight electrons in their outermost shells

orbital

region surrounding the nucleus; contains electrons

organic molecule

any molecule containing carbon (except carbon dioxide)

periodic table

organizational chart of elements indicating the atomic number and atomic mass of each element; provides key information about the properties of the elements

pH paper

see litmus paper

pH scale

scale ranging from zero to 14 that is inversely proportional to the concentration of hydrogen ions in a solution

polar covalent bond

type of covalent bond that forms as a result of unequal sharing of electrons, resulting in the creation of slightly positive and slightly negative charged regions of the molecule

product

molecule found on the right side of a chemical equation

proton

positively charged particle that resides in the nucleus of an atom; has a mass of one amu and a charge of +1

radioisotope

isotope that emits radiation composed of subatomic particles to form more stable elements

reactant

molecule found on the left side of a chemical equation

reversible chemical reaction

chemical reaction that functions bi-directionally, where products may turn into reactants if their concentration is great enough

solvent

substance capable of dissolving another substance

specific heat capacity

the amount of heat one gram of a substance must absorb or lose to change its temperature by one degree Celsius

sphere of hydration

when a polar water molecule surrounds charged or polar molecules thus keeping them dissolved and in solution

structural isomers

molecules that share a chemical formula but differ in the placement of their chemical bonds

substituted hydrocarbon

hydrocarbon chain or ring containing an atom of another element in place of one of the backbone carbons

surface tension

tension at the surface of a body of liquid that prevents the molecules from separating; created by the attractive cohesive forces between the molecules of the liquid

valence shell

outermost shell of an atom

van der Waals interaction

very weak interaction between molecules due to temporary charges attracting atoms that are very close together