Term
click below
click below
Term
Normal Size Small Size show me how
Chemistry
Term | Definition |
---|---|
Atom | Fundamental building blocks of ordinary matter |
Molecule | Two or more atoms joined together by chemical bonds |
Chemistry | Study of matter |
Hypothesis | Interpretation or explanation of observed phenomena |
Experiment | Procedure intended to confirm or refute a hypothesis |
Scientific Law | Brief statement that summarizes observations and predicts future phenomena |
Scientific Theory | Model and explanation for natural occurrences and phenomena |
Law of Conservation of Mass | Matter is neither created nor destroyed during a chemical reaction |
Atomic Theory | Theory that matter is composed of small and indestructible particles called atoms |
Matter | Anything that occupies space and has mass |
Substance | Any specific instance of matter |
State | Physical form of matter |
Composition | Chemical makeup of matter |
Solid | State of matter with a definite shape and volume; particles are packed close to one another |
Liquid | State of matter with a definite volume but no definite shape; particles are free to move relative to each other |
Gas | State of matter with no definite shape or volume; particles will fill the container that the substance is in |
Pure Substance | Substance made of only one component |
Mixture | Substance made of two or more components |
Heterogenous Mixture | Mixture in which the composition varies from one region of the mixture to another |
Homogenous Mixture | Mixture in which the composition is the same throughout |
Element | Substance that cannot be chemically broken down into simpler substances |
Compound | Substance composed of two or more elements |
Decanting | Method of separating immiscible liquids by pouring the top layer into another container |
Distillation | Process by which a mixture is heated to boil off the more volatile liquid |
Filtration | Process by which a mixture composed of an insoluble solid and a liquid are separated by pouring the mixture through filter paper or some other porous membrane or layer |
Physical Change | Change that only alters the state or appearance, not the composition, of matter |
Chemical Change | Change that alters the chemical composition of matter |
Physical Property | Property that a substance displays without changing its composition |
Chemical Property | Property that a substance displays only by changing its chemical composition |
Units | Standard Quantities used to specify measurements |
International System of Units (SI Units) | Standard unit system used by scientists. |
Mass | Quantity of matter within an object |
Temperature | Measure of the average kinetic energy of the atoms or molecules that compose matter |
Fahrenheit Scale | Temperature scale where water freezes at 32° and boils at 212° |
Celsius Scale | Temperature scale where water freezes at 0° and boils at 100° |
Kelvin Scale | Temperature scale where zero is the coldest temperature possible |
Absolute Zero | Temperature at which molecular motion virtually stops; 0 Kelvin |
Meter (m) | SI unit of length |
Kilogram (kg) | SI unit of mass |
Second (s) | SI unit of time |
Kelvin (K) | SI unit of temperature |
Mole (mol) | SI unit of amount of substance |
Ampere (A) | SI unit of electric current |
Candela (cd) | SI unit of luminous intensity |
Exa (E) | Prefix multiplier equal to 10^18 |
Peta (P) | Prefix multiplier equal to 10^15 |
Tera (T) | Prefix multiplier equal to 10^12 |
Giga (G) | Prefix multiplier equal to 10^9 |
Mega (M) | Prefix multiplier equal to 10^6 |
Kilo (k) | Prefix multiplier equal to 10^3 |
Hecto (h) | Prefix multiplier equal to 10^2 |
Deca (da) | Prefix multiplier equal to 10^1 |
Deci (d) | Prefix multiplier equal to 10^-1 |
Centi (c) | Prefix multiplier equal to 10^-2 |
Milli (m) | Prefix multiplier equal to 10^-3 |
Micro (µ) | Prefix multiplier equal to 10^-6 |
Nano (n) | Prefix multiplier equal to 10^-9 |
Pico (p) | Prefix multiplier equal to 10^-12 |
Femto (f) | Prefix multiplier equal to 10^-15 |
Atto (a) | Prefix multiplier equal to 10^-18 |
Derived Unit | Combination of base units |
Volume | Measure of space. Equal to any unit of length cubed |
Liter (L) | Common unit of volume equal to one thousand milliliters |
Density (d) | Ratio of a substance's mass to its volume |
Intensive Property | Property that is independent of the amount of a substance |
Extensive Property | Property that is dependent on the amount of a substance |
Significant Figures | Non-placeholding digits that indicate the precision of a measured quantity |
Exact Numbers | Numbers with no uncertainty. They do not limit the number of significant figures in a calculation |
Accuracy | How close a measured value is to the actual value |
Precision | How close a series of measurements are to one another |
Random Error | Error that has equal probability of being too high or too low |
Systematic Error | Error that tends to be consistently either too high or too low |
Conversion Factor | Ratio used to convert from one unit to another |
Dimensional Analysis | Use of units and conversion factors in calculations |
Brownian Motion | Random motion of particles suspended in a liquid or gas |
Law of Definite Proportions | All samples of a given compound have the same proportions of constituent elements |
Law of Multiple Proportions | When two elements form two different compounds, the masses of the first element that combine with one gram of the second element can be expressed as a ratio of small whole numbers |
Electric Charge | Tendency of certain particles to experience a force in the presence of electric fields |
Proton | Positively charged particle found in the nucleus. It has the same mass as the neutron |
Neutron | Neutrally charged particle found in the nucleus. It has the same mass as the proton |
Electron | Negatively charged, low-mass particle present in all atoms. Orbits the nucleus |
JJ Thomson | English physicist who discovered the electon |
Robert Millikan | American physicist who deduced the electron's charge |
Cathode Ray | Stream of electrons produced when a high electrical voltage is applied between two electrodes within a partially evacuated tube |
Nucleus | Very small, dense core of an atom. It contains protons and neutrons |
Atomic Mass Unit (amu) | Unit used to express the masses of atoms and subatomic particles. It is defined as one-twelfth of the mass of a carbon atom containing six protons and six neutrons (carbon-twelve) |
Atomic Number | Number of protons in an atom's nucleus. Denoted by the letter Z |
Chemical Symbol | One or two letter abbreviation for a chemical element |
Isotopes | Atoms with the same number of protons but different numbers of electrons |
Natural Abundance | Relative percentage of a particular isotope in a naturally occurring sample with respect to other isotopes |
Mass Number | Sum of the number of neutrons and protons in an atom. Denoted by the symbol A |
Ion | Atom or molecule with a net charge. Caused by the gain or loss of electrons |
Cation | Ion with a positive net charge |
Anion | Ion with a negative net charge |
Periodic Law | Arranging elements in order of increasing mass produces recurring sets of certain properties |
Metals | Elements that are good conductors, malleable, ductile, lustrous, and tend to lose electrons during reactions |
Nonmetals | Elements that are poor conductors and tend to gain electrons during reactions |
Metalloids | Elements that are found on the border of metals and nonmetals, and exhibit intermediate properties |
Main-Group Elements | Elements in the 's' or 'p' blocks. They have easily predictable properties |
Transition Elements | Elements in the 'd' block. Their properties are less predictable |
Family (Group) | Column of the periodic table |
Period | Row of the periodic table |
Alkali Metals | Group 1A elements. They are highly reactive (Lithium, Potassium, Sodium, etc.) |
Alkaline Earth Metals | Group 2A elements. They are fairly reactive (Calcium, Beryllium, Magnesium, etc.) |
Boron Group | Group 3A elements. They have three valence electrons (Boron, Aluminum, Indium, etc.) |
Carbon Group | Group 4A elements. They are also known as crystallogens (Carbon, Silicon, Tin, Lead, etc.) |
Pnictogens | Group 5A elements. This group is also called the nitrogen family (Nitrogen, Phosphorus, Arsenic, etc.) |
Chalcogens | Group 6A elements. This group is also called the oxygen family (Oxygen, Sulfur, Selenium, etc.) |
Halogens | Group 7A elements. They react with metals to form salts (Fluorine, Chlorine, Iodine, etc.) |
Noble Gases | Group 8A elements. They are very unreactive, or inert (Neon, Argon, Krypton, etc.) |
Atomic Mass (Atomic Weight) | Average mass - in amu - of a particular element based on the relative abundance of the various isotopes. Numerically equivalent to the mass in grams of one mole of the element |
Mass Spectrometry | Technique that separates particles by their mass. It is used in determining the precise masses and relative abundance of isotopes in a given sample |
Avogadro's Number | 6.022 × 10^23 particles; number of particles in one mole |
Molar Mass | Mass of one mole of atoms of an element. Equal to the atomic mass in atomic mass units |
Chemical Formula | Symbolic representation of a compound, indicating the elements present in the compound and the relative number of atoms of each element |
Empirical Formula | Chemical formula that gives the relative number of atoms of each element in a compound |
Molecular Formula | Chemical formula that gives the actual number of atoms of each element in a compound |
Structural Formula | Chemical formula that uses lines to represent chemical bonds |
Ball-and-Stick Model | Molecular model that represents atoms as ball and chemical bonds as sticks |
Space-Filling Model | Molecular model where atoms fill the space between each other and are scaled by size |
Atomic Elements | Elements that exist in nature with single atoms as their basic units |
Molecular Elements | Elements that exist in nature with molecules as their basic units |
Diatomic Molecules | Molecules composed of two atoms |
Polyatomic Molecules | Molecules composed of three or more atoms |
Formula Unit | Smallest, electrically neutral collection of ions in an ionic compound, such as NaCl for table salt |
Polyatomic Ion | Ion composed of two or more atoms |
Common Names | Nicknames for compounds that give little to not information about the chemical structure of the compound |
Systematic Names | Official names for compounds that describe the chemical composition |
Binary Compounds | Compounds that contain only two different elements |
Oxyanions | Anions containing oxygen and another element |
Hydrates | Ionic compounds containing a specific number of water molecules for each formula unit |
Formula Mass | Average mass of a molecule in a compound. Synonymous with molecular mass and atomic mass |
Mass Percent Composition | Element's percentage of the total mass of a compound containing the element |
Combustion Analysis | Method for obtaining empirical formulas for unknown compounds, especially those containing carbon and hydrogen, by burning a sample of the compound in pure oxygen and analyzing the products |
Chemical Reaction | Process in which one or more substances are converted into one or more different ones |
Chemical Equation | Symbolic representation of a chemical reaction |
Reactants | Substances on the left side of a chemical equation |
Products | Substances on the right side of a chemical equation |
Stoichiometry | Numerical relationships between reactants and products in a balanced chemical equation |
Limiting Reactant | Reactant that has the smallest stoichiometric amount in a reactant mixture. Consequently, this limits the amount of product in a chemical reaction |
Excess Reactant | Reactant that is not the limiting reactant |
Theoretical Yield | Greatest possible amount of product that can be made in a chemical reaction |
Actual Yield | Amount of product actually produced by a chemical reaction |
Percent Yield | Percentage of the theoretical yield of a chemical reaction that is actually produced |
Synthesis Reaction | Reaction where two reactants combine into one product |
Decomposition Reaction | Reaction where one reactant breaks down into multiple products |
Single Replacement Reaction | Reaction where one uncombined reactant replaces another in a product compound |
Double Replacement Reaction | Reaction where the anions and cations of two reactant compounds switch places and form two entirely new compounds |
Combustion Reaction | Reaction where a substance combines with oxygen to form one or more oxygen-containing compounds and emits heat. These reactions are necessary for engines to function. |
Solution | Homogenous mixture of two substances |
Solvent | Majority component of a solution; the dissolving component |
Solute | Minority component of a solution; the dissolved component |
Aqueous Solution | Solution where water is the solvent |
Concentrated Solution | Solution that contains a large amount of solute relative to the amount of solvent |
Dilute Solution | Solution that contains a small amount of solute relative to the solvent |
Stock Solution | Highly concentrated form of a solution used in laboratories to make less concentrated solutions |
Solubility | Amount of a substance that will dissolve in a given amount of solvent |
Miscibility | Ability of two or more substances to fully dissolve in each other at any concentration |
Molarity (M) | Amount of solute in moles divided by the volume of the solution in liters |
Electrolyte | Substance that dissolves in water to form solutions to conduct electricity |
Strong Electrolyte | Substance that completely dissociates into ions when dissolved in water |
Weak Electrolyte | Substance that partially dissociates into ions when dissolved in water |
Nonelectrolyte | Substance that does not dissociate into ions when dissolved in water |
Soluble | Being able to dissolve to a significant extent in water |
Insoluble | Being unable to dissolve to a significant extent in water |
Precipitation Reaction | Reaction where a solid forms when two solutions are mixed |
Precipitate | Solid that forms in a precipitation reaction |
Molecular Equation | Equation showing the complete neutral formula for each compound in a reaction |
Complete Ionic Equation | Equation that lists individually all of the ions present as reactants or products in a chemical reaction |
Net Ionic Equation | Equation that shows only the species that actually change during a chemical reaction |
Spectator Ion | Ion that does not participate in a reaction and therefore remains in solution |
Enthalpy of Solution | Enthalpy change associated with the formation of a solution |
Heat of Hydration | Enthalpy change that occurs when one mole of gaseous solute ions is dissolved in water |
Saturated Solution | Solution that contains the exact equilibrium amount of solute |
Unsaturated Solution | Solution containing less than the equilibrium amount of solute |
Supersaturated Solution | Unstable solution in which more than the equilibrium amount of solute id dissolved |
Recrystallization | Technique used to purify solids in which the solid is put into hot solvent until the solution is saturated. When the solution cools, the purified solute comes out of solution |
Henry's Law | Solubility of a gas equals the partial pressure of the gas times a constant of proportionality |
Molality (m) | Solution concentration expressed as the number of moles of solute per kilogram of solvent |
Parts by Mass | Mass of the solute divided by mass of the solution times a multiplication factor |
Percent by Mass | Method of expressing parts by mass that used a multiplication factor of one hundred percent |
Parts Per Million (ppm) | Method of expressing parts by mass that uses a multiplication factor of 10^6 |
Parts Per Billion (ppb) | Method of expressing parts by mass that uses a multiplication factor of 10^9 |
Parts by Volume | Volume of the solute divided by volume of the solution times a multiplication factor |
Mole Percent | Mole fraction multiplied by one hundred percent |
Colligative Property | Property that depends on the amount of a solute, but not the solute's identity |
Raoult's Law | Vapor pressure of a solution equals the mole fraction of the solvent times the vapor pressure of the pure solvent at the same pressure |
Vapor Pressure Lowering | Change in vapor pressure that occurs in pure substances upon adding a solute |
Ideal Solution | Solution that follows Raoult's Law at all concentrations for both solute and solvent |
Freezing Point Depression | When a solute causes a solution to have a lower melting point than the pure solvent |
Boiling Point Elevation | When a solute causes a solution to have a higher boiling point than the pure solvent |
Osmosis | Flow of solvent from a solution of lower concentration to one of higher solute concentration |
Semipermeable Membrane | Membrane that allows some substances to mass through, but not others |
Osmotic Pressure | Pressure required to stop osmotic flow |
Van't Hoff Factor (i) | Ratio of moles of particles in a solution to moles of formula units dissolved |
Colloid (Colloidal Dispersion) | Mixture in which a dispersed substance (similar to a solute) is finely divided but not truly dissolved in a dispersing medium. These mixtures are often opaque and hazy |
Aerosol | Colloid where a liquid or solid is dispersed within a gas |
Foam | Colloid where a gas is dispersed within a liquid |
Emulsion | Colloid where a liquid is dispersed within another liquid |
Tyndall Effect | Scattering of light by a colloidal dispersion |
Acid | Molecular compound that produces H+ ions in aqueous solution. They have a pH below seven, taste sour, and turn blue litmus red |
Binary Acid | Acid composed of hydrogen and a nonmetal; an example includes hydrochloric acid |
Oxyacid | Acid composed of hydrogen and an oxyanion |
Strong Acid | Acid that completely dissociates in solution |
Weak Acid | Acid that partially dissociates in solution |
Base | Molecular compound that produces OH- ions in aqueous solution. They have a pH above seven, taste bitter, and turn red litmus blue |
Strong Base | Base that completely dissociates in solution |
Weak Base | Base that partially dissociates in solution |
Amphoteric | When a molecule or ion can act as both an acid and a base |
Neutralization Reaction | Reaction where an acid and a base neutralize each other, producing water and a salt |
Hydronium Ion | H3O+ ion; formed from the association of water an an H+ ion donated by an acid |
Salt | Ionic compound formed in a neutralization reaction by the replacement of an H+ ion from the acid with a cation from the base |
Titration | Laboratory procedure in which a substance in a solution of known concentration is reacted with another substance in a solution of unknown concentration in order to determine the unknown concentration |
Equivalence Point | Point in titration at which the added solute reacts completely with the solute present in solution |
Indicator | Dye whose color depends on the acidity or basicity of the solution |
Endpoint | Point of pH change where an indicator changes color |
Gas-Evolution Reaction | Reaction in which two aqueous solutions mix and a gas forms, causing bubbling |
Redox Reaction | Reaction in which electrons transfer from one reactant to another |
Oxidation | Loss of electrons, producing a more positive charge |
Reduction | Gain of electrons, producing a more negative charge |
Oxidation Number | Positive or negative whole number that represents the "charge" an atom in a compound would have if all shared electrons were assigned to the atom with a greater attraction for those electrons |
Oxidizing Agent | Substance that causes the oxidation of another substance in reaction; this is reduced in a redox reaction |
Reducing Agent | Substance that causes the reduction of another substance in reaction; this is oxidized in reaction |
Activity Series | Listing of metals in order of decreasing ability to oxidize and decreasing tendency to lose electrons |
Alkaloids | Organic bases found in plants. They are often poison |
Arrhenius Definition | Acids produce H+ ions in aqueous solution; bases produce OH- in aqueous solution |
Bronsted-Lowry Definition | Acids donate protons in aqueous solution; bases accept protons in aqueous solution |
Conjugate Acid-Base Pair | Two substances related to each other by the transfer of a proton |
Conjugate Acid | Any base to which a proton has been added |
Conjugate Base | Any acid from which a proton has been removed |
Monoprotic Acid | Acid that contains one ionizable proton |
Diprotic Acid | Acid that contains two ionizable protons |
Triprotic Acid | Acid that contains three ionizable protons |
Polyprotic Acid | Acid that contains more than three ionizable protons |
Acid Ionization Constant | Equilibrium constant for the ionization reaction of a weak acid. It is used to compare the relative strengths of weak acids, and is symbolized by "K" with a subscript "a." |
Autoionization | Process by which water acts as an acid and a base with itself |
Ion Product Constant for Water | Equilibrium constant for the autoionization of water. Sometimes called the dissociation constant for water. It is symbolized by "K" with a subscript "w." |
Neutral Solution | Solution with equal concentrations of the hydronium and hydroxide ions |
Acidic Solution | Solution with a greater concentration of the hydronium ion compared to the hydroxide ion |
Basic Solution | Solution with a greater concentration of the hydroxide ion compared to the hydronium ion |
pH | Negative logarithm of the concentration of the hydronium ion in a solution. It defines acidity |
pOH | Negative logarithm of the concentration of the hydroxide ion in a solution. It defines basicity |
Percent Ionization | Ratio of the ionized acid concentration to the initial acid concentration, times one hundred percent |
Base Ionization Constant | Equilibrium constant for the ionization reaction of a weak base. It is used to compare the relative strengths of weak acids, and is symbolized by "K" with a subscript "b." |
Lewis Acid | Atom, ion, or molecule that is an electron pair acceptor |
Lewis Base | Atom, ion, or molecule that is an electron pair donor |
Acid Rain | Precipitation with a low pH, created by sulfuric and nitric acid |
Buffer | Solution that resists pH change by neutralizing acid or base |
Common Ion Effect | Tendency for a common ion to decrease the solubility of an ionic compound or to decrease the ionization of a weak acid or a weak base |
Buffer Capacity | Amount of acid or base that can be added to a buffer without causing a large change in pH |
Solubility Product Constant | Equilibrium expression for a chemical equation that represents the dissolution of an ionic compound. Symbolized by "K" with the subscript "sp." |
Selective Precipitation | Process involving the addition of a reagent to a solution that forms a precipitate with one of the dissolved ions but not the other |
Inert | Describes an unreactive element, such as a noble gas, that rarely bonds with other elements |
Pressure | Amount of force per unit of area |
Barometer | Instrument that measures air pressure |
Manometer | Instrument that measures pressure of a gaseous sample |
Millimeter of Mercury (mmHG) | Unit of pressure referring to the air pressure required to push a column of mercury to a height of one millimeter in a barometer. One atmosphere equals seven hundred and sixty of these |
Torr | Alternative name for the unit of pressure mmHG. |
Atmosphere (atm) | Unit of pressure relative to the average pressure at sea level; atmospheric pressure at sea level equals one of these units |
Pascal (Pa) | Unit of pressure equal to one newton per square meter. It is the SI unit of pressure |
Pounds per Square Inch (psi) | Unit of pressure, where atmospheric pressure equals 14.7 at sea level |
Boyle's Law | Volume and pressure are inversely proportional |
Charles's Law | Volume and temperature are directly proportional |
Gay-Lussac's Law | Pressure and temperature are directly proportional |
Avogadro's Law | Volume and amount of substance (in moles) are directly proportional |
Ideal Gas Law | Law that combines Boyle's, Charles's, Avogadro's, and Gay Lussac's Law into one comprehensive equation: PV = nRT. P is pressure, V is volume, T is temperature, R is a constant, and n is moles of gas |
Ideal Gas | Hypothetical gas that perfectly follows the ideal gas law under all conditions |
Ideal Gas Constant | Variable "R" in the ideal gas equation. It equals 0.08206 when pressure is measured in atmospheres |
Molar Volume | Volume occupied by one mole of a substance |
STP | Standard Temperature and Pressure. Equal to 273 K (or 0° C) and 1.00 atm |
Partial Pressure | Pressure due to any individual component of a gas mixture |
Dalton's Law of Partial Pressures | Sum of the partial pressures of the components in a gaseous mixture must always equal the total pressure exerted by the gaseous mixture |
Hypoxia | Abnormally low levels of blood oxygen. Causes dizziness, headaches, shortness of breath, and eventually death |
Oxygen Toxicity | Abnormally high levels of blood oxygen. Causes muscle twitching, tunnel visions, and convulsions |
Nitrogen Narcosis | Increased partial pressure of nitrogen in the bloodstream, resulting in symptoms similar to those of intoxication. Also known as "rapture of the deep" or the "Martini effect" |
Decompression Sickness | When dissolved gases come out of solution and become bubbles inside the body due to depressurization. Also known as "the bends" or "divers' disease." |
Vapor Pressure | Partial pressure of a vapor in dynamic equilibrium with its liquid |
Kinetic Molecular Theory | Model of an ideal gas as a collection of point particles in constant motion undergoing completely elastic collisions |
Mean Free Path | Average distance that a molecule in a gas travels between collisions |
Diffusion | Process by which gas molecules spread out in response to a concentration gradient |
Effusion | Process by which molecules escape a container into a vacuum through a small hole |
Graham's Law | Ratio of effusion rates between two gases is equal to the square roots of the inverse of the molar masses |
Van der Waals Equation | Extrapolation of the ideal gas law that considers the effects of intermolecular forces and particle volume in a nonideal gas |
Exothermic Reaction | Reaction that gives off heat into its surroundings (negative change in enthalpy) |
Endothermic Reaction | Reaction that absorbs heat from its surroundings (positive change in enthalpy) |
Work | Action of a force across a distance |
Energy | Capacity to do work |
Kinetic Energy | Energy associated with an object's motion |
Potential Energy | Energy associated with an object's position or composition |
Thermal Energy | Energy associated with an object's temperature |
Chemical Energy | Energy associated with an object's electrons and bonds |
Law of Conservation of Energy | Energy is neither created nor destroyed during a chemical reaction |
System | Portion of the universe that is singled out for investigation |
Surroundings | Everything in the universe that exits outside the system under investigation |
Joule (J) | SI unit of energy. Equal to kg × m^2/s^2 |
Calorie (cal) | Unit of energy defined as the amount of energy required to raise the temperature of one gram of water by one Celsius degree. Equal to 4.184 Joules |
Calorie (Cal) | Unit of energy equal to one thousand lowercase "c" calories. Also called the kilocalorie (kcal) |
Kilowatt-Hour (kWh) | Unit of energy used to express large amounts of energy produced by the flow of electricity. Often used by power companies to determine electrical usage. Equal to 3.60 × 19^6 J |
Thermodynamics | General study of energy and its conversion |
Internal Energy (E) | Sum of the kinetic and potential energies of all of the particles that compose a system |
State Function | Function whose value depends only on the state of the system, not how the system got to that state |
Heat | Energy in transfer to or from a thermodynamic system |
Thermal Equilibrium | State of no additional net transfer of heat |
Heat Capacity (C) | Quantity of heat required to change a system's temperature by one Celsius degree |
Specific Heat Capacity | Amount of heat required to heat one gram of a substance by one Celsius degree |
Molar Heat Capacity | Amount of heat required to heat one mole of a substance by one Celsius degree |
Pressure-Volume Work | Work that occurs when a volume change takes place against an external pressure |
Calorimetry | Experimental procedure used to measure the heat that evolves in a chemical reaction |
Bomb Calorimeter | Device designed to measure the change in internal energy for combustion reactions |
Enthalpy (H) | Sum of the internal energy of a system and the product of its pressure and volume |
Enthalpy of Reaction (Heat of Reaction) | Enthalpy change for a chemical reaction |
Coffee-Cup Calorimeter | Device used to measure enthalpy of reaction for aqueous solutions |
Hess's Law | If a chemical equation can be expressed as the sum of a series of steps, then the heat of reaction for the overall equation is the sum of the heats of reactions for each step |
Standard Enthalpy Change | Change in enthalpy for a process where all reactants and products are at standard state |
Standard Enthalpy (Heat) of Formation | Change in enthalpy when one mole of a compound forms from its constituent elements in their standard states |
Standard State | Reference point of a material or substance used to calculate its properties under different conditions |
Quantum-Mechanical Model | Model that explains behavior of microscopic particles like electrons and protons |
Electromagnetic Radiation | Energy embodied in oscillating electric and magnetic fields |
Amplitude | Vertical height of a wave's crest (or depth of its trough) |
Wavelength (λ) | Distance between adjacent crests or analogous points on a wave. Represented by a lambda |
Frequency (v) | Number of cycles that pass through a stationary point in a given time period. Measured in Hertz |
Electromagnetic Spectrum | Range of the wavelengths of all possible electromagnetic radiation |
Gamma Radiation (γ) | Form or electromagnetic radiation with the shortest wavelength |
X-Rays | Form of electromagnetic radiation with wavelengths longer than those of gamma rays; used in medical imaging |
Ultraviolet Radiation (UV) | Form of electromagnetic radiation with wavelengths shorter than visible light |
Visible Light | Form of electromagnetic radiation that can be detected by the human eye |
Infrared Radiation (IR) | Form of electromagnetic radiation with longer wavelengths than visible light |
Microwaves | Form of electromagnetic radiation with wavelengths slightly longer than infrared radiation |
Radio Waves | Form of electromagnetic radiation with the longest wavelengths |
Interference | Superposition of two or more waves in overlapping space, resulting in their interaction |
Constructive Interference | Interference resulting in an increase in amplitude |
Destructive Interference | Interference resulting in a decrease in amplitude |
Diffraction | When a wave, emerging from an aperture or coming around a corner, spreads out to form a new front |
Photoelectric Effect | Observation that many metals emit electrons when light falls upon them |
Photon (Quantum) | Smallest possible packet of electromagnetic radiation |
Emission Spectrum | Range of wavelengths emitted by a particular substance |
Absorption Spectrum | Range of wavelengths absorbed by a particular substance |
De Broglie Relation | Observation that the wavelength of a particle is inversely proportional to its momentum |
Heisenberg's Uncertainty Principle | Principle stating that due to the wave-particle duality, it is fundamentally impossible to precisely determine both the position and momentum of a particle at a given time |
Deterministic | Characteristic of classical motion; implies that present circumstances determine future events |
Indeterminacy | Principle asserting that present circumstances do not necessarily determine future events in the quantum-mechanical realm |
Orbital | Probability distribution map, based on the quantum-mechanical model of the atom, used to describe the likely position of an electron in an atom; also, an allowed energy state for an electron |
Wave Function | Mathematical function that describes the wavelike nature of the electron |
Quantum Numbers | One of four interrelated numbers that determine the shape and energy of orbitals |
Principal Quantum Number (n) | Integer that specifies the overall size and energy of an orbital. The higher this number, the greater the average distance between the electron and the nucleus and the higher its energy |
Angular Momentum Quantum Number (l) | Integer that determines the overall shape of an orbital |
Magnetic Quantum Number (ml) | Integer that specifies the orientation of an orbital |
Spin Quantum Number (s) | Integer that denotes the electrons spin (1/2 or -1/2) |
Principal Level (Principal Shell) | Group of orbitals with the same principal quantum number |
Sublevel (Subshell) | Orbitals in the same principal level with the same principal and angular momentum quantum numbers |
Probability Density | Probability of finding an electron at a point in space, expressed by a three-dimensional plot of the wave function squared |
Radial Distribution Function | Mathematical function - corresponding to a specific orbital - that represents the total probability of finding an electron within a thin spherical shell at a distance of "r" |
Node | Point where the probability density and radial distribution function both pass through zero; for a wave, points where the amplitude is zero |
Phase | Sign of the amplitude of the wave; positive or negative |
Periodic Property | Property of an element that is predictable based on its position in the periodic t able |
Electron Configuration | Notation that shows the particular orbitals that are occupied by electrons in an atom |
Ground State | Lowest energy state in an atom, ion, or molecule |
Pauli Exclusion Principle | No two electrons in an atom can have the same four quantum numbers |
Degenerate Orbitals | Orbitals with the same principal quantum number that have the same energy |
Coulomb's Law | The potential energy between two charged particles is proportional to the product of the charges divided by the square of the distance that separates the charges |
Shielding | Repulsive effect on an electron by other electrons in lower-energy orbitals that screen it from the full effects of the attractive forces of the nucleus |
Effective Nuclear Charge | Actual nuclear charge experienced by an electron, defined as the charge of the nucleus plus the charge of the shielding electrons |
Penetration | Phenomenon of some higher-level atomic orbitals having significant amounts of probability within the space occupied by orbitals of lower energy levels |
Aufbau Principle | Principle that indicates the pattern of orbital filling in an atom |
Hund's Rule | When electrons fill degenerate orbitals, they first fill them singly with parallel spins |
Valence Electrons | Electrons in the outermost principal energy level |
Core Electrons | Electrons that are not in the valence shell |
Atomic Radius | Average bonding radius of an atom; this increases as you move down a column and decreases as you move to the right in a row |
Covalent Radius | |
Van der Waals Radius | |
Paramagnetic | |
Diamagnetic | |
Ionization Energy | |
Electron Affinity | |
Metallic Character | |
Chemical Bond | |
Ionic Bond | |
Ionic Compound | |
Covalent Bond | |
Molecular Compound | |
Metallic Bond | |
Lewis Model | |
Octet | |
Duet | |
Octet Rule | |
Lattice Energy | |
Born-Haber Cycle | |
Bonding Pair | |
Lone Pair (Nonbonding Electrons) | |
Single Bond | |
Double Bond | |
Triple Bond | |
Polar Covalent Bond | |
Nonpolar Covalent Bond | |
Electronegativity | |
Dipole Moment | |
Percent Ionic Character | |
Resonance Structure | |
Resonance Hybrid | |
Formal Charge | |
Free Radical | |
Incomplete Octet | |
Expanded Octet | |
Bond Energy | |
Bond Length | |
VSEPR (Valence Shell Electron Pair Repulsion) Theory | |
Electron Groups | |
Molecular Geometry | |
Linear Geometry | |
Trigonal Planar Geometry | |
Tetrahedral Geometry | |
Trigonal Bipyramidal Geometry | |
Octahedral Geometry | |
Electron Geometry | |
Trigonal Pyramidal Geometry | |
Bent Geometry | |
Seesaw Geometry | |
T-Shaped Geometry | |
Square Pyramidal Geometry | |
Square Planar Geometry | |
Valence Bond Theory | |
Hybridization | |
Hybrid Orbitals | |
Pi (π) Bond | |
Sigma (σ) Bond | |
Molecular Orbital Theory | |
Bonding Orbital | |
Antibonding Orbital | |
Bond Order | |
Nonbonding Orbital | |
Crystalline | |
Amorphous | |
Intermolecular Force | |
Dispersion Force (London Force) | |
Dipole-Dipole Force | |
permanent Dipole | |
Hydrogen Bond | |
Ion-Dipole Force | |
Surface Tension | |
Viscosity | |
Capillary Action | |
Vaporization | |
Condensation | |
Volatile | |
Nonvolatile | |
Heat of Vaporization | |
Vapor Pressure | |
Boiling Point | |
Normal Boiling Point | |
Critical Temperature | |
Critical Pressure | |
Sublimation | |
Deposition | |
Melting (Fusion) | |
Freezing | |
Melting Point | |
Heat of Fusion | |
Heat of Sublimation | |
Phase Diagram | |
Triple Point | |
Critical Point | |
Graphene | |
X-Ray Diffraction | |
X-Ray Crystallography | |
Crystalline Lattice | |
Unit Cell | |
Simple Cubic | |
Body-Centered Cubic | |
Face-Centered Cubic | |
Coordination Number | |
Packing Efficiency | |
Hexagonal Closest Packing | |
Molecular Solids | |
Ionic Solids | |
Atomic Solids | |
Nonbonding Atomic Solids | |
Metallic Atomic Solids | |
Network Covalent Solids | |
Polymorphs | |
Graphite | |
Diamond | |
Fullerenes | |
Nanotubes | |
Silicates | |
Quartz | |
Ceramics | |
Clay | |
Portland Cement | |
Concrete | |
Glass | |
Vitreous Silica (Fused Silica) | |
Soda-Lime Glass | |
Borosilicate Glass (Pyrex) | |
Leaded Glass | |
Band Theory | |
Valence Band | |
Conduction Band | |
Band Gap | |
Semiconductor | |
N-Type Semiconductor | |
P-Type Semiconductor | |
P-N Junction | |
Diode | |
Polymer | |
Monomer | |
Addition Polymer | |
Condensation Polymer | |
Dimer | |
Rate Law | |
Rate Constant | |
Reaction Order (n) | |
Overall Order | |
Integrated Rate Law | |
Half Life (Reaction) | |
Arrhenius Equation | |
Activation Energy | |
Frequency Factor | |
Activated Complex (Transition State) | |
Exponential Factor | |
Collision Model | |
Orientation Factor | |
Collision Frequency | |
Reaction Mechanism | |
Elementary Step | |
Reaction Intermediate | |
Molecularity | |
Unimolecular | |
Bimolecular | |
Termolecular | |
Rate-Determining Step | |
Catalyst | |
Homogenous Catalysis | |
Heterogenous Catalysis | |
Enzyme | |
Active Site | |
Substrate | |
Reversible | |
Dynamic Equilibrium | |
Equilibrium Constant | |
Law of Mass Action | |
Reaction Quotient | |
Le Chatelier's Principle |