| Term | Definition |
|---|---|
| atomic mass units | A unit of mass used to express the mass of individual atoms or molecules, where one amu is defined relative to carbon-12. |
| Avogadro's number | The constant 6.022 × 10^23 mol^-1 that represents the number of particles (atoms, molecules, or formula units) in one mole of a substance. |
| constituent particles | The individual atoms, molecules, or ions that make up a substance. |
| dimensional analysis | A mathematical technique for converting between different units of measurement by using conversion factors and canceling units. |
| formula unit | The smallest unit of a compound that shows the fixed proportions of atoms or ions held together. |
| molar mass | The mass in grams of one mole of a substance, numerically equal to the average mass of one particle in atomic mass units. |
| mole concept | A fundamental chemistry concept that relates the number of particles (atoms, molecules, or ions) to measurable quantities through Avogadro's number. |
| Term | Definition |
|---|---|
| average atomic mass | The weighted average of the masses of all isotopes of an element, based on their relative abundances in nature. |
| isotopes | Atoms of the same element that have different numbers of neutrons and therefore different mass numbers. |
| isotopic masses | The mass of individual isotopes of an element, typically expressed in atomic mass units. |
| mass spectrum | A graphical representation showing the masses of isotopes of an element and their relative abundances. |
| relative abundance | The percentage or proportion of each isotope present in a naturally occurring sample of an element. |
| weighted average | A calculation method that accounts for the relative abundance of each isotope when determining the average atomic mass of an element. |
| Term | Definition |
|---|---|
| constituent elements | The individual elements that make up a compound in fixed proportions. |
| elemental composition by mass | The percentage or proportion of each element present in a substance, expressed as a mass fraction or mass percentage. |
| empirical formula | The chemical formula that represents the lowest whole number ratio of atoms of the elements in a compound. |
| formula unit | The smallest unit of a compound that shows the fixed proportions of atoms or ions held together. |
| law of definite proportions | The principle that the ratio of the masses of the constituent elements in any pure sample of a compound is always the same. |
| pure substance | A material with a fixed, definite composition and consistent properties throughout. |
| Term | Definition |
|---|---|
| elemental analysis | An analytical technique used to determine the relative numbers of atoms of each element in a substance and to assess its purity. |
| elemental composition by mass | The percentage or proportion of each element present in a substance, expressed as a mass fraction or mass percentage. |
| mixture | Materials that contain atoms, molecules, or formula units of two or more types, whose relative proportions can vary. |
| pure substance | A material with a fixed, definite composition and consistent properties throughout. |
| purity | The degree to which a substance contains only one type of atom, molecule, or formula unit without contamination from other substances. |
| Term | Definition |
|---|---|
| Aufbau principle | The rule that electrons fill orbitals in order of increasing energy, with lower energy orbitals filled before higher energy orbitals. |
| core electrons | Inner electrons in an atom that are not in the outermost shell and do not participate in bonding. |
| Coulomb's law | The principle that the electrostatic force between charged particles is proportional to the product of their charges and inversely proportional to the square of the distance between them. |
| effective charge | The net positive charge experienced by an electron in an atom, accounting for shielding by inner electrons. |
| electrons | Negatively charged subatomic particles that orbit the nucleus of an atom. |
| ground-state electron configuration | The arrangement of electrons in an atom or ion in its lowest energy state, following the Aufbau principle. |
| ionization energy | The energy required to remove an electron from an atom in the gas phase. |
| neutrons | Neutral subatomic particles found in the nucleus of an atom. |
| nucleus | The positively charged center of an atom composed of protons and neutrons. |
| protons | Positively charged subatomic particles found in the nucleus of an atom. |
| shell | Energy levels in an atom that contain electrons, designated by principal quantum numbers (n = 1, 2, 3, etc.). |
| shielding | The reduction in the effective nuclear charge experienced by outer electrons due to repulsion from inner electrons. |
| subshell | A subdivision of an electron shell characterized by a specific orbital type (s, p, d, or f) and containing orbitals of similar energy. |
| valence electrons | Electrons in the outermost shell of an atom that participate in bonding and determine many properties of substances. |
| Term | Definition |
|---|---|
| electron configuration | The arrangement of electrons in an atom or ion, describing which orbitals and subshells are occupied and how many electrons are in each. |
| ionization energy | The energy required to remove an electron from an atom in the gas phase. |
| photoelectron spectroscopy | An experimental technique that measures the energy required to remove electrons from different subshells of an atom or ion. |
| photoelectron spectrum | A graphical representation of data from photoelectron spectroscopy showing peaks that correspond to electrons in different subshells of an atom or ion. |
| subshell | A subdivision of an electron shell characterized by a specific orbital type (s, p, d, or f) and containing orbitals of similar energy. |
| Term | Definition |
|---|---|
| atomic properties | Characteristics of atoms such as size, ionization energy, electron affinity, and electronegativity that vary predictably across the periodic table. |
| atomic radius | The size of an atom, typically measured as the distance from the nucleus to the outermost electrons. |
| Coulomb's law | The principle that the electrostatic force between charged particles is proportional to the product of their charges and inversely proportional to the square of the distance between them. |
| effective nuclear charge | The net positive charge experienced by an electron in an atom, accounting for shielding by inner electrons. |
| electron affinity | The energy change that occurs when an electron is added to an atom in the gas phase. |
| electron configuration | The arrangement of electrons in an atom or ion, describing which orbitals and subshells are occupied and how many electrons are in each. |
| electronegativity | A measure of an atom's ability to attract valence electrons in a chemical bond; increases across a period and decreases down a group in the periodic table. |
| electronic structure | The arrangement of electrons in an atom, including the distribution across shells and subshells. |
| ionic radius | The size of an ion, which differs from the neutral atom due to the gain or loss of electrons. |
| ionization energy | The energy required to remove an electron from an atom in the gas phase. |
| periodicity | The recurring pattern of properties in elements that repeats across periods and groups in the periodic table. |
| shell | Energy levels in an atom that contain electrons, designated by principal quantum numbers (n = 1, 2, 3, etc.). |
| shell model | A model of atomic structure in which electrons occupy discrete energy levels or shells around the nucleus. |
| shielding | The reduction in the effective nuclear charge experienced by outer electrons due to repulsion from inner electrons. |
| subshell | A subdivision of an electron shell characterized by a specific orbital type (s, p, d, or f) and containing orbitals of similar energy. |
| unpaired electrons | Electrons that occupy orbitals alone rather than in pairs, affecting an atom's magnetic and chemical properties. |
| Term | Definition |
|---|---|
| chemical bond | An attractive force between atoms that holds them together in a compound. |
| ionic charge | The net electrical charge of an ion, determined by the number of valence electrons and the element's position on the periodic table. |
| ionic compound | Compounds formed by the electrostatic attraction between positively charged cations and negatively charged anions. |
| periodic table | A systematic arrangement of elements organized by atomic number and grouped by similar chemical properties. |
| periodicity | The recurring pattern of properties in elements that repeats across periods and groups in the periodic table. |
| reactivity | The tendency of an element to undergo chemical reactions and form bonds with other elements. |
| valence electrons | Electrons in the outermost shell of an atom that participate in bonding and determine many properties of substances. |
| Term | Definition |
|---|---|
| bond dipole | The separation of partial positive and negative charges in a polar bond; greater electronegativity differences lead to greater bond dipoles. |
| covalent bond | A chemical bond typically formed between two nonmetals where valence electrons are shared between atoms. |
| delocalized electrons | Valence electrons in a metallic solid that are not associated with any individual atom but are distributed throughout the structure. |
| electronegativity | A measure of an atom's ability to attract valence electrons in a chemical bond; increases across a period and decreases down a group in the periodic table. |
| ionic bond | A chemical bond typically formed between a metal and nonmetal where electrons are transferred from one atom to another. |
| ionic character | The degree to which a bond exhibits properties of an ionic bond; all polar bonds possess some ionic character. |
| metallic solid | A solid composed of metal atoms where valence electrons are delocalized and not associated with any individual atom. |
| nonpolar covalent bond | A covalent bond between atoms of similar electronegativity where valence electrons are shared relatively equally. |
| partial negative charge | The negative charge that develops on the more electronegative atom in a polar covalent bond. |
| polar covalent bond | A covalent bond between atoms of unequal electronegativity where valence electrons are shared unequally, resulting in partial charges on the atoms. |
| valence electrons | Electrons in the outermost shell of an atom that participate in bonding and determine many properties of substances. |
| Term | Definition |
|---|---|
| anion | A negatively charged ion formed when an atom gains one or more electrons. |
| bond energy | The average energy required to break a chemical bond between two atoms. |
| bond length | The distance between the nuclei of two bonded atoms, which is affected by bond order and atomic radius. |
| bond order | The number of electron pairs shared between two atoms in a chemical bond, which affects bond energy and bond length. |
| cation | A positively charged ion formed when an atom loses one or more electrons. |
| Coulomb's law | The principle that the electrostatic force between charged particles is proportional to the product of their charges and inversely proportional to the square of the distance between them. |
| covalent bond | A chemical bond typically formed between two nonmetals where valence electrons are shared between atoms. |
| equilibrium bond length | The separation between atoms at which the potential energy is at its lowest point, representing the most stable bond distance. |
| internuclear distance | The distance between the nuclei of two atoms, which influences the strength of the interaction between them. |
| ionic interaction | The electrostatic attraction between cations and anions, whose strength depends on the charges of the ions and the distance between them. |
| potential energy | The stored energy in chemical bonds and molecular structures that can be released or absorbed during a reaction. |
| Term | Definition |
|---|---|
| anion | A negatively charged ion formed when an atom gains one or more electrons. |
| attractive forces | Electrostatic forces between oppositely charged ions that hold them together in an ionic solid. |
| cation | A positively charged ion formed when an atom loses one or more electrons. |
| Coulomb's law | The principle that the electrostatic force between charged particles is proportional to the product of their charges and inversely proportional to the square of the distance between them. |
| ionic crystal | A solid structure in which cations and anions are arranged in a repeating three-dimensional pattern. |
| ionic solid | A crystalline compound composed of cations and anions held together by electrostatic forces. |
| particulate model | A representation of matter showing individual atoms, molecules, or ions and their interactions to describe chemical processes at the molecular level. |
| repulsive forces | Electrostatic forces between ions of the same charge that push them apart in an ionic solid. |
| Term | Definition |
|---|---|
| delocalized valence electrons | Valence electrons in a metal that are not bound to specific atoms but move freely throughout the entire metallic structure, often described as a 'sea of electrons'. |
| interstitial alloy | An alloy in which smaller atoms occupy the spaces between larger atoms in the crystal lattice, making the structure more rigid and decreasing malleability and ductility. |
| interstitial spaces | The gaps or voids between atoms in a crystal lattice where smaller atoms can fit in an interstitial alloy. |
| lattice | The regular, repeating three-dimensional arrangement of atoms or ions in a crystalline solid. |
| metallic bonding | The type of chemical bonding in metals where valence electrons are delocalized throughout the structure, creating a flexible network of positive ions held together by a mobile electron sea. |
| sea of electrons | A model representing the mobile, delocalized valence electrons that surround positive metal ions in a metallic solid. |
| substitutional alloy | An alloy formed when atoms of comparable size replace or substitute for atoms in the original crystal lattice structure. |
| Term | Definition |
|---|---|
| Lewis diagram | A structural representation of a molecule showing the arrangement of valence electrons as dots and bonds between atoms. |
| molecule | A group of atoms bonded together, representing the smallest fundamental unit of a chemical compound. |
| Term | Definition |
|---|---|
| equivalent structures | Multiple Lewis diagrams of the same molecule that have identical connectivity and differ only in electron placement, contributing equally to the actual structure. |
| formal charge | A calculation used to determine the charge on an individual atom in a molecule, calculated as the number of valence electrons minus the number of non-bonding electrons minus half the number of bonding electrons. |
| Lewis diagram | A structural representation of a molecule showing the arrangement of valence electrons as dots and bonds between atoms. |
| nonequivalent structures | Multiple possible Lewis diagrams of a molecule that differ in connectivity or atom arrangement, with formal charge used to determine which is the best representation. |
| octet rule | A guideline stating that atoms tend to gain, lose, or share electrons to achieve a stable electron configuration with eight valence electrons. |
| resonance | The representation of a molecule using two or more equivalent Lewis structures that differ only in the placement of electrons, used to describe bonding when a single structure is inadequate. |
| valence electrons | Electrons in the outermost shell of an atom that participate in bonding and determine many properties of substances. |
| Term | Definition |
|---|---|
| atomic radius | The size of an atom, typically measured as the distance from the nucleus to the outermost electrons. |
| bond angles | The angle formed between two bonds that share a common central atom. |
| bond energy | The average energy required to break a chemical bond between two atoms. |
| bond length | The distance between the nuclei of two bonded atoms, which is affected by bond order and atomic radius. |
| bond order | The number of electron pairs shared between two atoms in a chemical bond, which affects bond energy and bond length. |
| bond polarity | The unequal distribution of electron density in a chemical bond due to differences in electronegativity between atoms. |
| Coulombic repulsion | The electrostatic repulsion between negatively charged electron pairs that determines their spatial arrangement around a central atom. |
| dipole moment | A measure of the separation of positive and negative charge in a polar molecule. |
| electron pair | Two electrons occupying the same orbital, including bonding pairs and lone pairs around a central atom. |
| geometric isomers | Molecules with the same molecular formula but different spatial arrangements of atoms due to restricted rotation around pi bonds. |
| hybrid atomic orbital | An orbital formed by the combination of atomic orbitals on a central atom, used to explain molecular geometry and bonding. |
| hybridization | The mixing of atomic orbitals to form new hybrid orbitals that describe the arrangement of electrons around a central atom. |
| Lewis diagram | A structural representation of a molecule showing the arrangement of valence electrons as dots and bonds between atoms. |
| molecular geometry | The three-dimensional arrangement of atoms around a central atom in a molecule, determined by the positions of bonding and lone pairs. |
| multiple bond | Chemical bonds consisting of more than one electron pair shared between two atoms, such as double or triple bonds. |
| pi bond | A covalent bond formed by sideways overlap of p orbitals, which prevents rotation and is weaker than a sigma bond. |
| polyatomic ion | Charged species composed of two or more atoms bonded together. |
| sigma bond | A covalent bond formed by direct overlap of atomic orbitals along the internuclear axis, allowing rotation around the bond. |
| sp hybridization | The mixing of one s orbital and one p orbital to form two hybrid orbitals with ideal bond angles of 180°. |
| sp2 hybridization | The mixing of one s orbital and two p orbitals to form three hybrid orbitals with ideal bond angles of 120°. |
| sp3 hybridization | The mixing of one s orbital and three p orbitals to form four hybrid orbitals with ideal bond angles of 109.5°. |
| valence orbital | The outermost electron orbitals of an atom that participate in chemical bonding. |
| VSEPR theory | A theory that uses Coulombic repulsion between electron pairs to predict the three-dimensional arrangement of electron pairs and molecular geometry around a central atom. |
| Term | Definition |
|---|---|
| biomolecule | A large organic molecule such as a protein, nucleic acid, carbohydrate, or lipid that is essential to living organisms. |
| contact area | The surface area between molecules that affects the strength of London dispersion forces. |
| dipole moment | A measure of the separation of positive and negative charge in a polar molecule. |
| dipole-dipole interactions | Intermolecular forces between polar molecules resulting from the attraction between their permanent dipoles. |
| dipole-induced dipole interactions | Attractive forces between a polar molecule and a nonpolar molecule, where the polar molecule induces a temporary dipole in the nonpolar molecule. |
| electron cloud | The region surrounding an atom or molecule where electrons are distributed. |
| electronegative atom | An atom with a strong tendency to attract electrons in a covalent bond, such as nitrogen, oxygen, or fluorine. |
| hydrogen bonding | A strong intermolecular force occurring when hydrogen atoms bonded to highly electronegative atoms (N, O, F) are attracted to the negative end of a dipole in another molecule or region. |
| intermolecular forces | Attractive forces between separate molecules or particles that determine many properties of liquids and solids, including boiling point, melting point, and vapor pressure. |
| ion-dipole interactions | Attractive forces between an ion and a polar molecule, where the charged ion interacts with the partial charges on the polar molecule. |
| London dispersion forces | Intermolecular forces resulting from Coulombic interactions between temporary, fluctuating dipoles in molecules. |
| noncovalent interactions | Weak attractive or repulsive forces between molecules or regions of molecules that do not involve the breaking or formation of covalent bonds. |
| nonpolar molecule | A molecule with no net dipole moment due to symmetrical charge distribution. |
| partial charge | A fractional electric charge on an atom within a molecule due to unequal sharing of electrons in a covalent bond. |
| pi bonding | Covalent bonding formed by the sideways overlap of p orbitals, which enhances polarizability. |
| polar molecule | A molecule with an uneven distribution of charge, resulting in a net dipole moment. |
| polarizability | The ability of a molecule's electron cloud to be distorted, creating a temporary dipole in response to an external electric field. |
| temporary dipole | A brief, fluctuating separation of charge in a molecule caused by uneven electron distribution at any given moment. |
| van der Waals forces | A broad category of weak intermolecular forces including London dispersion forces and dipole-dipole interactions. |
| Term | Definition |
|---|---|
| aqueous solvents | Solvents in which water is the dissolving medium, commonly used in chemistry due to water's polar nature. |
| intermolecular interactions | Forces between molecules, such as hydrogen bonding, dipole-dipole forces, and London dispersion forces, that affect the physical and chemical properties of substances. |
| ionic compound | Compounds formed by the electrostatic attraction between positively charged cations and negatively charged anions. |
| miscible | Capable of being mixed in all proportions without separating into distinct phases. |
| molecular compound | Compounds composed of molecules held together by covalent bonds, typically formed between nonmetals. |
| nonaqueous solvents | Solvents that do not use water as the dissolving medium, such as organic solvents or liquid ammonia. |
| solubility | The maximum amount of a solute that can dissolve in a given amount of solvent at a specific temperature, typically expressed in moles per liter (molarity) or grams per 100 mL of solvent. |
| Term | Definition |
|---|---|
| electromagnetic spectrum | The range of all types of electromagnetic radiation, organized by wavelength and frequency, from radio waves to gamma rays. |
| electronic energy levels | Discrete energy states that electrons can occupy in an atom or molecule. |
| electronic transition | The movement of an electron between different energy levels in an atom or molecule, which occurs when a photon is absorbed or emitted. |
| infrared radiation | Electromagnetic radiation with wavelengths between microwave and visible light, associated with molecular vibrational transitions. |
| microwave radiation | Electromagnetic radiation with longer wavelengths and lower frequencies than infrared, associated with molecular rotational transitions. |
| molecular rotational levels | Discrete energy states associated with the rotation of a molecule around its axis. |
| molecular vibrational levels | Discrete energy states associated with the vibration of atoms within a molecule. |
| photon absorption | The process by which matter takes in energy from electromagnetic radiation. |
| photon emission | The process by which matter releases energy in the form of electromagnetic radiation. |
| ultraviolet/visible radiation | Electromagnetic radiation with shorter wavelengths and higher frequencies than infrared, associated with electronic transitions. |
| Term | Definition |
|---|---|
| absorbed photon | A photon taken in by an atom or molecule, increasing the energy of the species by an amount equal to the photon's energy. |
| electromagnetic wave | A wave composed of oscillating electric and magnetic fields that travels at the speed of light and carries energy related to its frequency. |
| electronic transition | The movement of an electron between different energy levels in an atom or molecule, which occurs when a photon is absorbed or emitted. |
| emitted photon | A photon released by an atom or molecule when an electron transitions to a lower energy level, decreasing the energy of the species. |
| frequency | The number of wave cycles that pass a point per unit time, represented by the symbol ν, related to wavelength and the speed of light. |
| photon | A discrete packet of electromagnetic energy with properties related to the frequency and wavelength of light. |
| Planck's constant | The fundamental constant (h) that relates the energy of a photon to its frequency in Planck's equation. |
| Planck's equation | The relationship E = hν that describes how the energy of a photon is proportional to its frequency, where h is Planck's constant. |
| speed of light | The constant velocity at which electromagnetic radiation travels, represented by the symbol c, equal to approximately 3.00 × 10⁸ m/s. |
| wavelength | The distance between successive peaks of an electromagnetic wave, represented by the symbol λ. |
| Term | Definition |
|---|---|
| absorbance | The measure of the amount of light absorbed by a solution, related to concentration and path length when wavelength is held constant. |
| concentration | The amount of solute dissolved in a given volume of solution, typically expressed in molarity or other units of amount per volume. |
| light absorption | The process by which molecules or ions in a solution take in light energy, reducing the intensity of light passing through the solution. |
| maximum absorbance | The wavelength at which a chemical species absorbs the greatest amount of light, also called the optimum wavelength, used to ensure maximum sensitivity in spectrophotometric measurements. |
| molar absorptivity | A constant, denoted as ε, that describes how intensely a specific chemical species absorbs light at a particular wavelength. |
| path length | The distance that light travels through a solution, typically denoted as b in the Beer-Lambert law equation, which is proportional to light absorption. |
| spectrophotometer | An instrument used to measure the absorbance of light by a solution at specific wavelengths. |
| wavelength | The distance between successive peaks of an electromagnetic wave, represented by the symbol λ. |
| Term | Definition |
|---|---|
| boiling point | The temperature at which a liquid vaporizes, directly related to the strength of intermolecular interactions that must be overcome. |
| brittle | The property of a material that causes it to break or shatter easily when subjected to stress, characteristic of ionic solids due to repulsion of like charges. |
| covalent network solids | Solids in which atoms are covalently bonded together in continuous three-dimensional or two-dimensional networks, such as diamond and graphite. |
| ductile | The property of a material that allows it to be drawn or stretched into thin wires without breaking. |
| intermolecular forces | Attractive forces between separate molecules or particles that determine many properties of liquids and solids, including boiling point, melting point, and vapor pressure. |
| interstitial alloy | An alloy in which smaller atoms occupy the spaces between larger atoms in the crystal lattice, making the structure more rigid and decreasing malleability and ductility. |
| ionic solids | Solids composed of cations and anions held together by strong electrostatic forces, characterized by low vapor pressures, high melting and boiling points, and brittleness. |
| macroscopic properties | Observable physical and chemical characteristics of a substance that can be measured at the bulk level, such as melting point, boiling point, and vapor pressure. |
| malleable | The property of a material that allows it to be hammered or pressed into thin sheets without breaking. |
| melting point | The temperature at which a solid transitions to a liquid, which tends to correlate with the strength of intermolecular interactions. |
| metallic solids | Solids composed of metal atoms with delocalized valence electrons that move freely, resulting in good electrical and thermal conductivity, malleability, and ductility. |
| molecular solids | Solids composed of distinct molecules held together by relatively weak intermolecular forces, generally having low melting points. |
| molten state | The liquid state of an ionic solid in which ions are mobile and able to conduct electricity. |
| noncovalent interactions | Weak attractive or repulsive forces between molecules or regions of molecules that do not involve the breaking or formation of covalent bonds. |
| particulate-level structure | The arrangement and organization of atoms, ions, or molecules that make up a substance at the atomic and molecular scale. |
| polymers | Large molecules composed of repeating units of smaller molecules linked together, whose properties depend on noncovalent interactions and molecular shape. |
| valence electrons | Electrons in the outermost shell of an atom that participate in bonding and determine many properties of substances. |
| vapor pressure | The pressure exerted by a vapor in equilibrium with its liquid or solid phase at a given temperature. |
| Term | Definition |
|---|---|
| amorphous solid | A solid in which particles do not have a regular or orderly arrangement. |
| collision frequency | The number of collisions between reactant particles per unit time. |
| crystalline solid | A solid in which particles are arranged in a regular, repeating three-dimensional structure. |
| gas | A phase of matter in which particles are in constant motion with minimal intermolecular forces, resulting in no definite volume or shape. |
| hydrogen bonding | A strong intermolecular force occurring when hydrogen atoms bonded to highly electronegative atoms (N, O, F) are attracted to the negative end of a dipole in another molecule or region. |
| interparticle interactions | Forces between particles in a system that affect the energy changes during physical and chemical processes. |
| liquid | A phase of matter in which particles are in close contact and in continual motion and collision with one another. |
| molar volume | The volume occupied by one mole of a substance; typically similar between solid and liquid phases because particles are in close contact. |
| particulate model | A representation of matter showing individual atoms, molecules, or ions and their interactions to describe chemical processes at the molecular level. |
| polarity | The distribution of electric charge in a molecule, determining its ability to interact with polar and nonpolar substances. |
| Term | Definition |
|---|---|
| Dalton's Law of Partial Pressures | The principle that the total pressure of a gas mixture equals the sum of the partial pressures of the individual gas components. |
| ideal gas law | The equation PV = nRT that relates pressure, volume, number of moles, and temperature of an ideal gas. |
| macroscopic properties | Observable physical and chemical characteristics of a substance that can be measured at the bulk level, such as melting point, boiling point, and vapor pressure. |
| mole fraction | The ratio of the number of moles of one component to the total number of moles in a mixture, used to relate partial pressure to total pressure. |
| partial pressure | The pressure exerted by a single gas in a mixture of gases, used in equilibrium expressions for gas-phase reactions. |
| Term | Definition |
|---|---|
| average kinetic energy | The mean kinetic energy of particles in a sample, related to the average velocity by the equation KE = 1/2 mv². |
| Kelvin temperature | Absolute temperature measured on the Kelvin scale, which is directly proportional to the average kinetic energy of particles in a sample. |
| kinetic molecular theory (KMT) | A theory that relates the macroscopic properties of gases to the motion and kinetic energy of particles at the molecular level. |
| macroscopic properties | Observable physical and chemical characteristics of a substance that can be measured at the bulk level, such as melting point, boiling point, and vapor pressure. |
| Maxwell-Boltzmann distribution | A curve that describes how particle energies are distributed in a sample at a given temperature, used to estimate the fraction of collisions with sufficient energy to produce a reaction. |
| particulate model | A representation of matter showing individual atoms, molecules, or ions and their interactions to describe chemical processes at the molecular level. |
| random motion | The continuous, unpredictable movement of particles in all directions with varying speeds. |
| Term | Definition |
|---|---|
| condensation | The process by which a gas converts to a liquid. |
| interparticle attractions | Attractive forces between gas molecules that reduce pressure and cause real gases to deviate from ideal behavior. |
| interparticle forces | Attractive or repulsive forces between gas molecules that cause deviations from ideal gas behavior, particularly at conditions near condensation. |
| non-ideal behaviors | Deviations from the predictions of the ideal gas law that occur when real gases do not follow the assumptions of the ideal gas model. |
| particle volumes | The actual volume occupied by gas molecules themselves, which becomes significant at extremely high pressures and causes deviations from ideal gas law predictions. |
| Term | Definition |
|---|---|
| heterogeneous mixture | A mixture in which macroscopic properties vary depending on the location within the mixture. |
| homogeneous mixture | A mixture with uniform composition and properties throughout the sample. |
| macroscopic properties | Observable physical and chemical characteristics of a substance that can be measured at the bulk level, such as melting point, boiling point, and vapor pressure. |
| molarity | A measure of solution concentration expressed as the number of moles of solute dissolved per liter of solution. |
| solute | The substance being dissolved in a solution, typically present in a smaller amount than the solvent. |
| solution | A homogeneous mixture in which one or more solutes are uniformly dissolved in a solvent. |
| solvent | The substance, typically a liquid, in which a solute dissolves to form a solution. |
| Term | Definition |
|---|---|
| concentration | The amount of solute dissolved in a given volume of solution, typically expressed in molarity or other units of amount per volume. |
| interaction | The forces or bonds between components in a mixture, such as hydrogen bonding, ionic interactions, or dispersion forces. |
| mixture | Materials that contain atoms, molecules, or formula units of two or more types, whose relative proportions can vary. |
| particulate model | A representation of matter showing individual atoms, molecules, or ions and their interactions to describe chemical processes at the molecular level. |
| solution | A homogeneous mixture in which one or more solutes are uniformly dissolved in a solvent. |
| Term | Definition |
|---|---|
| chromatogram | The visual result of a chromatography separation showing the separated components as distinct spots or bands. |
| chromatography | A separation technique that separates chemical species based on differences in their intermolecular interactions with a mobile phase and a stationary phase. |
| column chromatography | A chromatographic separation technique using a column filled with a stationary phase material through which a mobile phase flows. |
| distillation | A separation technique that separates chemical species based on differences in their vapor pressures and boiling points. |
| filtration | A separation technique that uses a physical barrier to separate solid particles from a liquid or gas based on particle size. |
| intermolecular interactions | Forces between molecules, such as hydrogen bonding, dipole-dipole forces, and London dispersion forces, that affect the physical and chemical properties of substances. |
| liquid solution | A homogeneous mixture where a solute is dissolved in a liquid solvent, forming a single phase. |
| mobile phase | In chromatography, the solvent or gas that moves through the stationary phase and carries the components of a mixture. |
| paper chromatography | A chromatographic separation technique using paper as the stationary phase and a liquid solvent as the mobile phase. |
| polarity | The distribution of electric charge in a molecule, determining its ability to interact with polar and nonpolar substances. |
| stationary phase | In chromatography, the solid or liquid material that remains fixed and interacts with the components of a mixture to separate them. |
| thin-layer chromatography | A chromatographic separation technique using a thin layer of absorbent material on a solid support as the stationary phase. |
| vapor pressure | The pressure exerted by a vapor in equilibrium with its liquid or solid phase at a given temperature. |
| Term | Definition |
|---|---|
| chemical change | A process in which substances are rearranged into new combinations, resulting in the formation of new substances with different properties. |
| mixture | Materials that contain atoms, molecules, or formula units of two or more types, whose relative proportions can vary. |
| phase | A distinct state of matter: solid, liquid, or gas. |
| physical change | A change in matter that does not alter the chemical composition or identity of the substance. |
| precipitate | A solid substance that forms and separates from a solution during a chemical reaction. |
| Term | Definition |
|---|---|
| balanced chemical equation | A chemical equation where the number of atoms of each element is equal on both the reactant and product sides. |
| chemical change | A process in which substances are rearranged into new combinations, resulting in the formation of new substances with different properties. |
| complete ionic equation | A balanced equation that shows all ions and molecules present in solution, including spectator ions. |
| conservation of charge | The principle that the total electric charge is neither created nor destroyed in a chemical reaction; total charge is equal on both sides of the equation. |
| conservation of mass | The principle that mass is neither created nor destroyed in a chemical reaction; the total mass of reactants equals the total mass of products. |
| molecular equation | A balanced chemical equation that represents all reactants and products in their molecular form. |
| net ionic equation | A symbolic representation of a chemical reaction that shows only the ions and molecules that actually participate in the reaction, excluding spectator ions. |
| physical change | A change in matter that does not alter the chemical composition or identity of the substance. |
| Term | Definition |
|---|---|
| balanced chemical equation | A chemical equation where the number of atoms of each element is equal on both the reactant and product sides. |
| chemical reaction | A process in which substances are transformed into different substances through the breaking and forming of chemical bonds. |
| particulate model | A representation of matter showing individual atoms, molecules, or ions and their interactions to describe chemical processes at the molecular level. |
| physical process | A change in the state or properties of matter that does not alter the identity of the substances involved. |
| symbolic representation | A depiction of chemical reactions using chemical formulas, symbols, and equations to represent reactants and products. |
| Term | Definition |
|---|---|
| bond interactions | The forces between atoms or molecules, including chemical bonds and intermolecular forces, that determine the properties and behavior of substances. |
| chemical process | A transformation in which substances are converted into different substances through the breaking and forming of chemical bonds. |
| dissolution | The process by which a solute dissolves in a solvent to form a solution, involving the breaking of bonds or interactions in the solute and formation of new interactions with the solvent. |
| intermolecular interactions | Forces between molecules, such as hydrogen bonding, dipole-dipole forces, and London dispersion forces, that affect the physical and chemical properties of substances. |
| ion-dipole interactions | Attractive forces between an ion and a polar molecule, where the charged ion interacts with the partial charges on the polar molecule. |
| ionic bonds | Chemical bonds formed between positively and negatively charged ions through electrostatic attraction. |
| macroscopic characteristics | Observable properties of matter that can be seen and measured without a microscope, such as color, state, temperature, and solubility. |
| phase transition | The process by which a substance changes from one state of matter to another (solid, liquid, or gas). |
| physical process | A change in the state or properties of matter that does not alter the identity of the substances involved. |
| Term | Definition |
|---|---|
| atom conservation | The principle that atoms cannot be created, destroyed, or changed during a chemical process, so the total number and type of atoms remain constant. |
| balanced chemical equation | A chemical equation where the number of atoms of each element is equal on both the reactant and product sides. |
| coefficients | The numbers placed in front of chemical formulas in a balanced equation that indicate the relative proportions of reactants and products involved in the reaction. |
| ideal gas law | The equation PV = nRT that relates pressure, volume, number of moles, and temperature of an ideal gas. |
| molarity | A measure of solution concentration expressed as the number of moles of solute dissolved per liter of solution. |
| mole concept | A fundamental chemistry concept that relates the number of particles (atoms, molecules, or ions) to measurable quantities through Avogadro's number. |
| product | Substances formed as a result of a chemical reaction. |
| reactant | Substances that are consumed in a chemical reaction to form products. |
| stoichiometric calculations | Quantitative calculations using balanced chemical equations and mole ratios to determine amounts of reactants consumed or products formed in a chemical reaction. |
| Term | Definition |
|---|---|
| analyte | The substance in a solution whose amount or concentration is being determined during a titration. |
| endpoint | The observable event or change in property (such as color) that indicates when the equivalence point has been reached in a titration. |
| equivalence point | The point in a titration where the analyte is completely consumed by the titrant in a quantitative reaction. |
| titrant | A solution of known concentration that is added to an analyte during a titration to determine the amount of analyte present. |
| titration | An analytical procedure used to determine the amount of an analyte in solution by reacting it with a titrant of known concentration. |
| Term | Definition |
|---|---|
| acid-base reaction | A chemical reaction involving the transfer of one or more protons (H⁺ ions) between chemical species. |
| aqueous solution | A solution in which water is the solvent. |
| combustion | A type of oxidation-reduction reaction in which a species reacts with oxygen gas to produce products such as carbon dioxide and water. |
| electron transfer | The movement of one or more electrons from one chemical species to another in a redox reaction. |
| hydrocarbons | Organic compounds composed of carbon and hydrogen atoms that undergo complete combustion to produce carbon dioxide and water. |
| insoluble | Unable to dissolve in a solvent, such as water; describes compounds that form as precipitates. |
| ionic compound | Compounds formed by the electrostatic attraction between positively charged cations and negatively charged anions. |
| oxidation numbers | Numbers assigned to atoms in reactants and products to track electron transfer and identify oxidized and reduced species in a redox reaction. |
| oxidation-reduction reaction | A chemical reaction involving the transfer of one or more electrons between chemical species, indicated by changes in oxidation numbers. |
| oxidized | The process in which a species loses electrons in a redox reaction. |
| precipitation reaction | A chemical reaction in which ions in aqueous solution combine to produce an insoluble or sparingly soluble ionic compound. |
| proton transfer | The movement of a proton (H⁺) from one species to another in an acid-base reaction. |
| reduced | The process in which a species gains electrons in a redox reaction. |
| sparingly soluble | Slightly soluble in a solvent; describes ionic compounds that form precipitates when ions combine in aqueous solution. |
| Term | Definition |
|---|---|
| aqueous solution | A solution in which water is the solvent. |
| Brønsted-Lowry acid | A species that donates a proton (H⁺) in a chemical reaction. |
| Brønsted-Lowry base | A species that accepts a proton (H⁺) in a chemical reaction. |
| conjugate acid-base pair | Two species that differ by one proton, where one is the acid form and the other is the base form of the same substance. |
| ionization | The process by which an acid or base separates into ions when dissolved in water. |
| proton transfer | The movement of a proton (H⁺) from one species to another in an acid-base reaction. |
| Term | Definition |
|---|---|
| balanced redox reaction equation | A chemical equation for an oxidation-reduction reaction where the number of electrons lost equals the number of electrons gained, and all atoms and charges are balanced. |
| half-reaction | Separate equations showing either the oxidation process (loss of electrons) or the reduction process (gain of electrons) in a redox reaction. |
| Term | Definition |
|---|---|
| activation energy | The minimum energy required for reactants to overcome the energy barrier and proceed to products in a chemical reaction. |
| elementary reaction | A single-step reaction that represents one molecular event in a reaction mechanism, with a specific rate law determined by its molecularity. |
| energetics | The energy-related properties and changes associated with chemical reactions and processes. |
| multistep reaction | A chemical reaction that proceeds through two or more elementary steps rather than occurring in a single step. |
| overall energy change | The difference in total energy between reactants and products in a chemical reaction; also known as the enthalpy change (ΔH). |
| reaction energy profile | A diagram that plots energy versus reaction progress, showing the activation energy and energy changes for each step in a multistep reaction. |
| reaction mechanism | The sequence of elementary steps that describes how a reaction proceeds at the molecular level. |
| Term | Definition |
|---|---|
| catalyst | A substance that increases the rate of a chemical reaction without being consumed in the reaction. |
| kinetics | The study of the rate at which a chemical reaction occurs and the factors that influence this rate. |
| product concentrations | The amount of products formed in a given volume as a reaction progresses. |
| reactant concentration | The amount of a reactant present in a given volume of solution, typically expressed in molarity (mol/L). |
| reaction rate | The speed at which reactants are converted to products per unit of time in a chemical reaction. |
| stoichiometry | The quantitative relationship between reactants and products in a balanced chemical equation that determines the rates of change of their concentrations. |
| surface area | A factor that influences reaction rate by affecting the contact between reactants, particularly in heterogeneous reactions. |
| temperature | A factor that influences reaction rate by affecting the kinetic energy and collision frequency of reactant molecules. |
| Term | Definition |
|---|---|
| acid-base catalysis | A catalytic mechanism in which a catalyst facilitates a reaction by transferring a proton to or from a reactant or intermediate. |
| activation energy | The minimum energy required for reactants to overcome the energy barrier and proceed to products in a chemical reaction. |
| catalyst | A substance that increases the rate of a chemical reaction without being consumed in the reaction. |
| covalent bonding | A chemical bond formed by the sharing of electrons between atoms. |
| effective collisions | Collisions between reactant molecules that occur with sufficient energy and proper orientation to result in a reaction. |
| elementary reaction | A single-step reaction that represents one molecular event in a reaction mechanism, with a specific rate law determined by its molecularity. |
| enzyme | A biological catalyst that speeds up chemical reactions by binding to reactants and lowering the activation energy. |
| rate-determining step | The slowest elementary step in a reaction mechanism that controls the overall rate of the reaction. |
| reaction coordinate | A diagram or pathway showing the energy changes that occur as reactants are converted to products during a reaction. |
| reaction intermediate | A species that is produced in one elementary step of a reaction mechanism and consumed in a subsequent step, not appearing in the overall reaction. |
| reaction mechanism | The sequence of elementary steps that describes how a reaction proceeds at the molecular level. |
| surface catalysis | A catalytic process in which reactants or intermediates bind to or form covalent bonds with a solid surface, creating new reaction pathways. |
| Term | Definition |
|---|---|
| initial rates method | An experimental technique for determining reaction order by comparing the initial rates of a reaction under different initial concentrations of reactants. |
| overall order | The sum of all the individual reaction orders (powers) for each reactant in the rate law expression. |
| rate constant | The proportionality constant in a rate law expression that relates reaction rate to reactant concentrations; its value depends on temperature. |
| rate law | A mathematical expression that relates the reaction rate to the concentrations of reactants, with each concentration raised to a power (order). |
| reactant concentration | The amount of a reactant present in a given volume of solution, typically expressed in molarity (mol/L). |
| reaction order | The power to which the concentration of a reactant is raised in the rate law expression; indicates how the reaction rate depends on that reactant's concentration. |
| reaction rate | The speed at which reactants are converted to products per unit of time in a chemical reaction. |
| Term | Definition |
|---|---|
| first order reaction | A reaction whose rate depends on the concentration of one reactant raised to the first power; characterized by a linear plot of ln[A] versus time. |
| half-life | The time required for the concentration of a reactant to decrease to half its initial value; for first order reactions, the half-life is constant and independent of initial concentration. |
| radioactive decay | The spontaneous process by which unstable atomic nuclei emit radiation and transform into more stable forms; follows first order kinetics. |
| rate constant | The proportionality constant in a rate law expression that relates reaction rate to reactant concentrations; its value depends on temperature. |
| rate law | A mathematical expression that relates the reaction rate to the concentrations of reactants, with each concentration raised to a power (order). |
| reaction order | The power to which the concentration of a reactant is raised in the rate law expression; indicates how the reaction rate depends on that reactant's concentration. |
| second order reaction | A reaction whose rate depends on the concentration of one reactant raised to the second power, or on the concentrations of two reactants each raised to the first power; characterized by a linear plot of 1/[A] versus time. |
| zeroth order reaction | A reaction whose rate is independent of the concentration of reactants; characterized by a linear plot of [A] versus time. |
| Term | Definition |
|---|---|
| collision | The event in which reactant particles come together with sufficient energy and proper orientation to form products. |
| elementary reaction | A single-step reaction that represents one molecular event in a reaction mechanism, with a specific rate law determined by its molecularity. |
| rate law | A mathematical expression that relates the reaction rate to the concentrations of reactants, with each concentration raised to a power (order). |
| stoichiometry | The quantitative relationship between reactants and products in a balanced chemical equation that determines the rates of change of their concentrations. |
| Term | Definition |
|---|---|
| activation energy | The minimum energy required for reactants to overcome the energy barrier and proceed to products in a chemical reaction. |
| bond-breaking | The process of breaking chemical bonds in reactant molecules during a collision. |
| bond-making | The process of forming new chemical bonds to create product molecules during a collision. |
| collision frequency | The number of collisions between reactant particles per unit time. |
| collision orientation | The spatial arrangement and relative positioning of reactant molecules during a collision, which determines whether bonds can rearrange in the required manner. |
| elementary reaction | A single-step reaction that represents one molecular event in a reaction mechanism, with a specific rate law determined by its molecularity. |
| Maxwell-Boltzmann distribution | A curve that describes how particle energies are distributed in a sample at a given temperature, used to estimate the fraction of collisions with sufficient energy to produce a reaction. |
| particle energy distribution | The range and frequency of different energy levels among particles in a system at a given temperature. |
| successful collision | A collision between reactant particles that has both sufficient energy to overcome activation energy and proper orientation to allow bond rearrangement. |
| Term | Definition |
|---|---|
| activation energy | The minimum energy required for reactants to overcome the energy barrier and proceed to products in a chemical reaction. |
| Arrhenius equation | A mathematical relationship that describes how the rate of an elementary reaction depends on temperature and activation energy. |
| bond-breaking | The process of breaking chemical bonds in reactant molecules during a collision. |
| bond-making | The process of forming new chemical bonds to create product molecules during a collision. |
| elementary reaction | A single-step reaction that represents one molecular event in a reaction mechanism, with a specific rate law determined by its molecularity. |
| overall energy change | The difference in total energy between reactants and products in a chemical reaction; also known as the enthalpy change (ΔH). |
| reaction coordinate | A diagram or pathway showing the energy changes that occur as reactants are converted to products during a reaction. |
| reaction energy profile | A diagram that plots energy versus reaction progress, showing the activation energy and energy changes for each step in a multistep reaction. |
| transition state | The highest energy point on a reaction energy profile, representing the arrangement of atoms at the peak of the activation energy barrier. |
| Term | Definition |
|---|---|
| balanced chemical equation | A chemical equation where the number of atoms of each element is equal on both the reactant and product sides. |
| catalyst | A substance that increases the rate of a chemical reaction without being consumed in the reaction. |
| elementary reaction | A single-step reaction that represents one molecular event in a reaction mechanism, with a specific rate law determined by its molecularity. |
| product | Substances formed as a result of a chemical reaction. |
| reactant | Substances that are consumed in a chemical reaction to form products. |
| reaction intermediate | A species that is produced in one elementary step of a reaction mechanism and consumed in a subsequent step, not appearing in the overall reaction. |
| reaction mechanism | The sequence of elementary steps that describes how a reaction proceeds at the molecular level. |
| Term | Definition |
|---|---|
| elementary reaction | A single-step reaction that represents one molecular event in a reaction mechanism, with a specific rate law determined by its molecularity. |
| irreversible | A reaction step that proceeds in only one direction and does not reverse under the reaction conditions. |
| molecularity | The number of molecules that participate in an elementary step. |
| rate law | A mathematical expression that relates the reaction rate to the concentrations of reactants, with each concentration raised to a power (order). |
| rate-determining step | The slowest elementary step in a reaction mechanism that controls the overall rate of the reaction. |
| reaction mechanism | The sequence of elementary steps that describes how a reaction proceeds at the molecular level. |
| Term | Definition |
|---|---|
| elementary reaction | A single-step reaction that represents one molecular event in a reaction mechanism, with a specific rate law determined by its molecularity. |
| pre-equilibrium approximation | A method used to derive a rate law when a fast elementary step precedes a slow step, assuming the fast step reaches equilibrium quickly. |
| rate law | A mathematical expression that relates the reaction rate to the concentrations of reactants, with each concentration raised to a power (order). |
| rate-determining step | The slowest elementary step in a reaction mechanism that controls the overall rate of the reaction. |
| reaction mechanism | The sequence of elementary steps that describes how a reaction proceeds at the molecular level. |
| Term | Definition |
|---|---|
| chemical transformation | A process in which substances are converted into different substances through the breaking and forming of chemical bonds. |
| dissolution process | The process by which a solute dissolves in a solvent to form a solution, which can involve energy changes. |
| endothermic reaction | A chemical reaction that absorbs thermal energy from the surroundings, resulting in a positive enthalpy change. |
| exothermic reaction | A chemical reaction that releases thermal energy to the surroundings, resulting in a negative enthalpy change. |
| heat transfer | The process by which thermal energy is transferred between particles in thermal contact through collisions. |
| intermolecular interactions | Forces between molecules, such as hydrogen bonding, dipole-dipole forces, and London dispersion forces, that affect the physical and chemical properties of substances. |
| interparticle interactions | Forces between particles in a system that affect the energy changes during physical and chemical processes. |
| phase transition | The process by which a substance changes from one state of matter to another (solid, liquid, or gas). |
| physical transformation | A process in which the physical state or form of a substance changes without altering its chemical composition. |
| surroundings | Everything outside the system with which the system can exchange energy and matter. |
| system | The part of the universe being studied, which can exchange energy and matter with its surroundings. |
| temperature changes | Variations in the thermal energy of a substance that indicate energy changes in a system. |
| Term | Definition |
|---|---|
| chemical transformation | A process in which substances are converted into different substances through the breaking and forming of chemical bonds. |
| endothermic reaction | A chemical reaction that absorbs thermal energy from the surroundings, resulting in a positive enthalpy change. |
| energy diagram | A visual representation showing the energy changes that occur during a chemical or physical process, including initial and final energy states. |
| exothermic reaction | A chemical reaction that releases thermal energy to the surroundings, resulting in a negative enthalpy change. |
| physical transformation | A process in which the physical state or form of a substance changes without altering its chemical composition. |
| Term | Definition |
|---|---|
| heat transfer | The process by which thermal energy is transferred between particles in thermal contact through collisions. |
| kinetic energy | The energy possessed by particles due to their motion; greater in warmer bodies and lower in cooler bodies. |
| molecular collisions | Interactions between particles that can result in the transfer of energy between them. |
| temperature | A factor that influences reaction rate by affecting the kinetic energy and collision frequency of reactant molecules. |
| thermal energy | The total kinetic energy of particles in a substance due to their random motion. |
| thermal equilibrium | The state reached when two bodies in thermal contact have the same average kinetic energy and temperature, with no net transfer of thermal energy. |
| Term | Definition |
|---|---|
| calorimetry | An experimental technique used to measure the amount of heat transferred between systems. |
| dissolution | The process by which a solute dissolves in a solvent to form a solution, involving the breaking of bonds or interactions in the solute and formation of new interactions with the solvent. |
| endothermic reaction | A chemical reaction that absorbs thermal energy from the surroundings, resulting in a positive enthalpy change. |
| exothermic reaction | A chemical reaction that releases thermal energy to the surroundings, resulting in a negative enthalpy change. |
| first law of thermodynamics | The principle that energy is conserved in chemical and physical processes; energy cannot be created or destroyed, only transferred or transformed. |
| heat | Energy transferred between two systems due to a difference in temperature. |
| heat transfer equation | The mathematical relationship q = mcΔT used to calculate heat absorbed or released, where m is mass, c is specific heat capacity, and ΔT is the change in temperature. |
| molar heat capacity | The amount of thermal energy required to raise the temperature of one mole of a substance by one degree Celsius. |
| phase transition | The process by which a substance changes from one state of matter to another (solid, liquid, or gas). |
| specific heat capacity | The amount of thermal energy required to raise the temperature of one gram of a substance by one degree Celsius. |
| thermal energy | The total kinetic energy of particles in a substance due to their random motion. |
| Term | Definition |
|---|---|
| condensation | The process by which a gas converts to a liquid. |
| freezing | The phase transition process in which a liquid changes to a solid, releasing energy. |
| heat absorbed | The amount of thermal energy taken in by a system, typically during endothermic processes like melting or boiling. |
| heat released | The amount of thermal energy given off by a system, typically during exothermic processes like freezing or condensation. |
| melting | The phase transition process in which a solid changes to a liquid, requiring energy absorption. |
| molar enthalpy | The amount of heat energy absorbed or released per mole of substance during a process, typically measured in kJ/mol. |
| molar enthalpy of condensation | The amount of heat energy released when one mole of gas condenses to a liquid, equal to the negative of the molar enthalpy of vaporization. |
| molar enthalpy of fusion | The amount of heat energy required to melt one mole of a solid substance at its melting point, or released when one mole of liquid freezes. |
| molar enthalpy of vaporization | The amount of heat energy required to vaporize one mole of a liquid substance at its boiling point, or released when one mole of gas condenses. |
| phase transition | The process by which a substance changes from one state of matter to another (solid, liquid, or gas). |
| vaporization | The phase transition process in which a liquid changes to a gas, requiring energy absorption. |
| Term | Definition |
|---|---|
| bond breaking and forming | The process of breaking existing chemical bonds in reactants and forming new chemical bonds in products, which results in energy changes during a reaction. |
| chemical potential energy | The energy stored in the bonds of a substance that can be released or absorbed during a chemical reaction. |
| endothermic reaction | A chemical reaction that absorbs thermal energy from the surroundings, resulting in a positive enthalpy change. |
| enthalpy change | The difference in enthalpy between products and reactants in a chemical or physical process, representing the heat absorbed or released. |
| exothermic reaction | A chemical reaction that releases thermal energy to the surroundings, resulting in a negative enthalpy change. |
| heat (q) | The thermal energy transferred between a system and its surroundings, measured in joules or kilojoules. |
| kinetic energy of particles | The energy of motion of particles in a substance, which changes as chemical potential energy is released or absorbed, manifesting as a temperature change. |
| molar enthalpy of reaction | The enthalpy change per mole of a reactant or product in a chemical reaction, indicating the heat absorbed or released per mole at constant pressure. |
| thermal equilibrium | The state reached when two bodies in thermal contact have the same average kinetic energy and temperature, with no net transfer of thermal energy. |
| Term | Definition |
|---|---|
| bond energy | The average energy required to break a chemical bond between two atoms. |
| bonds broken | The breaking of chemical bonds in reactant molecules, which requires energy input to the system. |
| bonds formed | The formation of new chemical bonds in product molecules, which releases energy from the system. |
| endothermic reaction | A chemical reaction that absorbs thermal energy from the surroundings, resulting in a positive enthalpy change. |
| enthalpy change | The difference in enthalpy between products and reactants in a chemical or physical process, representing the heat absorbed or released. |
| exothermic reaction | A chemical reaction that releases thermal energy to the surroundings, resulting in a negative enthalpy change. |
| potential energy | The stored energy in chemical bonds and molecular structures that can be released or absorbed during a reaction. |
| Term | Definition |
|---|---|
| chemical process | A transformation in which substances are converted into different substances through the breaking and forming of chemical bonds. |
| enthalpy change | The difference in enthalpy between products and reactants in a chemical or physical process, representing the heat absorbed or released. |
| physical process | A change in the state or properties of matter that does not alter the identity of the substances involved. |
| product | Substances formed as a result of a chemical reaction. |
| reactant | Substances that are consumed in a chemical reaction to form products. |
| standard enthalpies of formation | The enthalpy change when one mole of a compound is formed from its elements in their standard states. |
| Term | Definition |
|---|---|
| chemical process | A transformation in which substances are converted into different substances through the breaking and forming of chemical bonds. |
| energy change | The difference in energy between the initial and final states of a system during a process or reaction step. |
| enthalpy | The total heat content of a system; at constant pressure, the enthalpy change equals the thermal energy transferred to or from the surroundings during a chemical or physical process. |
| enthalpy change | The difference in enthalpy between products and reactants in a chemical or physical process, representing the heat absorbed or released. |
| first law of thermodynamics | The principle that energy is conserved in chemical and physical processes; energy cannot be created or destroyed, only transferred or transformed. |
| Hess's law | The principle that the enthalpy change of an overall reaction equals the sum of the enthalpy changes of the individual steps in the reaction sequence. |
| physical process | A change in the state or properties of matter that does not alter the identity of the substances involved. |
| potential energy | The stored energy in chemical bonds and molecular structures that can be released or absorbed during a reaction. |
| thermal energy transfer | The movement of heat energy to or from the surroundings during a chemical or physical process. |
| Term | Definition |
|---|---|
| concentration | The amount of solute dissolved in a given volume of solution, typically expressed in molarity or other units of amount per volume. |
| disturbance | A change or stress applied to a system at equilibrium that causes Q to differ from K and shifts the system out of equilibrium. |
| equilibrium | The state in which the forward and reverse reaction rates are equal, resulting in constant concentrations or partial pressures of reactants and products. |
| equilibrium constant | A numerical value that expresses the ratio of products to reactants at equilibrium, indicating the extent to which a reaction proceeds. |
| partial pressure | The pressure exerted by a single gas in a mixture of gases, used in equilibrium expressions for gas-phase reactions. |
| reaction quotient | A value calculated using the same expression as the equilibrium constant but using current (non-equilibrium) concentrations or partial pressures. |
| Term | Definition |
|---|---|
| absorption | The process by which a gas is taken up by a solid or liquid. |
| concentration | The amount of solute dissolved in a given volume of solution, typically expressed in molarity or other units of amount per volume. |
| condensation | The process by which a gas converts to a liquid. |
| desorption | The process by which an absorbed gas is released from a solid or liquid. |
| dissolution | The process by which a solute dissolves in a solvent to form a solution, involving the breaking of bonds or interactions in the solute and formation of new interactions with the solvent. |
| dynamic equilibrium | A state of equilibrium in which forward and reverse reactions continue to occur at equal rates, maintaining constant macroscopic properties. |
| electron transfer | The movement of one or more electrons from one chemical species to another in a redox reaction. |
| equilibrium | The state in which the forward and reverse reaction rates are equal, resulting in constant concentrations or partial pressures of reactants and products. |
| evaporation | The process by which a liquid converts to a gas. |
| partial pressure | The pressure exerted by a single gas in a mixture of gases, used in equilibrium expressions for gas-phase reactions. |
| precipitation | The process by which a dissolved solute forms a solid and separates from a solution. |
| proton transfer | The movement of a proton (H⁺) from one species to another in an acid-base reaction. |
| reversible process | A chemical or physical process that can occur in both forward and reverse directions, such as evaporation-condensation or dissolution-precipitation. |
| Term | Definition |
|---|---|
| balanced chemical equation | A chemical equation where the number of atoms of each element is equal on both the reactant and product sides. |
| dissolution | The process by which a solute dissolves in a solvent to form a solution, involving the breaking of bonds or interactions in the solute and formation of new interactions with the solvent. |
| equilibrium system | A system in which the forward and reverse reactions occur at equal rates, resulting in constant concentrations of reactants and products. |
| Ksp | The solubility product constant; the equilibrium constant for the dissolution of a sparingly soluble salt into its ions. |
| molar solubility | The solubility of a substance expressed as the number of moles of solute that dissolve per liter of solution in a saturated solution. |
| salt | An ionic compound formed from the reaction of an acid and a base. |
| saturated solution | A solution that contains the maximum amount of dissolved solute at a given temperature, in equilibrium with undissolved solute. |
| solubility | The maximum amount of a solute that can dissolve in a given amount of solvent at a specific temperature, typically expressed in moles per liter (molarity) or grams per 100 mL of solvent. |
| solubility rules | Guidelines that predict whether an ionic compound is soluble or insoluble in water based on the identity of the cation and anion. |
| soluble salts | Ionic compounds that dissolve readily in water, typically corresponding to Ksp values greater than 1. |
| stoichiometry | The quantitative relationship between reactants and products in a balanced chemical equation that determines the rates of change of their concentrations. |
| Term | Definition |
|---|---|
| common ion | An ion that is already present in a solution and is also produced by the dissolution of a salt added to that solution. |
| common-ion effect | The phenomenon in which the solubility of a salt is reduced when dissolved in a solution that already contains one of the ions present in the salt. |
| dissolution | The process by which a solute dissolves in a solvent to form a solution, involving the breaking of bonds or interactions in the solute and formation of new interactions with the solvent. |
| Ksp | The solubility product constant; the equilibrium constant for the dissolution of a sparingly soluble salt into its ions. |
| Le Châtelier's principle | A principle stating that when a system at equilibrium is disturbed, the system shifts to counteract the disturbance and re-establish equilibrium. |
| salt | An ionic compound formed from the reaction of an acid and a base. |
| solubility | The maximum amount of a solute that can dissolve in a given amount of solvent at a specific temperature, typically expressed in moles per liter (molarity) or grams per 100 mL of solvent. |
| Term | Definition |
|---|---|
| equilibrium state | The condition reached when the rate of the forward reaction equals the rate of the reverse reaction, resulting in no net change in the amounts of reactants and products. |
| forward reaction | The reaction pathway in which reactants are converted to products. |
| net conversion | The overall change in the amounts of reactants or products as a result of the forward and reverse reactions occurring simultaneously. |
| reaction rate | The speed at which reactants are converted to products per unit of time in a chemical reaction. |
| reverse reaction | The reaction that proceeds from products back to reactants, opposite to the direction written in the balanced chemical equation. |
| reversible reaction | A chemical reaction that can proceed in both the forward and reverse directions, with reactants forming products and products reforming reactants. |
| Term | Definition |
|---|---|
| equilibrium constant | A numerical value that expresses the ratio of products to reactants at equilibrium, indicating the extent to which a reaction proceeds. |
| equilibrium expression | A mathematical equation that relates the concentrations or partial pressures of reactants and products at equilibrium, expressed as Kc or Kp. |
| Kc | The equilibrium constant expressed in terms of molar concentrations of reactants and products at equilibrium. |
| Kp | The equilibrium constant expressed in terms of partial pressures of gaseous reactants and products at equilibrium. |
| law of mass action | The principle that the equilibrium expression for a reversible reaction is the ratio of the concentrations (or partial pressures) of products to reactants, each raised to the power of their stoichiometric coefficients. |
| partial pressure | The pressure exerted by a single gas in a mixture of gases, used in equilibrium expressions for gas-phase reactions. |
| reaction quotient | A value calculated using the same expression as the equilibrium constant but using current (non-equilibrium) concentrations or partial pressures. |
| reversible reaction | A chemical reaction that can proceed in both the forward and reverse directions, with reactants forming products and products reforming reactants. |
| Term | Definition |
|---|---|
| concentrations at equilibrium | The molar amounts of reactants and products per unit volume when a reversible reaction reaches equilibrium and no net change occurs. |
| equilibrium constant expression | A mathematical expression that relates the concentrations or partial pressures of products and reactants at equilibrium, with each raised to the power of its stoichiometric coefficient. |
| Kc | The equilibrium constant expressed in terms of molar concentrations of reactants and products at equilibrium. |
| Kp | The equilibrium constant expressed in terms of partial pressures of gaseous reactants and products at equilibrium. |
| partial pressures | The individual pressure exerted by each gas in a mixture of gases at equilibrium. |
| Term | Definition |
|---|---|
| chemical species | A distinct chemical entity such as an atom, molecule, or ion that participates in a chemical reaction. |
| equilibrium concentrations | The concentrations of reactants and products when a reversible reaction reaches equilibrium and no further net change occurs. |
| equilibrium constant | A numerical value that expresses the ratio of products to reactants at equilibrium, indicating the extent to which a reaction proceeds. |
| proceeds to completion | A reaction that converts essentially all reactants to products, occurring when the equilibrium constant is very large. |
| Term | Definition |
|---|---|
| equilibrium constant | A numerical value that expresses the ratio of products to reactants at equilibrium, indicating the extent to which a reaction proceeds. |
| multistep process | A reaction mechanism consisting of two or more elementary steps that combine to produce an overall reaction. |
| overall equilibrium expression | The equilibrium constant expression for the net reaction obtained by adding multiple elementary steps together. |
| reaction quotient | A value calculated using the same expression as the equilibrium constant but using current (non-equilibrium) concentrations or partial pressures. |
| stoichiometric coefficients | The numerical coefficients in a balanced chemical equation that indicate the relative proportions of reactants and products. |
| Term | Definition |
|---|---|
| balanced reaction | A chemical equation in which the number of atoms of each element is equal on both sides of the equation. |
| chemical species | A distinct chemical entity such as an atom, molecule, or ion that participates in a chemical reaction. |
| concentration | The amount of solute dissolved in a given volume of solution, typically expressed in molarity or other units of amount per volume. |
| dynamic equilibrium | A state of equilibrium in which forward and reverse reactions continue to occur at equal rates, maintaining constant macroscopic properties. |
| equilibrium | The state in which the forward and reverse reaction rates are equal, resulting in constant concentrations or partial pressures of reactants and products. |
| equilibrium constant | A numerical value that expresses the ratio of products to reactants at equilibrium, indicating the extent to which a reaction proceeds. |
| forward reaction | The reaction pathway in which reactants are converted to products. |
| initial conditions | The starting concentrations or partial pressures of reactants and products before a reaction reaches equilibrium. |
| net consumption | The overall decrease in the amount of a substance as a result of a chemical reaction. |
| partial pressures | The individual pressure exerted by each gas in a mixture of gases at equilibrium. |
| reaction quotient | A value calculated using the same expression as the equilibrium constant but using current (non-equilibrium) concentrations or partial pressures. |
| reverse reaction | The reaction that proceeds from products back to reactants, opposite to the direction written in the balanced chemical equation. |
| Term | Definition |
|---|---|
| equilibrium | The state in which the forward and reverse reaction rates are equal, resulting in constant concentrations or partial pressures of reactants and products. |
| equilibrium constant | A numerical value that expresses the ratio of products to reactants at equilibrium, indicating the extent to which a reaction proceeds. |
| particulate model | A representation of matter showing individual atoms, molecules, or ions and their interactions to describe chemical processes at the molecular level. |
| product | Substances formed as a result of a chemical reaction. |
| reactant | Substances that are consumed in a chemical reaction to form products. |
| reversible reaction | A chemical reaction that can proceed in both the forward and reverse directions, with reactants forming products and products reforming reactants. |
| Term | Definition |
|---|---|
| chemical species | A distinct chemical entity such as an atom, molecule, or ion that participates in a chemical reaction. |
| dilution | The process of decreasing the concentration of a solute in a solution by adding solvent, which can shift equilibrium position. |
| equilibrium | The state in which the forward and reverse reaction rates are equal, resulting in constant concentrations or partial pressures of reactants and products. |
| external stress | A change applied to a system at equilibrium, such as addition or removal of a chemical species, temperature change, pressure change, or dilution. |
| Le Châtelier's principle | A principle stating that when a system at equilibrium is disturbed, the system shifts to counteract the disturbance and re-establish equilibrium. |
| pH | A logarithmic scale used to express the concentration of hydronium ions in a solution, calculated as −log[H3O+]. |
| pressure | The force exerted by gas molecules; changes in pressure of a gas-phase system can shift the equilibrium position. |
| temperature | A factor that influences reaction rate by affecting the kinetic energy and collision frequency of reactant molecules. |
| volume | The space occupied by a system; changes in volume of a gas-phase system can shift equilibrium position. |
| Term | Definition |
|---|---|
| buffer capacity | The amount of acid or base that a buffer solution can neutralize while maintaining a relatively constant pH. |
| buffer components | The conjugate acid-base pair that makes up a buffer solution and determines its pH and capacity. |
| concentration ratio | The ratio of the concentration of the conjugate base to the concentration of the conjugate acid, [A-]/[HA], in a buffer solution. |
| conjugate acid | The species formed when a base accepts a proton; the acid form in an acid-base conjugate pair. |
| conjugate base | The species formed when an acid donates a proton; the base form in an acid-base conjugate pair. |
| Term | Definition |
|---|---|
| autoionization | The process by which water molecules react with each other to produce hydronium and hydroxide ions in equilibrium. |
| hydronium ion | The aqueous ion H3O+(aq) formed when a hydrogen ion bonds with a water molecule; represents the form of hydrogen ion in aqueous solution. |
| hydroxide ion | The negatively charged ion OH− produced when water autoionizes or when a base dissolves in water. |
| Kw | The ion product constant for water, equal to [H3O+][OH−] = 1.0 × 10−14 at 25°C, representing the equilibrium constant for water autoionization. |
| neutral solution | An aqueous solution in which pH = pOH = 7.0 at 25°C, meaning the concentrations of hydronium and hydroxide ions are equal. |
| pH | A logarithmic scale used to express the concentration of hydronium ions in a solution, calculated as −log[H3O+]. |
| pKw | The negative logarithm of Kw; equals 14.0 at 25°C and represents the sum of pH and pOH in any aqueous solution at that temperature. |
| pOH | A logarithmic scale used to express the concentration of hydroxide ions in a solution, calculated as −log[OH−]. |
| Term | Definition |
|---|---|
| hydroxide ion | The negatively charged ion OH− produced when water autoionizes or when a base dissolves in water. |
| Le Châtelier's principle | A principle stating that when a system at equilibrium is disturbed, the system shifts to counteract the disturbance and re-establish equilibrium. |
| pH-sensitive solubility | The property of a salt's solubility changing in response to changes in pH of the solution. |
| salt solubility | The amount of a salt that can dissolve in a solution, which varies depending on pH when the salt contains weak acid, weak base, or hydroxide ions. |
| weak acid | An acid that only partially ionizes in solution, establishing an equilibrium between the molecular form (HA) and its conjugate base (A-). |
| weak base | A base that only partially dissociates in water; examples include ammonia and carboxylate ions. |
| Term | Definition |
|---|---|
| complete ionization | The process where all molecules of a strong acid or base separate into ions in aqueous solution. |
| conjugate base | The species formed when an acid donates a proton; the base form in an acid-base conjugate pair. |
| hydronium ion | The aqueous ion H3O+(aq) formed when a hydrogen ion bonds with a water molecule; represents the form of hydrogen ion in aqueous solution. |
| hydroxide ion | The negatively charged ion OH− produced when water autoionizes or when a base dissolves in water. |
| ionize | The process by which a compound separates into ions when dissolved in solution. |
| pH | A logarithmic scale used to express the concentration of hydronium ions in a solution, calculated as −log[H3O+]. |
| pOH | A logarithmic scale used to express the concentration of hydroxide ions in a solution, calculated as −log[OH−]. |
| strong acid | An acid that completely dissociates in water and has a very weak conjugate base; examples include HCl, HBr, HI, HClO₄, H₂SO₄, and HNO₃. |
| strong base | A base that completely dissociates in water and has a very weak conjugate acid; group I and II hydroxides are common examples. |
| Term | Definition |
|---|---|
| conjugate acid | The species formed when a base accepts a proton; the acid form in an acid-base conjugate pair. |
| conjugate base | The species formed when an acid donates a proton; the base form in an acid-base conjugate pair. |
| equilibrium | The state in which the forward and reverse reaction rates are equal, resulting in constant concentrations or partial pressures of reactants and products. |
| hydronium ion | The aqueous ion H3O+(aq) formed when a hydrogen ion bonds with a water molecule; represents the form of hydrogen ion in aqueous solution. |
| hydroxide ion | The negatively charged ion OH− produced when water autoionizes or when a base dissolves in water. |
| ionization | The process by which an acid or base separates into ions when dissolved in water. |
| Ka | The acid ionization constant that expresses the equilibrium between a weak acid and its conjugate base in water. |
| Kb | The base ionization constant that expresses the equilibrium between a weak base and its conjugate acid in water. |
| Kw | The ion product constant for water, equal to [H3O+][OH−] = 1.0 × 10−14 at 25°C, representing the equilibrium constant for water autoionization. |
| monoprotic weak acid | An acid that can donate one proton and only partially ionizes in water, establishing an equilibrium between the molecular acid and its conjugate base. |
| monoprotic weak base | A base that can accept one proton and only partially ionizes in water, establishing an equilibrium between the molecular base and its conjugate acid. |
| percent ionization | The percentage of weak acid or base molecules that ionize in solution, calculated from the equilibrium concentration of ions and the initial concentration of the acid or base. |
| pH | A logarithmic scale used to express the concentration of hydronium ions in a solution, calculated as −log[H3O+]. |
| pKa | The negative logarithm of the acid dissociation constant (Ka); used to compare the relative strength of weak acids and predict protonation state at different pH values. |
| pKb | The negative logarithm of the base dissociation constant (Kb); used to compare the relative strength of weak bases. |
| pKw | The negative logarithm of Kw; equals 14.0 at 25°C and represents the sum of pH and pOH in any aqueous solution at that temperature. |
| pOH | A logarithmic scale used to express the concentration of hydroxide ions in a solution, calculated as −log[OH−]. |
| un-ionized | The molecular form of a weak acid or base that has not separated into ions in solution. |
| Term | Definition |
|---|---|
| buffer solution | A solution containing a large concentration of both members of a conjugate acid-base pair that resists changes in pH when small amounts of acid or base are added. |
| conjugate acid | The species formed when a base accepts a proton; the acid form in an acid-base conjugate pair. |
| conjugate base | The species formed when an acid donates a proton; the base form in an acid-base conjugate pair. |
| equilibrium constant | A numerical value that expresses the ratio of products to reactants at equilibrium, indicating the extent to which a reaction proceeds. |
| equimolar | Containing equal numbers of moles of two or more substances. |
| excess reagent | The reactant that remains after a reaction has gone to completion, with the other reactant being completely consumed. |
| Henderson-Hasselbalch equation | An equation used to calculate the pH of a buffer solution based on the pKa of the weak acid and the ratio of conjugate base to weak acid concentrations. |
| major species | The chemical species present in significant concentrations in a solution. |
| strong acid | An acid that completely dissociates in water and has a very weak conjugate base; examples include HCl, HBr, HI, HClO₄, H₂SO₄, and HNO₃. |
| strong base | A base that completely dissociates in water and has a very weak conjugate acid; group I and II hydroxides are common examples. |
| weak acid | An acid that only partially ionizes in solution, establishing an equilibrium between the molecular form (HA) and its conjugate base (A-). |
| weak base | A base that only partially dissociates in water; examples include ammonia and carboxylate ions. |
| Term | Definition |
|---|---|
| acidic protons | The protons in a polyprotic acid that can be donated to other species. |
| analyte | The substance in a solution whose amount or concentration is being determined during a titration. |
| conjugate acid | The species formed when a base accepts a proton; the acid form in an acid-base conjugate pair. |
| conjugate acid-base pair | Two species that differ by one proton, where one is the acid form and the other is the base form of the same substance. |
| conjugate base | The species formed when an acid donates a proton; the base form in an acid-base conjugate pair. |
| equivalence point | The point in a titration where the analyte is completely consumed by the titrant in a quantitative reaction. |
| half-equivalence point | The point in a titration halfway to the equivalence point, where the concentrations of a conjugate acid-base pair are equal. |
| monoprotic acid | An acid that can donate one proton (hydrogen ion) per molecule. |
| pKa | The negative logarithm of the acid dissociation constant (Ka); used to compare the relative strength of weak acids and predict protonation state at different pH values. |
| polyprotic acid | An acid that can donate more than one proton (hydrogen ion) per molecule. |
| proton-transfer reaction | A chemical reaction in which a proton is transferred from one species to another. |
| strong acid | An acid that completely dissociates in water and has a very weak conjugate base; examples include HCl, HBr, HI, HClO₄, H₂SO₄, and HNO₃. |
| strong base | A base that completely dissociates in water and has a very weak conjugate acid; group I and II hydroxides are common examples. |
| titrant | A solution of known concentration that is added to an analyte during a titration to determine the amount of analyte present. |
| titration | An analytical procedure used to determine the amount of an analyte in solution by reacting it with a titrant of known concentration. |
| titration curve | A graph plotting pH versus the volume of titrant added during a titration, used to summarize titration results. |
| weak acid | An acid that only partially ionizes in solution, establishing an equilibrium between the molecular form (HA) and its conjugate base (A-). |
| weak base | A base that only partially dissociates in water; examples include ammonia and carboxylate ions. |
| Term | Definition |
|---|---|
| acid strength | The ability of an acid to donate protons, determined by the stability of its conjugate base; stronger acids more readily donate protons. |
| base strength | The ability of a base to accept protons, determined by the stability of its conjugate acid; stronger bases more readily accept protons. |
| carboxylate ion | The conjugate base of a carboxylic acid, formed when a carboxylic acid donates a proton; a common weak base. |
| carboxylic acid | A class of weak organic acids containing a carboxyl group (-COOH) that can donate a proton. |
| conjugate acid | The species formed when a base accepts a proton; the acid form in an acid-base conjugate pair. |
| conjugate base | The species formed when an acid donates a proton; the base form in an acid-base conjugate pair. |
| electronegativity | A measure of an atom's ability to attract valence electrons in a chemical bond; increases across a period and decreases down a group in the periodic table. |
| inductive effect | The stabilization or destabilization of a conjugate base through the withdrawal or donation of electron density by nearby atoms or groups. |
| molecular structure | The arrangement of atoms and bonds in a molecule that determines its chemical properties and reactivity. |
| resonance | The representation of a molecule using two or more equivalent Lewis structures that differ only in the placement of electrons, used to describe bonding when a single structure is inadequate. |
| stabilization | The process by which structural features such as electronegativity, inductive effects, or resonance make a conjugate base or conjugate acid more stable and less likely to reform the original acid or base. |
| strong acid | An acid that completely dissociates in water and has a very weak conjugate base; examples include HCl, HBr, HI, HClO₄, H₂SO₄, and HNO₃. |
| strong base | A base that completely dissociates in water and has a very weak conjugate acid; group I and II hydroxides are common examples. |
| weak acid | An acid that only partially ionizes in solution, establishing an equilibrium between the molecular form (HA) and its conjugate base (A-). |
| weak base | A base that only partially dissociates in water; examples include ammonia and carboxylate ions. |
| Term | Definition |
|---|---|
| acid-base indicator | A substance that exhibits different observable properties (such as color) depending on its protonation state, allowing it to signal pH changes in a solution. |
| conjugate acid | The species formed when a base accepts a proton; the acid form in an acid-base conjugate pair. |
| conjugate base | The species formed when an acid donates a proton; the base form in an acid-base conjugate pair. |
| deprotonated | The state of a molecule or ion after it has donated a proton (H+), decreasing its positive charge or increasing its negative charge. |
| equivalence point | The point in a titration where the analyte is completely consumed by the titrant in a quantitative reaction. |
| pKa | The negative logarithm of the acid dissociation constant (Ka); used to compare the relative strength of weak acids and predict protonation state at different pH values. |
| pKb | The negative logarithm of the base dissociation constant (Kb); used to compare the relative strength of weak bases. |
| predominant form | The chemical species (protonated or deprotonated) that exists in higher concentration in solution at a given pH. |
| protonated | The state of a molecule or ion after it has accepted a proton (H+), increasing its positive charge or decreasing its negative charge. |
| protonation state | The relative concentrations of the protonated (HA) and deprotonated (A-) forms of an acid or base in solution. |
| titration | An analytical procedure used to determine the amount of an analyte in solution by reacting it with a titrant of known concentration. |
| weak acid | An acid that only partially ionizes in solution, establishing an equilibrium between the molecular form (HA) and its conjugate base (A-). |
| weak base | A base that only partially dissociates in water; examples include ammonia and carboxylate ions. |
| Term | Definition |
|---|---|
| buffer solution | A solution containing a large concentration of both members of a conjugate acid-base pair that resists changes in pH when small amounts of acid or base are added. |
| conjugate acid | The species formed when a base accepts a proton; the acid form in an acid-base conjugate pair. |
| conjugate acid-base pair | Two species that differ by one proton, where one is the acid form and the other is the base form of the same substance. |
| conjugate base | The species formed when an acid donates a proton; the base form in an acid-base conjugate pair. |
| pH stabilization | The ability of a buffer solution to maintain a relatively constant pH despite the addition of small amounts of acid or base. |
| Term | Definition |
|---|---|
| buffer solution | A solution containing a large concentration of both members of a conjugate acid-base pair that resists changes in pH when small amounts of acid or base are added. |
| concentration ratio | The ratio of the concentration of the conjugate base to the concentration of the conjugate acid, [A-]/[HA], in a buffer solution. |
| conjugate acid-base pair | Two species that differ by one proton, where one is the acid form and the other is the base form of the same substance. |
| dissociation | The process by which a compound breaks apart into its constituent ions or molecules in solution. |
| equilibrium expression | A mathematical equation that relates the concentrations or partial pressures of reactants and products at equilibrium, expressed as Kc or Kp. |
| pH | A logarithmic scale used to express the concentration of hydronium ions in a solution, calculated as −log[H3O+]. |
| pKa | The negative logarithm of the acid dissociation constant (Ka); used to compare the relative strength of weak acids and predict protonation state at different pH values. |
| weak acid | An acid that only partially ionizes in solution, establishing an equilibrium between the molecular form (HA) and its conjugate base (A-). |
| Term | Definition |
|---|---|
| cell potential | The electrical potential difference between the anode and cathode of an electrochemical cell, which drives the spontaneous redox reaction. |
| concentration cell | An electrochemical cell in which the two half-cells contain the same chemical species but at different concentrations. |
| equilibrium | The state in which the forward and reverse reaction rates are equal, resulting in constant concentrations or partial pressures of reactants and products. |
| Le Châtelier's principle | A principle stating that when a system at equilibrium is disturbed, the system shifts to counteract the disturbance and re-establish equilibrium. |
| Nernst equation | The equation E = E° − (RT/nF) ln Q that relates cell potential to standard cell potential and the reaction quotient under nonstandard conditions. |
| nonstandard conditions | Electrochemical conditions where concentrations of active species differ from 1 M, pressures differ from 1 atm, or temperature differs from 25°C. |
| reaction quotient | A value calculated using the same expression as the equilibrium constant but using current (non-equilibrium) concentrations or partial pressures. |
| spontaneous electron flow | The natural movement of electrons from the anode to the cathode in an electrochemical cell driven by the cell potential. |
| standard cell potential | The cell potential (E°) measured under standard conditions where all concentrations are 1 M, pressure is 1 atm, and temperature is 25°C. |
| Term | Definition |
|---|---|
| dispersal of matter | The spreading out of particles over a larger volume, allowing them greater freedom of movement. |
| entropy change | The difference in entropy between the final and initial states of a system during a chemical or physical process. |
| kinetic energy distribution | The range and spread of energy values among particles in a system, which broadens as temperature increases. |
| kinetic molecular theory | A model explaining the behavior of gases based on the motion of particles and the distribution of kinetic energy among them. |
| moles of gas-phase products | The quantity of gaseous substances produced in a reaction, used to compare entropy changes in gas-phase reactions. |
| moles of gas-phase reactants | The quantity of gaseous substances that react in a chemical reaction, used to compare entropy changes in gas-phase reactions. |
| phase change | A transition between states of matter, such as from solid to liquid or liquid to gas. |
| Term | Definition |
|---|---|
| charge | A fundamental property of matter measured in coulombs (C), related to current and time by the equation I = q/t. |
| charge flow | The movement of electric charge through a circuit, measured in coulombs and related to current and time. |
| current | The flow of electrical charge through a circuit, measured in amperes. |
| electrochemical cell | A device consisting of electrodes and electrolyte solutions where redox reactions occur, either spontaneously (galvanic) or non-spontaneously (electrolytic). |
| electrode | A conductor through which electric current enters or leaves an electrochemical cell. |
| electrons transferred | The number of electrons moving from a reducing agent to an oxidizing agent during a redox reaction. |
| electroplating | An electrochemical process in which a metal is deposited onto an electrode through the reduction of metal ions. |
| Faraday's laws | Fundamental principles relating the amount of chemical change in an electrochemical cell to the quantity of electric charge passed through it. |
| ionic species | Charged particles (ions) that participate in electrochemical reactions and carry charge in solution. |
| oxidation-reduction reaction | A chemical reaction involving the transfer of one or more electrons between chemical species, indicated by changes in oxidation numbers. |
| stoichiometry | The quantitative relationship between reactants and products in a balanced chemical equation that determines the rates of change of their concentrations. |
| Term | Definition |
|---|---|
| absolute entropies | The total entropy of a substance at a given temperature and pressure, measured relative to zero entropy at absolute zero. |
| entropy change | The difference in entropy between the final and initial states of a system during a chemical or physical process. |
| standard entropy change | The change in entropy for a chemical or physical process under standard conditions, calculated as the difference between the absolute entropies of products and reactants. |
| standard molar entropies | The absolute entropy of one mole of a substance under standard conditions, typically used to calculate entropy changes in reactions. |
| Term | Definition |
|---|---|
| enthalpy | The total heat content of a system; at constant pressure, the enthalpy change equals the thermal energy transferred to or from the surroundings during a chemical or physical process. |
| entropy | A measure of the disorder or randomness in a system, including the dispersal of dissolved particles and reorganization of solvent molecules during dissolution. |
| Gibbs free energy change | The change in Gibbs free energy (ΔG°) for a chemical or physical process, measured under standard conditions, that indicates whether a process is thermodynamically favored. |
| standard Gibbs free energy of formation | The Gibbs free energy change (ΔG°f) when one mole of a substance is formed from its elements in their standard states. |
| standard state | The reference condition for a substance: pure substances, solutions at 1.0 M concentration, or gases at 1.0 atm (or 1.0 bar) pressure. |
| temperature dependence | The relationship between temperature and whether a process is thermodynamically favored, determined by the signs and magnitudes of ΔH° and ΔS°. |
| thermodynamically favored | A reaction or process that has a negative Gibbs free energy (ΔG < 0) and is spontaneous under given conditions. |
| Term | Definition |
|---|---|
| activation energy | The minimum energy required for reactants to overcome the energy barrier and proceed to products in a chemical reaction. |
| equilibrium | The state in which the forward and reverse reaction rates are equal, resulting in constant concentrations or partial pressures of reactants and products. |
| kinetic control | A situation where a thermodynamically favored process does not proceed at a noticeable rate due to a high activation energy barrier. |
| kinetics | The study of the rate at which a chemical reaction occurs and the factors that influence this rate. |
| measurable rate | A reaction rate that is fast enough to be observed and quantified within a reasonable time frame. |
| thermodynamically favored | A reaction or process that has a negative Gibbs free energy (ΔG < 0) and is spontaneous under given conditions. |
| Term | Definition |
|---|---|
| equilibrium constant | A numerical value that expresses the ratio of products to reactants at equilibrium, indicating the extent to which a reaction proceeds. |
| RT (gas constant × temperature) | The product of the universal gas constant and absolute temperature; used in the relationship between K and ΔG°. |
| standard conditions | The reference conditions (typically 25°C, 1 M concentration, 1 atm pressure) under which ΔG° and K are evaluated. |
| standard Gibbs free energy change | The change in free energy under standard conditions; negative values indicate thermodynamically favored processes that favor products. |
| thermodynamically favored | A reaction or process that has a negative Gibbs free energy (ΔG < 0) and is spontaneous under given conditions. |
| Term | Definition |
|---|---|
| dissolution | The process by which a solute dissolves in a solvent to form a solution, involving the breaking of bonds or interactions in the solute and formation of new interactions with the solvent. |
| enthalpy | The total heat content of a system; at constant pressure, the enthalpy change equals the thermal energy transferred to or from the surroundings during a chemical or physical process. |
| entropy | A measure of the disorder or randomness in a system, including the dispersal of dissolved particles and reorganization of solvent molecules during dissolution. |
| Gibbs free energy change | The change in Gibbs free energy (ΔG°) for a chemical or physical process, measured under standard conditions, that indicates whether a process is thermodynamically favored. |
| intermolecular interactions | Forces between molecules, such as hydrogen bonding, dipole-dipole forces, and London dispersion forces, that affect the physical and chemical properties of substances. |
| salt | An ionic compound formed from the reaction of an acid and a base. |
| solubility | The maximum amount of a solute that can dissolve in a given amount of solvent at a specific temperature, typically expressed in moles per liter (molarity) or grams per 100 mL of solvent. |
| solvent | The substance, typically a liquid, in which a solute dissolves to form a solution. |
| Term | Definition |
|---|---|
| ATP to ADP conversion | The hydrolysis of adenosine triphosphate to adenosine diphosphate, a thermodynamically favorable reaction that releases energy to drive unfavorable biological processes. |
| common intermediates | Shared chemical species or compounds that participate in multiple reactions within a coupled reaction system. |
| coupled reactions | Two or more reactions that share common intermediates, where a thermodynamically favorable reaction is linked to drive a thermodynamically unfavorable reaction forward. |
| electrolytic cell | An electrochemical cell in which electrical energy is used to drive a non-spontaneous redox reaction. |
| external source of energy | Energy supplied from outside a system to drive a process that would not occur spontaneously, such as electrical energy or light. |
| photosynthesis | The process by which light energy is used to drive the thermodynamically unfavorable conversion of carbon dioxide and water into glucose. |
| standard Gibbs free energy change | The change in free energy under standard conditions; negative values indicate thermodynamically favored processes that favor products. |
| thermodynamically unfavored | A reaction that does not proceed spontaneously under standard conditions, resulting in a negative cell potential and positive Gibbs free energy change. |
| Term | Definition |
|---|---|
| anode | The electrode where oxidation occurs in an electrochemical cell. |
| cathode | The electrode where reduction occurs in an electrochemical cell. |
| current | The flow of electrical charge through a circuit, measured in amperes. |
| electrochemical cell | A device consisting of electrodes and electrolyte solutions where redox reactions occur, either spontaneously (galvanic) or non-spontaneously (electrolytic). |
| electrode | A conductor through which electric current enters or leaves an electrochemical cell. |
| electrode mass | The mass of an electrode, which can change during electrochemical reactions due to oxidation or reduction at the electrode surface. |
| electrolytic cell | An electrochemical cell in which electrical energy is used to drive a non-spontaneous redox reaction. |
| electron flow | The movement of electrons through the external circuit of an electrochemical cell from the anode to the cathode. |
| galvanic cell | An electrochemical cell in which a spontaneous redox reaction generates electrical current. |
| half-cells | Individual compartments of an electrochemical cell, each containing an electrode and electrolyte solution where a half-reaction occurs. |
| half-reaction | Separate equations showing either the oxidation process (loss of electrons) or the reduction process (gain of electrons) in a redox reaction. |
| ion flow | The movement of ions through the electrolyte and salt bridge to complete the circuit in an electrochemical cell. |
| oxidation | The loss of electrons by a substance in a redox reaction. |
| reduction | The gain of electrons by a substance in a redox reaction. |
| salt bridge | A tube containing an inert electrolyte that connects two half-cells and allows ion flow to maintain electrical neutrality. |
| thermodynamically favored | A reaction or process that has a negative Gibbs free energy (ΔG < 0) and is spontaneous under given conditions. |
| thermodynamically unfavored | A reaction that does not proceed spontaneously under standard conditions, resulting in a negative cell potential and positive Gibbs free energy change. |
| Term | Definition |
|---|---|
| electrochemical cell | A device consisting of electrodes and electrolyte solutions where redox reactions occur, either spontaneously (galvanic) or non-spontaneously (electrolytic). |
| half-reaction | Separate equations showing either the oxidation process (loss of electrons) or the reduction process (gain of electrons) in a redox reaction. |
| oxidation half-reaction | The half-reaction in which a species loses electrons. |
| oxidation-reduction reaction | A chemical reaction involving the transfer of one or more electrons between chemical species, indicated by changes in oxidation numbers. |
| reduction half-reaction | The half-reaction in which a species gains electrons. |
| standard cell potential | The cell potential (E°) measured under standard conditions where all concentrations are 1 M, pressure is 1 atm, and temperature is 25°C. |
| standard Gibbs free energy change | The change in free energy under standard conditions; negative values indicate thermodynamically favored processes that favor products. |
| standard reduction potential | The voltage associated with a reduction half-reaction under standard conditions, used to calculate the overall cell potential. |
| thermodynamically favored | A reaction or process that has a negative Gibbs free energy (ΔG < 0) and is spontaneous under given conditions. |
| thermodynamically unfavored | A reaction that does not proceed spontaneously under standard conditions, resulting in a negative cell potential and positive Gibbs free energy change. |
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