 | Term | Definition |
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Matter |
anything that takes up space and has mass |
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Mass |
the amount of matter that an object contains |
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Substance |
a sample of matter having a uniform and definite composition |
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Physical property |
a quality or condition of a substance that can be seen without changing composition |
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Solid |
matter that has a definite shape and volume |
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Liquid |
state of matter that flows, has a fixed volume, and takes the shape of its container |
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Gas |
matter that has no definite shape or volume; it adopts the shape of its container |
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Vapor |
a substance in the gaseous state that is ordinarily a liquid or solid at room temperature |
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Physical change |
a change that alters a given material without changing its composition |
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Mixture |
a physical blend of two or more substances |
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Heterogeneous mixture |
a mixture that is not uniform in composition |
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Homogeneous mixture |
a mixture completely uniform in composition |
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Solutions |
a homogeneous mixture |
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Phase |
any part of a system with uniform composition and properties |
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Distillation |
a purification process in which a liquid is evaporated and then condensed again to a liquid |
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Element |
the simplest form of matter that can exist under normal laboratory conditions |
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Compound |
substances that can be separated into simpler substances by chemical means |
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Chemical symbol |
a one or two letter representation of an element |
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Chemical reaction |
one or more substances are changed to new substances |
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Reactants |
the starting substances in a chemical reaction |
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Products |
the substances formed in a chemical reaction |
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Chemical property |
the ability of a substance to undergo a chemical reaction and to form new substances |
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Law of conservation of mass |
states mass cannot be created nor destroyed in a reaction or change |
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Atom |
the smallest particle of an element that retains properties of that element |
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Electron |
negatively charged subatomic particles |
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Cathode ray |
a stream of electrons produced at the negative electrode containing a gas at low pressure |
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Protons |
a positively charged subatomic particle located in a nucleus |
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Neutrons |
a neutrally charged subatomic particle that is located in a nucleus |
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Nucleus |
the central core of an atom |
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Atomic number |
the number of protons in the nucleus of an atom |
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Mass number |
the total number of protons and neutrons of an atom |
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Isotopes |
atoms that have the same number of protons but different numbers of neutrons |
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Atomic mass unit (amu) |
1/12 the mass of carbon-12 |
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Atomic mass |
the weighted averages of the masses of the isotopes of an element |
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Periodic table |
an arrangement of elements into rows and columns based on similarities in their properties |
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Periods |
horizontal rows of elements in the periodic table |
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Periodic law |
there is a periodic repetition of properties, when elements are arranged by atomic number |
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Group |
a vertical column in the periodic table |
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Representative elements |
Group a elements, because they have a wide range of properties |
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Metals |
part of Group A that have high electrical conductivity and a high luster when clean |
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Alkali metals |
Consists of Group 1A |
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Alkaline earth metals |
Consists of Group 2A |
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Transition metals |
Most of Group B |
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Inner transition metals |
atomic numbers 57-70 and 89-102 |
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Nonmetals |
elements that are generally nonlustrous and are generally poor conductors of electricity |
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Halogens |
the nonmetals of Group 7A |
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Noble gases |
Nonmetals of Group 0 that undergo few chemical reactions |
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Metalloids |
elements with properties intermediate between metals and nonmetals |
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Radioisotopes |
unstable isotopes |
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Radioactivity |
the process by which unstable atomic nuclei achieve stability |
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Radiation |
the penetrating rays and particles emitted by a radioactive source |
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Radioactive decay |
the spontaneous emission of radiation by an unstable nucleus |
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Alpha radiation |
consists of helium nuclei that have been emitted from a radioactive source |
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Alpha particles |
the particles emitted from alpha radiation that contain 4 protons and 2 neutrons |
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Beta radiation |
the emission of fast moving electrons from a radioactive source |
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Beta particles |
the fast moving particles with 0 protons that are negatively charged and have a -1 subscript |
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Gamma radiation |
high energy electromagnetic radiation |
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Band of stability |
a region where the nuclei are stable on a plot |
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Positron |
a particle with the mass of an electron but a charge of positive 1 |
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Half Life |
the time required for one-half of the nuclei of a radioisotope to decay to products |
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Transmutation |
the conversion of an atom of one element to an atom of another element |
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Transuranium elements |
the elements in the periodic table with atomic numbers above 92 |
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Fission |
the splitting of a nucleus into smaller fragments |
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Neutron moderation |
a process to reduce the speed of neutrons so that the reactor fuel can capture them |
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Neutron absorption |
a process that decreases the number of slow moving neutrons |
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Fusion |
occurs when nuclei combine to produce a nucleus of greater mass |
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Molecule |
the smallest electrically neutral substance that still has the properties of the substance |
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Molecular compound |
compounds composed of molecules |
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Ion |
atoms or groups of atoms that have a positive or negative charge |
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Cation |
any atoms or group of atoms that has a positive charge |
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Anion |
atoms or groups of atoms that have negative charges |
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Ionic compound |
compounds composed of cations and anions |
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Chemical formula |
shows the kinds and numbers of atoms in the smallest unit of the substance |
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Molecular formula |
shows the kinds and numbers of atoms present in a molecule of a compound |
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Formula unit |
the lowest whole number ratio of ions in a compound |
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Law of definite proportions |
states masses in a compound is always proportional |
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Law of multiple proportions |
ratios of masses is in whole numbers if 1+ compound is formed |
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Polyatomic ion |
tightly bound groups of atoms that behave as a unit and carry a charge |
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Mole (mol) |
the amount of a substance that contains 6.02 x 1023 representative particles of that substance |
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Avogadro’s number, 6.02 x 1023 |
the # of representative particles contained in one mole of a substance |
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Molar mass |
a general expression used to refer to the mass of a mole of any substance |
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STP (standard temperature and pressure) |
the conditions when the volume of a gas is usually measured |
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Molar volume |
the volume occupied by 1 mole of a gas at STP (22.4 L) |
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Percent composition |
the percent by mass of each element in a compound |
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Empirical formula |
a formula with the lowest whole-number ratio of elements in a compound |
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Chemical equation |
an expression representing a chemical reaction |
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Skeleton equation |
a chemical equation that does not indicate the relative amounts involved in the reaction |
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Catalyst |
a substance that speeds up the rate of a reaction but is not used up in the reaction |
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Coefficient |
a small whole number that appears in front of a formula in a balanced chemical equation |
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Combination reaction |
a reaction where two or more substances combine to form a single one |
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Decomposition reaction |
a single compound is broken down into two or more products |
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Single replacement reaction |
one element replaces a second element in a compound |
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Double replacement reaction |
an exchange of positive ions between two reacting compounds |
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Combustion reaction |
an element or a compound reacts with oxygen, often producing energy |
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Activity series of metals |
lists metals in order of decreasing reactivity |
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Complete ionic equation |
an equation that shows dissolved ionic compounds as their free ions |
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Net ionic equation |
the equation that indicates only those particles that actually take part in the reaction |
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Spectator ions |
ions that are not directly involved in a chemical reaction |
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Limiting reagent |
limits or determines the amount of product that can be formed in a reaction |
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Excess reagent |
the reactant that is not completely used up |
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Theoretical yield |
the maximum amount of product that can be formed from any given amount of reactants |
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Actual yield |
the amount of product that actually forms when the reaction is carried out |
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Percent yield |
the ratio of the actual yield to the theoretical yield expressed as a percent. |
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Kinetic energy |
the energy an object has because of its motion |
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Kinetic theory |
states tiny particles are in constant motion |
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Gas pressure |
the force exerted by a gas per unit surface area of an object |
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Vacuum |
an empty space with no particles and no pressure |
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Atmospheric pressure |
results from the collision of air molecules with an object |
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Barometers |
devices commonly used to measure atmospheric pressure |
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Pascal (Pa) |
the SI unit of pressure |
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Standard atmosphere (atm) |
the pressure required supporting 760 mm of mercury in a mercury barometer at 25°C |
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Vaporization |
the conversion of a liquid to a gas or vapor |
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Evaporation |
molecules from the surface break away and enter the gas or vapor state |
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Vapor pressure |
force due to the gas above a liquid |
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Boiling point |
the temperature at which the vapor pressure of the liquid is equal to external pressure |
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Normal boiling point |
the boiling point of a liquid at 101.3 kPa |
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Melting point |
the temperature at which a solid turns into a liquid |
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Crystal |
a substance in which the atoms, ions, or molecules are arranged in a pattern called a crystal lattice |
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Unit cell |
the smallest group of particles within a crystal that retain the geometric shape of the crystal |
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Allotrope |
two or more different molecular forms of the same element in the same physical state |
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Amorphous solid |
solids that lack internal structure |
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Glass |
transparent fusion products of inorganic substances that have cooled to a rigid state without crystallizing |
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Phase diagram |
gives the condition of temperature and pressure at which a substance exists as a solid, liquid, and gas |
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Triple point |
the only set of conditions where all three phases can exist in equilibrium with each other |
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Sublimation |
the change of a substance from a solid to vapor without passing through the liquid state |
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