Glossary of 1st Semester Chemistry Exam

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smallest particle of an element that can enter into chemical change & retains the properties of that element
the exact mass of an atom
atomic mass
a unit of mass equal to exactly 1/12 the mass of a carbon-12 atom
atomic mass unit
the number of protons in the nucleus of an atom of an element
atomic number
an instrument used to measure atmospheric pressure
turbulence in a liquid caused by the rapid formation of bubbles of vapor at the boiling point
substance that changes the speed of a chemical reaction without being permanently altered itself
an ion carrying a positive charge
a condensed statement that uses formulas to show the reactants & products in a chemical change
chemical equation
an action that produces a chemical change
chemical reaction
a substance of definite composition, which may be decomposed into two or more simpler substances by chemical change
shows the number & type of atoms of a substance
chemical formula
substance formed in a chemical reaction
a solid consisting of plane faces & having a definite shape. the atoms are arranged in a repeated pattern
mass per unit volume
The process in which a liquid is evaporated
The formula showing the simplest ration in which the atoms combine to form a compound
The escape of molecules from a liquid into the gaseous phase
Proposed explanation of observed facts or events, it is subjected to confirmation by further observations & experimentation
at atom or a group of atoms with an excess positive or negative charge
atoms of the same element having different mass numbers due to the different number of neutrons in their nuclei
the theory that explains the properties of matter in terms of molecular motion
kinetic theory
the total number of protons & neutrons in the nucleus of an atom
mass number
an association of two or more substances that are not chemically combined
the volume occupied by a gram, molecular mass of a gas or vapor. this volume is 22.4 liters at standard conditions
molar volume
the Avogadro number of any particle of definite composition. quantity of a substance that has a mass in gram numerically equal to its molecular mass
a formula that indicates the actual number of atoms of each element in one molecule of a substance
molecular formula
the mass of a molecule in atomic mass units
molar mass
the SI unit of pressure
a change in which the composition & chemical properties of a substance are not altered
physical change
a characteristic of a material that can be observed without a chemical change taking place
physical properties
a particle made up of two or more elements that carries a net electrical charge & acts as a unit in chemical change. the bonds between the atoms of the ion are covalent. sometimes called an ionic radical.
polyatomic ion
a measure of the agreement between the numerical values of two or more measurements that have been made using the same methods
one of the starting substances involved in a chemical reaction
statement of a relationship between observed facts. it may be a qualitative statement of a mathematical formula
scientific law
the ration of the mass of a given volume of a substance to that of an equal volume of a standard. water is the standard for liquids & solids; hydrogen, oxygen, or air may be used for gases
specific gravity
the name given to the study of the quantitative relationships that can be derived from formulas & equations
the change of a solid to a vapor(or the reverse) without passing through the liquid phase
is a broad & extensively tested explanation of why experiments give certain results. can never be proved because it is always possible for a new experiment to disprove it
scientific theory
the first theory to relate chemical changes to events at the atomic level. all elements are composed of tiny indivisible particles called atoms
Dalton's atomic theory
first suggested the existence of particles, he called atoms
proposed atom is mostly empty space, all positive charges & almost all the mass are concentrated in a small region called the nucleus
stated by Dalton; whenever two elements form more than one compound, the different masses of one element that combine with the same mass of the other element are in the ratio of small whole numbers
Law of Multiple Proportions
states that in samples of any chemical compound, the masses of the elements are always in the same proportions. if atoms combine in simple whole number ratios, their proportions by mass must always be the same
Law of Definite Proportions
compounds composed of molecules
molecular compounds
compounds composed of cations & anions; usually composed of metal cations & nonmetal anions
ionic compounds
a chemical equation, which mass, is conserved; each side of the equation has the same number of atoms of each element
balanced equation
a chemical equation that does not indicate the relative amounts of reactants & products
skeleton equation
limits or determines the amount of product that can formed in a reaction
limiting reagent
reactant that is not completely used up in a reaction
excess reagent
is the ratio of the actual yield to the theoretical yiels; measures the efficiency of the reaction. should not be larger than 100%
percent yield
the optically transparent fusion product of inorganic material that have cooled to a rigid state without crystallizing
the smallest group of particles within a crystal that retains the geometric shape of the crystal
unit cell
the forces that hold molecules together & are weak in liquids & covalent compopunds
intermolecular forces
kinetic energy is transferred without loss from one particle to another, and the total kinetic energy remains constant
elastic collisions
the amount of product that could form during a reaction calculated from a balanced chemical equation
theoretical yield
the amount of product that forms when a reaction is carried out in the lab
actual yield
state in which matter exist at very high temperatures involved in fusion, high-energy state in which ions exist in a gas like form. no known structural material can withstand the hot, corrosive condition of this state. magnetic fields are experiments in

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