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frame of reference

a system of objects that are not moving with respect to one another

relative motion

movement in relation to a frame of reference


the length of the path between two points


a quantity that has a direction associated with it

resultant vector

the vector sum of two or more vectors


the ratio of the distance an object moves to the amount of time the object moves

average speed

the total distance traveled divided by the time it takes to travel that distance

instantaneous speed

the rate at which an object is moving at a given moment in time


the speed and direction an object is moving, measured relative to a reference point


the rate at which velocity changes

free fall

the movement of an object toward Earth because of gravity

constant acceleration

a steady change in velocity

linear graph

a graph in which the displayed data form a straight line

nonlinear graph

a graph in which the displayed data form a curved line

periodic table

an arrangement of elements in columns, based on a set of properties that repeat from row to row


a row in a periodic table of elements


a column of elements in a periodic table

periodic table

an arrangement of elements in columns, based on a set of properties that repeat from row to row

atomic mass unit (amu)

one twelfth the mass of a carbon-12 atom


elements that are good conductors of heat and electric current

transition metals

elements that form a bridge between elements of the left and right sides of the periodic table


elements that are poor conductors of heat and electric current


elements with properties that fall between those of metals and nonmetals

valence electron

an electron that is in the highest occupied energy level of an atom

alkali metals

the elements in Group 1A of the periodic table, not including hydrogen

alkaline earth metals

the elements in Group 2A of the periodic table


the elements in Group 7A of the periodic table

noble gases

the elements in Group 8A of the periodic table


the dense, positively charged mass located in the center of an atom.


a positively charged subatomic particle that is found in the nucleus of an atom


a negatively charged subatomic particle; the space outside the nucleus


a neutral subatomic particle that is found in the nucleus of an atom

atomic number

a unique number for each element that equals the number of protons in an atom of that element

mass number

the sum of the protons and neutrons in the nucleus in the nucleus of that atom


atoms of the same element that have different numbers of neutrons and different mass numbers

energy levels

the possible energies that electrons in an atom can have

electron cloud

a visual model of the most likely locations for electrons in an atom


a region of space around the nucleus where an electron is most likely to be found

electron configuration

the arrangement of electrons in the orbitals of an atom

ground state

when all the electrons in an atom have the lowest possible energies


the state of matter in which materials have a definite shape and a definite volume


the state of matter in which a material has a definite volume but not a definite shape


the state of matter in which a material has neither a definite shape nor a definite volume

kinetic energy

the energy an object has due to its motion


the result of a force distributed over an area

absolute zero

a temperature of 0 kelvins

Charles's law

the direct proportion of the volume of a gas to its temperature (in kelvins) if the pressure and the number of particles of the gas are constant

Boyle's law

the inverse variation of the volume of a gas with its pressure if the temperature and the number of particles are constant

phase change

a reversible physical change that occurs when a substance changes from one state of matter to another


a description of a change in which a system absorbs energy from its surroundings

heat of fusion

the energy a substance must absorb in order to change from a solid to a liquid


a description of a change in which a system releases energy to its surroundings


the phase change in which a substance changes from a liquid to a gas

heat of vaporization

the energy a substance must absorb in order to change from a liquid to a gas


the process that changes a substance from a liquid to a gas at temperatures below the substance's boiling point

vapor pressure

the pressure caused by the collisions of particles in a vapor with the walls of a container


the phase change in which a substance changes from a gas or vapor to a liquid


the phase change in which a substance changes from a solid to a gas or vapor without changing to a liquid first


the phase change in which a gas or vapor changes directly into a solid without first changing into a liquid; the placement of sediment that has been transported from another location

pure substance

matter that always has exactly the same composition; an element or compound


a substance that cannot be broken down into simpler substances


the smallest particle of an element


a substance that is made from two or more simpler substances and can be broken down into those simpler substances

heterogeneous mixture

a type of mixture in which the parts of the mixture are noticeably diferent from one another

homogeneous mixture

a type of mixture in which the substances in the mixture are so evenly distributed that it is difficult to distinguish one substance in the mixture from another


when substances dissolve and form a homogeneous mixture


a heterogeneous mixture that separates into layers over time


contains some particles that are intermediate in size between the small particles in a solution and the larger particles in a suspension

physical property

any characteristic of a material that can be observed or measured without changing the composition of the substances in the material


the tendency of a liquid to keep from flowing


a material's abitlity to allow heat to flow


the ability of a solid to be hammered without shattering

melting point

the temperature at which a substance changes from solid to liquid

boiling point

the temperature at which a substance boils


a process that separates materials based on the size of their particles


a process that separates the substances in a solution based on their boiling points

physical change

occurs when some of the properties of a material change, but the substances in the material remain the same

chemical property

any ability to produce a change in the composition of matter


a material's ability to burn in the presence of oxygen


the property that describes how readily a substance combines chemically with other substances

chemical change

occurs when a substance reacts and forms one or more new substances


any solid that forms from a liquid mixture


a system of knowledge about the natural world and the methods used to find that knowledge


the use of scientific knowledge to solve practical problems


the study of the composition, structure, properties, and reactions of matter


the study of matter and energy and the interactions between the two through forces of motion


the study of the origin, history, and structure of the earth


the study of the universe beyond earth


the study of life and life processes

scientific method

an organized plan used for gathering, organizing, and communicating info


info obtained through the senses


a proposed answer to a question

manipulated variable

the variable that causes a change in another variable

responding variable

a variable that changes in response to a change in the manipulated variable

controlled experiment

an experiment in which only the manipulated variable is deliberately changed at a time

scientific theory

a well-tested explanation for a set of observations or experimental results

scientific law

a statement that summarizes a pattern found in nature


a representation of an object or event

scientific notation

a way of expressing a value as the product between a number of 1 and 10 and a power of 10


a straight-line distance between points


the amount of matter in an object


the amount of space taken up by an object


the ratio of a material's mass to its volume

conversion factor

a ratio of equivalent measurements that is used to convert a quantity from one unit to another


a gauge of how exact a measurement is

significant figure

all the digits in a measurement that are directly measured, plus the last digit, which is estimated


the closeness of a measurement to the true value of what is measured


an instrument that measures temperature


the steepness of a line, equal to the ratio of a vertical change to the corresponding horizontal change

direct proportion

a relationship between two variables in which their ratio is constant

inverse proportion

a relationship in which the product of two variables is a constant when all other variables are held constant

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