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Science Mid-term
review terms & concepts
81
Science
9th Grade
01/12/2012

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Term
science
Definition
a system of knowledge based on facts or principles
Term
technology
Definition
the application of science to meet human needs
Term
scientific theory
Definition
a tested, possible explanation of a natural event
Term
scientific law
Definition
a summary of an observed natural event
Term
scientific method
Definition
a series of logical steps to follow in order to solve problems
Term
critical thinking
Definition
applying logic and reason to observations and conclusions
Term
variable
Definition
anyhting that can change in an experiment
Term
length
Definition
the straight-line distance between any 2 points
Term
mass
Definition
measure of the quantity of matter in an object
Term
volume
Definition
a measure of space, such as the compacity of a container
Term
weight
Definition
the force with which gravity pulls on a quantity of matter
Term
scientific notation
Definition
a value written as a simple # multiplied by the power of 10
Term
precision
Definition
degree of exactness in a measurement
Term
significant figures
Definition
the digits in a measurement that are known with certainty
Term
accuracy
Definition
the extent to which a measurement approaches the true value
Term
chemistry
Definition
the study of matter and how it changes
Term
matter
Definition
anything that hs mass and occupies space
Term
element
Definition
a substance that cannot be broken down into a simpler substance
Term
atom
Definition
the smallest particlethat has the properties of an element
Term
compound
Definition
a substance made of atoms of more than one element bound together
Term
molecule
Definition
the smallest unit of a substance that exhibits all of the properties charcteristic of that substance
Term
chemical formula
Definition
the chemical symbols and numbers indicating the atoms contained in the basic unit of a substance
Term
pure substance
Definition
any matter that has a fixed composition and definite properties
Term
mixture
Definition
a combination of more than one pure substances
Term
miscible
Definition
describes 2 or more liquids that are able to dissolve into each other in various proportions
Term
immiscible
Definition
describes 2 or more liquids that do not mix into each other
Term
homogeneous
Definition
mixture the same throughout
Term
heterogeneous
Definition
mixture where the substances aren't uniformly formed
Term
solute
Definition
the dissolved substance in a solution
Term
solvent
Definition
the dissolving medium in a solution
Term
solution
Definition
a homogeneous mixture of 2 or more substances uniformly spread throughout a single phase
Term
colloid
Definition
a mixture of very tiny particles of pure substances that are dispersed in another substance but do not settle out of the substance
Term
suspension
Definition
a mixture that looks uniform when stirred or shaken that seperates into different layers when it is no longer agitated
Term
solid
Definition
definate shape, definate volume
Term
liquid
Definition
no definate shape, definate voliume
Term
gas
Definition
no definate shape or volume
Term
pressure
Definition
the force exerted per unit area of a surface
Term
energy
Definition
the ability to change or move matter
Term
viscosity
Definition
the resistance of a fluid to flow
Term
evaporation
Definition
the change of a substance from a liquid to gas
Term
condensation
Definition
the change of a substance from a gas to a liquid
Term
sublimation
Definition
the change of a substance from a solid to a gas
Term
chamical property
Definition
the way a substance reacts with others to form new substances with different properties
Term
reactivity
Definition
the ability of a substance to combine chamically with another substance
Term
physical property
Definition
a characteristic of a substance that can be observed or measured without changing the composition of the substance
Term
melting point
Definition
the temp at which a solid becomes a liquid
Term
boiling point
Definition
the temp at which a liguid becomes a gas
Term
density
Definition
the mass per unit volume of a substance
Term
bouyancy
Definition
the force with which a more dense fluid pushes a less dense substance upward
Term
chemical change
Definition
a change that occurs when a substance changes composition by forming one or more new substances
Term
physical change
Definition
a change in the physical form or properties of a substance that occurs without a change in composition
Term
nucleus
Definition
the center of an atom; made up of protons and neutrons
Term
proton
Definition
a positively charged subatomic particle in the nucleus of an atom
Term
neutron
Definition
a neutral subatomic particle in the nucleus of an atom
Term
electron
Definition
a tiny negatively charged subatomic particle moving around outside the nucleus of an atom
Term
energy level
Definition
any of the possible energies an electron may have in an atom
Term
orbital
Definition
a region in the atom where there is a high probability of finding electrons
Term
valence electron
Definition
an electron in the outermost energy level of an atom
Term
periodic law
Definition
properties of elements tend to change in a regular pattern when elements are arranged in order of increasing atomic number, or number of protons in their atoms
Term
priod
Definition
a horizontal row of elements in the periodic table
Term
group(family)
Definition
a vertical column of elements in the periodic table
Term
ionization
Definition
the process of adding electrons to or removing electrons from an atom or group of atoms
Term
ion
Definition
an atom or group of atoms that has lost or gained one or more electrons and therefore has a net electric charge
Term
cation
Definition
an ion with a postitive charge
Term
anion
Definition
an ion with a negative charge
Term
atomic number
Definition
the # of protons in the nucleus of an atom
Term
mass number
Definition
the total # of protons and neutrons in the nucleus of an atom
Term
isotope
Definition
any atoms having the same # of protons but different #s of neutrons
Term
atomic mass unit(amu)
Definition
a quantity = to 1/12 of the mass of a carbon-12 atom
Term
average atomic mass
Definition
the weighted average of the masses of all naturally occuring isotopes of an element
Term
metals
Definition
the elements that are good conductors of heat and electricity
Term
nonmetals
Definition
the elements that are usually poor conductors of heat and electricity
Term
semiconductors
Definition
the elements that are intermediate conductors of heat and electricity
Term
alaki metals
Definition
the highly reactive metallic elements located in group 1A of the periodic table
Term
alakine-earth metals
Definition
the reactive metallic elements located in group 2A
Term
transition metals
Definition
the metallic elements located in all the B's of the periodic table
Term
halogens
Definition
the highly reactive elements located in group 7A
Term
noble gases
Definition
the unreactive gaseous elements located in group 8A
Term
Democritus
Definition
came up with the idea that atoms exist during B.C. and couldn't prove
Term
Dalton
Definition
atomic theory that *elements are made of tiny unique particles called atoms *atoms of the same element are exactly alike *atoms of different elements can join to form molecules
Term
Bohr's model
Definition
exactly like the modern model except he said electrons orbit specific paths, but they don't
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