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chem midterm

midterm vocab

TermDefinition
chemistry Study of the composition and properties of substances, and the changes those substances can undergo
scientific method Orderly and systematic approach to gathering info in order to answer questions about the world
observation Fact that is noticed either quantitatively or qualitatively
hypothesis Proposition and unproved explanation of observed facts (educated guess)
experiment Carefully devised procedure for making observations and gathering data
conclusion Judgement or opinion formed as a result of analyzing data
natural law Description of a phenomenon that has been repeatedly and uniformly observed in nature
theory Logical and time tested explanation of a phenomenon that occurs in the natural world
variable Factor being tested In an experiment
experimental control Factor that remains constant during an experiment
metric system Decimal system of measurement used internationally
international system of units (SI) System of units that is an extension of the metric system; includes 7 base units
base unit One of seven units used in the SI system
mass Quantify of matter in a unit
derived unit Unit in the SI system that results in a combination of base units
volume Amount of space that an object occupies
metric prefix Syllable or group of syllables attached to the beginning of a metric unit in order to make the unit larger or smaller
precision Measure of the agreement between the numerical values of two or more measurements that have been using the same method; when the same values result from repeated measurements, the measurements are said to have high ______
accepted value Standard value for a measurement
accuracy Indicates how close a measurement is to it's accepted value
significant digit Digit in the measurement that is certain, plus one digit that is estimated
percent error Relative error as determined by finding the difference between an accepted value an d a measured value, dividing the result by the accepted value and multiplying the quotient by 100
density Mass of an object divided by its volume
dimensional analysis Technique for converting between units by using the numerical relationships between the units by using the numerical relationships between the units
unit equality Equation that shows the numerical relationships between 2 units
conversion factor Fraction having a value of one that is written from a unit equality and is used to change a measurement from one unit to another
energy Capacity to do work or transfer heat
kinetic energy Energy of motion
potential energy Stored energy or energy of position
joule Basic unit of energy
law of conservation of energy Natural law describing the fact that energy is neither created nor destroyed in any process
kelvin scale S.I temperature scale with a zero point of absolute zero
absolute zero Theoretically lowest temperature that can be reached -273.15 C or 0 K
matter Anything that has mass and volume
solid State at which matter holds a definite shape and volume
liquid State in which matter does not hold a definite shape but does occupy a definite volume
gas State in which matter doesn't have a definite shale or volume
physical property Characteristic of a substance that can be observed without altering the identity of the substance
chemical property Characteristic of a substance that can't be observed without altering the identity of the substance
physical change Process by which a substance undergoes a change that does not alter its identity
chemical change Process by which the composition and properties of a substance change, thus altering the identity of the substance. Products a new substance
Avogadro's number 6.02 x 10*23
element Substance that can't be separated into a similar substance by a chemical change
compound Substance that contains two or more elements chemically combined
pure substance Substance made of one kind of material with a unique set of chemical and physical properties
mixture Blend of two or more pure substances that are not chemically combined
heterogeneous mixture Mixture in which the particles are not uniformly intermingled and that therefore has visibly different parts
homogeneous mixture Mixture in which the particles are uniformly intermingled and that therefore doesn't have visibly different parts
atom Smallest particle of an element that retains the chemical identity of that element
law of constant composition Natural law describing the fact that a given compound always contains the same elements in the same properties
atomic theory of matter Proposed by john dalton. States that atoms are neither created nor destroyed in a chemical reaction, all atoms of the same element are identical but not to other atoms
cathode ray Stream of electrons emitted by a negatively charged electrode and attracted by a positively charged electrode
cathode ray tube Evacuated glass tube in which a stream of electrons emitted by a cathode strikes a fluorescent material causing it to glow
electron Negatively charged particle in an atom
radioactivity Spontaneous emission of radiation from an atom
nucleus Concentrated core of an atom, which contains protons and neutrons
proton Positively charged particle in the nucleus of an atom
neutron Neutral particle in the core of an atom
atomic number Number of protons in the nucleus
atomic mass unit Unit by which the mass of an atom or the atomic particle is expressed.
ion Atom or group of atoms that has a positively or negative charge because it has lost or gained electrons
isotope Atom that has the same number of protons as another atom but has a different number of neutrons
mass number Sum of the number of protons and neutrons in the nucleus of an atom
atomic mass Weighted average of the masses of the existing isotopes of an element
nuclear reaction Process that changes the composition of the nucleus of an atom
strong nuclear force Attractive force between the particles in the nucleus. In a stable atom, it overcomes the force of repulsion
radioactive decay Spontaneous breakdown of an unstable atomic nucleus
nuclear equation Equation that describes the changes that occur during radioactive decay
Created by: hannahorth98