Chemistry Glossary
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A
absolute zero - zero on the Kelvin temperature scale; equivalent to -273ºC; all molecular motion stops
accepted value - a quantity that is generally agreed upon by the scientific community
accuracy - how close a measurement is to the true value of the measurement
atom - the smallest particle of an elemnt that retains the properties of that element
atomic mass - the average of the mass of the isotopes of an element
atomic mass unit (amu) - unit of mass equal to one-twelfth the mass of the carbon-12 atom
atomic number - the number of protons in the nucleus of an atom of an element
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B
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C
cathode ray - a stream of electrons produced at the negative electrode (cathode) of a tube containing gas at low pressure
Celsius scale - temperature scale on which the freezing point of water is 0ºC and the boiling point is 100ºC
chemistry - the study of the composition of matter and the changes it undergoes
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D
Dalton's atomic theory - first theory to relate chemical changes to events at the atomic level
- elements are made of composed of tiny indivisible particles called atoms
- atoms of the same element are identical. atoms of one element are different from those of all other elements
- atoms of different elements can physically mix or can chemically combine in simple whole number ratios to form compounds
- chemical reactions occur when atoms are separated, joined, or rearranged; atoms cannot change from one element to another due to a chemical reaction
density - the ratio of the mass of an object to its volume
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E
electron - a negatively charged subatomic particle
error - the difference between the accepted value and the experimental value
experimental value - a quantitative value measured during an experiment
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F
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G
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H
hypothesis - a proposed explanation for observations
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I
isotopes - atoms of the same element with the same atomic number but different atomic masses because of different numbers of neutrons
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J
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K
Kelvin scale - the temperature scale in which the freezing point of water is 273K and the boiling point is 373K; 0K is absolute zero
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L
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M
mass - the amount of matter an objet contains
mass number - the total number of protons and neutrons in the nucleus of an atom
matter - anything that has mass and occupies space
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N
neutron - a subatomic particle with no charge and a mass of 1 amu; located in the nucleus of an atom
nucleus - the dense central part of atom; contains the protons and neutrons
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O
observation - information achieved through the senses
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P
percent error - the percent that the a measured value differs from the accepted value
precision - the closeness, or reproducibility, of measurements taken under the same conditions
proton - a positively charged subatomic particle found in the nucleus of an atom
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Q
qualitative measurement - a measurement that gives a descriptive, non-numeric result
quantitative measurement - a measurement that gives a definitive result; usually uses numbers
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R
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S
scientific law - a concisie statement that summarizes the results of many observations and experiments
scientific method - a method of inquiry, involving observations, experiments, hypotheses, and broad explanations called theories
significant figures - all the digits that can be known precisely in a a measurement plus a last estimated digit
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T
theory - a well tested model that explains why experiments give certain results
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U
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V
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W
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X
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Y
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Z
