international system of units, aka metric system, with units such as meter, second, mole, degrees C/K, etc.
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mass
measure of the quantity of matter in object
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weight
measure of the force that gravity exerts upon an object
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conversion factor
a ratio between equivalent units for use in dimensional analysis
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accuracy
describes how close a measurement is to the true value
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precision
describes the degree to which repeated measures of a value are similar or different
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significant figures
digits that represent the precision of the meausring device(s)
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scientific method
make observations, develop a hypothesis, test the hypothesis, analyze results, make a conclusion
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independent variable
the variable that is manipulated (x)
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dependent variable
a variable based on the independent variable (y)
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theory
a well-founded explanation for a phenomenon based on repeated observations
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law
an essentially confirmed fact that reconciles the results of all experiments relating to and observations of a phenomenon
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matter
any substance that has mass and takes up space
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volume
the three-dimensional space an object takes up
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physical property
a characteristic of matter that can be inherently observed without changing its chemical composition
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extensive property
a property that depends on the amount of matter
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intensive property
a property that is constant regardless of the amount of matter
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chemical property
the ability of a substance to be subject to a certain chemical change
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states of matter
solid, liquid, gas, plasma
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physical change
a change in which the properties of a substance change but its chemical composition does not
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chemical change
a change in which the chemical composition of the substance changes, or more substances are formed
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law of conservation of mass
mass is not created nor destroyed; the mass of a reaction's products is equal to that of its reactants
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mixture
a physical blend of two or more substances
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heterogeneous mixture
a mixture in which components are not uniformly mixed
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homogeneous mixture
a solution, in which all components are dissolved
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element
simplest form of matter that retains its own properties
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compound
chemical combination of elements
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pure substance
matter whose components cannot be separated physically (unlike in mixtures)
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law of definite proportions
the proportions of the masses of elements in a compound remain constant regardless of the size of the compound
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indicators of a chemical reaction
formation of gas, change in color or odor, release of energy (heat or light), formation of a precipitate
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precipitate
the insoluble solids formed as a result of a chemical reaction between two solutions
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reactants
materials going into a reaction (left side of arrow)
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yield
arrow in chemical equation
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products
materials produced by a reaction (right side of arrow)
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chromatography
a method used to separate the dyes of a mixture; a physical change occurs, in which soluble dyes move quickly up the paper and less soluble dyes move less quickly
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thermochemistry
the study of the changes substances undergo in chemical reactions (chemical changes) and changes in state (phase changes)
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temperature
the AVERAGE kinetic energy of particles in a thermochemical system
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heat
the TOTAL kinetic energy of particles in a thermochemical system
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thermoconductivity
the rate at which heat is transferred from one object to another
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heat capacity
the amount of heat required to raise the temperature of a substance by 1 degree C
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specific heat capacity
the amount of heat required to raise the temperature of 1 GRAM of a substance by 1 degree C
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endothermic process
a process that absorbs heat from the surroundings, causing the them to feel cold (Q\>0)
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exothermic process
a process that releases heat into the surroundings, causing them to feel warm (Q
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enthalpy
the heat released or absorbed by a chemical reaction
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phase changes
heat of fusion (solid-liquid), heat of solidification (liquid-solid), heat of vaporization (liquid-gas), heat of condensation (gas-liquid)
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enthalpy curve
a graph of phase changes and changes in temperature as a function of heat energy
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energy
the ability to do work or produce heat
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calorimetry
measures the amount of heat absorbed or released
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entropy
the measure of the disorder or randomness of the particles that make up a system
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average atomic mass
weighted average of the atomic masses of all naturally occurring isotopes of an element
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half-life
the time required for half of the nuclei of a radioactive substance to decay
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radioisotope
radioactive isotopes
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Henri Becquerel
experimented with uranium salts and showed that they emitted radiation
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Marie and Pierre Curie
coined the term radioactivity
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alpha decay
loss of a helium nuclei (2P 2N); -2 atomic number, -4 atomic mass; low penetrating power; +2 charge
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beta decay (negative)
neutron turns into a proton and an electron, which is emitted; +1 atomic number, no change in atomic mass; medium penetrating power, -1 charge
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positron emission
proton turns into a neutron and an positron, which is emitted; -1 atomic number, no change in atomic mass; medium penetrating power, +1 charge
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electron capture
an electron is drawn into the nucleus and combines with a proton to become a neutron which is emitted; -1 atomic number, no change in atomic mass; medium penetrating power, -1 charge
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gamma emission
a gamma ray is emitted; no change in atomic number or mass; extreme penetrating power, 0 charge
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transuranium element
elements made in particle accelerators; all elements over 93
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uses of nuclear reactions
timekeeping, power, dating
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proton
an atomic particle in the nucleus with a charge of +1 and a mass of 1 amu
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neutron
an atomic particle in the nucleus with a charge of 0 and a mass of 1 amu
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electron
an atomic particle orbiting the nucleus with a charge of -1 and a mass of ~1/1840 amu
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nucleus
the small, dense, positively charged center of the atom
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fission
the process which occurs when a heavy nucleus is bombarded with atomic particles and splits as in a nuclear bomb, releasing large amounts of energy
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fusion
the process which occurs in nature at temperatures of over 40 million degrees C when light nuclei are smashed together and fuse, releasing more energy than fission
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alpha particle
a helium nucleus (2P 2N)
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positron
an electron with a positive charge
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atomic number
the number of protons in the nucleus of an atom
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atomic mass/mass number
the sum of the protons and neutrons in the nucleus of an atom
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Ernest Rutherford
scientist who conducted the gold foil experiment, shooting alpha particles at an extremely thin sheet of gold foil and discovering they were interacting with and being repulsed by small, dense, sparsely distributed points within the foil
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problems with Rutherford's model
failed to describe how electrons moved around the nucleus, unable to describe the chemical properties of electrons, no explanation of why electrons weren't attracted to the nucleus
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Democritus
thought of the "atom" is the smallest, indivisible unit of matter (first to coin the term)
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John Dalton
devised an atomic theory that said atoms were indivisible, atoms of a given element are identical, and atoms of different elements combine in constant proportions to form compounds
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J.J. Thomson
discovered the negatively charged electron using the cathode ray tube
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Robert Millikan
used the "oil drop" experiment to determine the mass of the electron
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isotope
atoms of the same element with different numbers of neutrons and different mass
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ion
atoms of the same element with positive or negative charge
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devices used to detect radiation
Geiger counter, scintillation counter, film badge
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wavelength
the distance between two crests or two troughs on a wave
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amplitude
the height of a wave from origin to crest/trough
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crest
the highest point of a wave
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trough
the lowest point of a wave
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frequency
the number of waves that pass a certain point per unit time
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types of electromagnetic radiation
radio waves, microwaves, infrared, visible light (red-violet), UV, X rays, gamma rays
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dual wave-particle behavior of light
electromagnetic radiation behaves like a wave and a particle (photon)
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atomic emission spectrum
the specific range of frequencies emitted by an atom when its electrons drop from an excited state to a ground state
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excited state
energy level occupied by an electron that has absorbed energy; further from the nucleus
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ground state
energy level occupied by an electron that has released or not absorbed energy; closer to the nucleus
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Bohr model
a model of the atom in which electrons move around a positively charged nucleus, occupying fixed energy levels
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problems with the Bohr model
electrons don't really move in circular orbits, unable to describe the chemical properties of anything other than hydrogen
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quantum
the specific amount of energy that must be absorbed or emitted by an electron for it to change energy levels
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quantum mechanical model
the current best description of the way electrons orbit the nucleus (in probability clouds; orbitals describe areas of highest probability)
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Heisenberg's uncertainty principle
it is impossible to know both the location and momentum of a particle with infinite certainty at the same time
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sublevel
a subdivision of energy levels (n): s (2 e), p (6 e), d (10 e), f (14 e)
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orbital
a region in which there is a high probability of finding an electron
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Aufbau principle
electrons occupy the lowest energy levels first and fill higher energy levels as more exist
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Pauli exclusion principle
an atomic orbital may describe, at most, two electrons with opposite spins (up/down)
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Hund's rule
one electron of a certain spin is placed in each orbital before electrons are paired up in a certain orbital