Key Vocabulary Terms & People

Chemistry
The study of the composition and properties of substances and the changes that such substances can undergo.
Scientific Method
Orderly adn systematic approach to gathering information in order to answer questions about the world.
Observation
Fact that is noticed either qualitatively or quantitatively, usually as an early part of the scientific method.
Hypothesis
Proposed, but unproved, explanation of observed facts.
Experiment
Carefully devised procedure for making observations and gathering data.
Conclusion
Judgment or opinion formed as a result of analyzing experimental 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
Fasctor that ramains consstatn during an experiment and is compared with the variable.
Metric System
Deximal system of measurement used interenationallly
Mass
Quantity of matter in an object
volume
amount of space that an object occupies
density
mass of an object divided by its volume.
Matter
anything that has mass and volume
solid
state in which matter holds a definate shape and volume.
Liquid
state in which matter does not hold a definite shape but occupies a definite volume.
Gas
state in which matter has no definite shape or volume.
Physical Property
characteristic of a substance that can be ovserved without altering the identy of a substance.
Chemical Property
Characteristics of a substance that cannot be observed without altering the identy of a substance.
Mixture
blend of two or more pure substances that are not chemically combined.
Homogeneous Mixture
Mixture made up of uniformly intermingled particleas that therefore dose not contain visibly different parts.
Heterogeneous Mixture
Mixtuer in which the particles are nto uniformly intermingled and that therefore has visibly different parts.
Atom
Smallest particle of an element that retains teh chemical identity of the element.
Atomic Theory of Matter
theory proposed by John Dalton stating that elements are composed of atoms, all atoms of a given element are identical but different from atoms of other elements, atoms are neither created nor destroyed in a chemical reaction.
Electron
negatively charged particle within 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 within the nucleus of an atom
Neutron
natural particle within the nucleus of an atom
Atomic Number
number of protons in the nucleus of an atom
Ion
a group that has a positive or negative charge because it has lost or gained electrons.
isotope
atom athat has the same number of protons as another atom, but different number of neutrons.
Mass Number
sum of the number of protons and neutrons in teh nucleus of a given atom
atomic mass
weighted average of the mass of the existing isotopes of an element.
Electromagnetic Radiation
form of energy consisting of waves made up of oscillations electric and magnetic fields at right angles to each other.
Amplitude
height of a wave measured from its orgin to its crest.
Wavelength
Distance between tow successive similar points on a wave
frequency
number of waves that pass a fiven point in a certain regions of an atom
speed of light
3.00×10^8 ms
Quantum
discrete bit of energy; smallest unit of radiant energy that can be emitted or absorbed
Photoelectric Effect
Phenomenon in which light can be used to knock electrons out of a metal
Photon
quantum of electromagnetic energy
Orbit
term used to describe the probability of finding electrons in certain regions of an atom.
sublevel
division of principle energy levels in an atom
electron configuration
distribution of electrons among the orbitals of an atom
Orbital diagram
representation of an atom in which arrows in boxes are used to show the elextron configuration of an atom.
Periodic Table
Arrangement of elembents in order of their atomic numbers so that elements with similar electron configurations are located in teh same column.
GroupFamily
Verticle column ofthe periodic table
Period
Horizontal row of elements in the periodic table.
Alkali Metal
element in group 1A
Alkali Earth Metal
elements in group 2A
Halogen
reactive, non-metal in group 7A
Noble Gas
inactive element in group 8A
Metal
Element that typically has a high melting point, is ductile, malleable, shiny, and good conductor of heat and electricity.
Non-Metal
element that has a low melting point and a dull surface, breaks easily, is a poor conductor of heat and elextricity, and tends to gain elextrons in chemical reactions.
SemimetalMetalloid
element ahtt does not have a metallic properties; found on the right side fo the periodic table
valence electron
electrons in the outermost energy level of an atom
electronegativity
property of an element that indicates how strongly an atom of that element attracts electrons in a chemical bond
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