 | Term | Definition |
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Isotope |
Atoms of the same type; they have the same number of protons, but different numbers of neutrons. |
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Atom |
The smallest particle into which an element can be divided and still have the properties of that element. |
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Ion |
An atom that has gained or lost electrons; it is an atom with an electrical charge. |
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Electron |
A negatively-charged particle that is located outside the nucleus of the atom. |
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Proton |
A positively-charged particle that is located in the nucleus of the atom. |
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Nucleus |
The center of an atom, containing the protons and neutrons. |
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Electron cloud |
The region inside an atom where electrons may be found. It is outside the nucleus. |
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Energy level (shell) |
A specific area in an atom at a definite distance from the nucleus, where electrons are most likely to be found. |
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Valence electrons |
The electrons in the outermost energy level of an atom. |
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Atomic mass |
The average mass of one atom and all of its isotopes of an element. For one atom, it is the number of protons plus the number of neutrons. |
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Atomic number |
The number of protons in the nucleus of an atom. It identifies the element. |
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Electric charge |
The sum of the charges within an atom. In a neutral atom, the charge is 0. |
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Element |
A pure substance that cannot be broken down into a simpler substance. It is made of only one kind of atom. |
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Periodic table of elements |
A way of organizing elements. It is a chart where all of the elements are arranged according to their atomic number and properties. |
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Group (or family) |
A vertical column of elements on the periodic table. Elements in the same group have similar properties. |
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Period |
A horizontal row of elements on the periodic table. Elements in the same period have the same number of energy levels. |
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Metal |
Found on the left-hand side of the periodic table. An element that is shiny, ductile, malleable, and a good conductor. |
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Nonmetal |
Found on the right-hand side of the periodic table. An element that is not shiny, ductile or malleable and is not a good contuctor. |
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Metalloid |
Found along the zig-zag line on the periodic table. An element that has properties of both metals and nonmetals. |
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Physical property |
A property of a substance that can be observed without changing the identity of the matter. Examples are mass, volume, density, color. |
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Chemical property |
A property of a substance that is based on its ability to react with another substance. Examples : ability to rust, oxidize, react, or burn. |
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Symbol |
A one or two letter abbreviation for the name of an element. |
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Compound |
A combination of matter. A substance made of two or more elements that are chemically combined. |
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Molecule |
Two or more bonded atoms. They may be the same type of atom, or different types of atoms. |
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Mixture |
A combination of matter, not chemically combined; they may be separated by physical means. |
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Physical reaction (change) |
A change in matter that does not result in a new or different substance. |
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Chemical reaction (change) |
A change that takes place when two or more substances interact to form new substances. The new substnaces have different properties than the original ones. |
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Chemical formula |
A description that uses numbers and element symbols to represent the atoms and the numbers of atoms that make up a compound. |
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Chemical equation |
A way of representing reactions: the re-arrangement of atoms using chemical symbols and numbers. |
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Balanced equation |
A chemical equation in which the number of atoms of each substance are equal for both the products and the reactants. |
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Product |
What is formed from a chemical reaction. The elements and compounds to the right of the arrow. |
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Reactant |
A starting material in a chemical reaction. Elements & compounds to the left of the arrow. |
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Endothermic |
A chemical reaction that results in energy being absorbed. More energy (usually heat) is used than given out, resulting in a reduction in temperature. |
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Exothermic |
A chemical reaction that results in energy being given off. More energy (usually heat) is given out than used, resulting in an increase in temperature. |
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Law of conservation of Mass (Matter) |
States that mass is neither created nor destroyed in an ordinary chemical reaction, it only changes forms. |
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Heat |
A form of energy that is transferred by a difference in temperature. |
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Temperature |
A measure of the average kinetic energy of the particles in a sample of matter. |
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Thermal energy |
The kinetic energy of molecular motion. Measured as temperature and perceived as heat. |
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Kinetic Energy |
Energy of motion. |
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Heat transfer |
The flow of heat from one substance to another. |
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Conduction |
The movement of heat from one molecule to another in direct contact. |
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Convection |
The transfer of heat by circulation through a gas or liquid. The process in which cool fluids move down, while warmer fluids rise to the top. |
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Radiation |
Energy that is radiated or transmitted from place to place in the form of rays or waves. |
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Specific Heat |
A measurement of a material's capacity to store thermal energy. The heat required to raise the temperature of one gram of a substance one degree centigrade. |
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Heat capacity |
The ability of matter to store heat. |
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solid |
physical from of matter w/ a definite shape and volume |
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Liquid |
A state of matter that has a definate volume but not a definate shape. |
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gas |
a form of matter that takes the shape and volume of its container, meaning that it has no definite shape or volume |
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plasma |
One of the states of matter that exists at very high temperatures and the molecules have been separated into electrically charged particles. |
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