Chemistry Definitions

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A change in matter that makes one or more new substances

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Chemical Reaction

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a solid that forms from a chemical reaction

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Precipitate

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endothermic reaction

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A reaction that ABSORBS energy

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exothermic reaction

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A reaction by which heat energy is RELEASED.

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molecule

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A particle made up of two or more atoms

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a chemically combined substance made up of two or more elements

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compound

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an easier way to show chemical reactions by using symbols instead of numbers

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chemical equation

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formula

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A combination of symbols that equal elements in a compound

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____ show the ratio of the atoms in different elements in a compound.

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subscripts

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the substances in the beginning of a chemical equation

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reactants

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products

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the reactions of a chemical equation

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coefficient

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a number placed in front of a chemical formula in an equation

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synthesis

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when two or more substances come together to make a more complex substance.

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decomposition

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breaking down compounds into simpler products

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when one element replaces another in a compound, or when two elements in different compounds trade places

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replacement

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the minimum amount of energy needed to start a chemical reaction

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activation energy

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concentration

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the amount of one material in a given amount of another material

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the material that INCREASES the rate of a reaction by lowering the activation energy

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catalyst

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the cells in your body that contain biological catalysts

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enzymes

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inhibitor

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a material used to DECREASE the rate of a reaction

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the principle stating that matter isn't created or destroyed during a chemical reaction

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conservation of mass

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the force that holds atoms together

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chemical bond

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A substance that cannot be broken down into other substances by chemical or physical means

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element

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the center or core of an atom

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nucleus

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a property that occurs when a substance interacts with another substance.
properties: flammability

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chemical property

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the average mass of one atom in the element

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atomic mass

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____ usually give up valence electrons in a chemical reaction.
properties: hardness, shininess, etc.

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metal

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_____ have no physical properties of metals, and usually gain or share valence electrons in a chemical reaction.

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non metal

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particles that have a positive charge

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proton

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particles that have no charge

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neutron

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particles that have a negative charge

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electron

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metalloid

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elements that have some metal properties, and some non metal properties.

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period

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the horizontal rows on the Periodic Table

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group

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the elements in a collum on the Periodic Table

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symbol

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contains one or two letters, identifying the element

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Periodic Table

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A table that classifies the properties of elements

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physical property

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a property observed without changing the substance into something else.
properites: density, melting point, etc.

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electron dot diagram

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A diagram used for the number of valence electrons on an element

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valence electron

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the electron farthest away from the atom

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atomic mass unit (amu)

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measures the particles in atoms

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atomic number

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the number of protons in an elements nucleus

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atom

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the smallest particle of an element. (made up of a nucleus and electrons)