8th Grade Study Guide







study of matter,


its properties and its behavior








combination of symbols

that represent elements in a compound 







substance that enters into chemical reaction


ex. reactant + reactant = product

H + O —–>H O







number in front of the chemical formula in an equation

tells how many moleclues or atoms of each

ex. H + O —>2H O





number in chemical formula that tells the number of atoms in a molecule


ex. H O






2 or more substances that are mixed

together but not chemically combined


ex, salad



chemical bond



force that holds two atoms together



Law of Conservation of Matter



matter cannot be created or destroyed in a chemical reaction




synthesis reaction



2 or more simple substances combine to form a new more complex substance


ex. hydrogen + oxygen = water



decomposition reaction



breaks down compounds into simpler products


ex. 2H O –>2H O + O



replacement reaction


one element replaces another ina compound


2 elements in different compounds trade places

ex. 2CuO +C—->2Cu + CO



endothermic reaction



absorbs energy in form of heat



exothermic reaction



releases energy in form of heat

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