8th Grade Study Guide

 

 

 

Chemistry

 

 

study of matter,

 

its properties and its behavior

 

 

 

formula

 

 

 

combination of symbols

that represent elements in a compound 

 

 

 

reactants

 

 

substance that enters into chemical reaction

 

ex. reactant + reactant = product

H + O —–>H O

 

 

 

 

coefficient

 

number in front of the chemical formula in an equation

tells how many moleclues or atoms of each

ex. H + O —>2H O

 

 

subscript

 

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

 

ex. H O

 

 

mixture

 

 

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

or

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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