19 terms

ch 7: prentice hall; Physical Science

Chemical Reactions
the elements or compounds that enter into a chemical reaction; found on left side of equation
law of conservation of mass
the law that states that mass cannot be created or destroyed in ordinary chemical and physical changes
balanced chemical equations
chemical equations must be balanced to obey the law of conservation of mass; balance using coefficients, never balance by changing subscripts
combination reaction
also called a synthesis reaction in which two or more substances combine to form a new compound; 2H2 + O2 yields 2H2O
decomposition reaction
a reaction in which a single compound breaks down to form two or more simpler substances; CO2 yields C + O2
single replacement reaction
a chemical reaction that occurs when the atoms of one element replace the atoms of another element in a compound; like always replace like; 2K + 2H2O yields H2 + KOH
double replacement
a reaction of two compounds to produce two different compounds by exchanging the componenets of the reacting compounds (AB + CD ---> AC + BD); CaCO3 + 2HCL yields CaCl2 + H2CO3
combustion reaction
a chemical reaction that occurs when a substance reacts with oxygen, releasing energy in the form of heat and light; CH4 + 2O2 yields CO2 + 2H2O
oxidation reaction
a chemical reaction in which a reactant loses one or more electrons such that the reactant becomes more positive in charge; always takes place with a reduction reaction
reduction reaction
a chemical change in which electrons are gained, either by the removal of oxygen, the addition of hydrogen, or the addition of electrons; always takes place with an oxidation reaction
chemical reactions
involves the breaking of chemical bonds in the reactants and the formation of chemical bonds in the products
exothermic reaction
a reaction that releases energy in the form of heat; condensation, deposition, and freezing are examples
endothermic reaction
A reaction that ABSORBS energy in the form of heat; melting, vaporization and sublimation are examples
reaction rate
rate at which reactants change into products over time. As concentration, pressure, temperature and surface area go up so does speed of the reaction.
reaction rate factors
temperature, surface area, concentration, stirring and catalysts
a substance that initiates or accelerates a chemical reaction without itself being affected; can be used over and over again
a state in which the forward and reverse paths of a change take place at the same time
reversible reaction
a reaction in which the conversion of reactants into products and the conversion of products into reactants can happen simultaneously (at the same time)
signs of chemical reactions
production of a gas, formation of a precipitate, change in color, release or absorption of heat