 A process by which one or more substances are changed into one or more different substances. Reactants  Products

NaHCO 3(s) + HCl (aq)  NaCl (aq) + H2O (l) + CO 2(g)  Yield sign (s) Solid (l) Liquid (g) Gas (aq) aqueous (dissolved in water)

 The number of each element in the reactants must equal the number or each element in the products.  Can ONLY change the coefficients, NEVER the subscripts. H 2(g) + O 2(g)  H 2 O (l) 2 H 2(g) + O 2(g)  2 H 2 O (l)

AgNO 3 + H 2 S  Ag 2 S + HNO 3 2 AgNO 3 + H 2 S  Ag 2 S + 2 HNO 3

H 2 O 2(l)  H 2 O (l) + O 2(g) 2 H 2 O 2(l)  2 H 2 O (l) + O 2(g)

 Nitrogen gas and oxygen gas react to produce dinitrogen pentoxide.  2 N 2 (g) + 5 O 2 (g)  2 N 2 O 5

 Potassium reacts with water to form potassium hydroxide and hydrogen gas.  2 K + 2 H 2 O  2 KOH + H 2(g)