31) A reaction that gives off heat is exothermic.
32) A reaction that absorbs heat is endothermic.
33) Burning Mg is exothermic. 2Mg + O2 --> 2MgO
34) Coefficients are added to balance equations.
35) The small numbers in a formula are called subscripts.
36) NaNO3 is sodium nitrate.
37) CaCO3 is calcium carbonate.
38) NaNO3 contains five atoms.
39) C + O2 --> CO2. The reactants are C + O2.
40) The product is CO2.
41) The symbol --> means yield.
42) Ca(OH)2 is calcium hydroxide.
43) Formula mass is for ionic compounds.
44) In a chemical change the total number of atoms remains the same.
45) CO2 is carbon dioxide.
46) Hydrogen has a mass # of 1.
47) The mass of all substances before a reaction equals the mass of all substances after the reaction is called the law of conservation of matter.
48) 2H2O --> 2H2 + O2
49) 4Fe + 3O2 --> 2Fe2O3.
50) 2NaCl --> 2Na + Cl2.