Suppose that a substance in a beaker is heated over a burner in a science lab. Which observation would most likely indicate that a chemical change has occurred in the substance? If the substance is a liquid or solid, an increase in temperature would indicate a chemical change. If the substance is a liquid, a change of some of the liquid to gaseous form would indicate a chemical change. If the substance is a solid, a change of some of the solid to liquid form would indicate a chemical change. If the substance is a liquid or solid, production of an odor would indicate a chemical change. FREE POINTS

  the   balanced   equation   for   reaction of   ca metal   with   o2 to   produce   cao   is as below

2 ca+ o2→ 2 cao2

  explanation

the reaction is   balanced     since the   number of atoms   in reactant side is   equal to   number of atoms   in   product side.   for   example   they   are 2   atom of   ca in   reactant   side   and   2   atoms of ca   in   the product side.

  the   process   is a   meet the   requirement   of   redox   reaction because :     calcium   is   oxidized   from   oxidation state 0   to 2+   while   oxygen   is reduced from   oxidation   state   0   to 2-

58750.08068 is the answer i think