When glass is formed, which of these takes place first? a) the sand turns to liquid. b) the molecules become hard. c) the sand is heated intensely. do) the molecules become disordered.

I would say D and if that's not it it's A

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The correct answer would be option C) The sand is heated intensely. A would be incorrect because the sand does not just turn into liquid. B would be incorrect because how would the molecules become hard. D is incorrect because this step comes after the heat.

  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-

catya your not at all which answer i've seen you do this on another question!