A chemist is trying to classify an unknown substance as either a metal or nonmetal. What question should the chemist use to help classify the material? a. Is the material a good conductor or a poor conductor?
b. Does the material feel rough or smooth?
c. Does the material feel hard to the touch?
d. Will the material float in water?

A

Explanation:

A: Metals are ofthen the best conductors.

B: Metals and non-metals can be smooth or rough

C: Metals and non-metals can be hard to the touch

D: Metals and non-metals can float in water

  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-