4. what two sets of units can be used to describe density? why are they interchangeable? a. b. c.

The density of a material is its unique property. Although the density can be expressed in different scale the density of the same material remains same. The reasons for the inter-changeability of the density are-

a. The density of a material is its unique property.

b. The density usually expressed in terms of CGS or SI unit. In CGS unit it is g/mL and in SI unit it is Kg/L.

c. In both the case if we multiply 1000 to gm it becomes kilogram (Kg) and 1000 unit of mL is liter (L). Thus the value remains same.

  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-