Why are lubricants necessary? decrease loss of energy
reduce friction
used as fuel
increase heat energy

reduce friction

Explanation:

Lubricants are needed to reduce the friction between two bodies in contact with one another.

Frictional force is a force that opposes the motion of a body. As a body moves forward, friction acts in an opposite direction.

thats a little if u want the answer just look it up on google thats what i do haha : )

  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-