What happens when liquid changes to gas? 1.Added heat makes water molecules move fast enough to overcome the attraction
between them
2. Heat causes molecules to speed up and merge together (Which one?)

#1

The temperature that this happens is called the freezing point and is the same temperature as the melting point. As more energy is put into the system, the water heats up, the molecules begin moving faster and faster until there is finally enough energy in the system to totally overcome the attractive forces.

Explanation:

#2

Heating a liquid increases the speed of the molecules. An increase in the speed of the molecules competes with the attraction between molecules and causes molecules to move a little further apart. ... A decrease in the speed of the molecules allows the attractions between molecules to bring them a little closer together.

answer; economic order quantity;

  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-