[AdiDex]

I was watching a video on Edx.org. I have some doubts. The addition of network modifiers in the glass decreases its viscosity as given in this graph (mole%.jpg attached).
Why Li₂O decreases the viscosity most? Even it's slope is also have most steepness.Why ??

After some time, Professor raised the same question and said that the most important thing is mole/cc. When we plot a graph having the same mole per cc for all alkali oxides than the effect of every alkali oxide is same. (Mole per cc.jpg Attached)

But If we assume that M₂O (M=Alkali metal) is spread out uniformly then shouldn't Mole% directly proportional to Mole per CC. Then why we have these two different graphs?