Wrapping words separately inside <p>

Wrapping words separately inside <p>

Hi there,

I have a (not too long) paragraph. In this paragraph a few words are wrapped with
  1. <span class="emphasize_m">
and
  1. <span class="emphasize_xl">

What i want to do is wrap all words in <span> which aren't wrapped already.
Then i want to switch all span opacities to 0 (zero).
I don't have an idea of how to wrap words separately...
Any help would be greattly appreciated!!

Thanks in advance,
Knal