Statement of Purpose (MS/MA vs PhD) Is there any fundamental difference between a statement of purpose for a masters and a PhD? 

In particular, I am talking about North American graduate schools and in the fields like mathematics and science where there is a high degree of technical knowledge. This means that there may be quite a significant difference in the level of maturity when comparing a potential master's student and a potential PhD student

For instance, it may be more understandable for a student applying for a master's to have a less extensive research experience than someone who is applying for a PhD. But on the other hand, it also seems to make sense that the committee for graduate applications would be the same and it may be difficult to actually distinguish the difference. 

My question stems from the fact that I don't seem to see any examples of statement of purposes that explicitly mentions that they are applying for a masters. 

I would be thankful for any insights.
Actually your Statement of Purpose should talk about your purpose in seeking the degree. Often the purpose of seeking a Master's is different from that of a potential doctoral application. Sometimes one seeking an MS doesn't intend to go further and apply the knowledge in industry. Sometimes the real purpose is just a stepping stone to a PhD. 

State your purpose honestly. What are your real goals. It isn't normal in North America to have a lot of research experience at the end of a BS. Whether it is at the end of an MS depends on the field and the university. A terminal MS may not include a lot of research either, as the purpose is different. But one leading to later doctoral study will probably get you started in doing research. 

Also, in North America, in many (most?) fields, you can apply directly to a doctoral program with a BS/BA. The term of study will be longer than if you already have an MS, but you can be accepted. The MS may come along more or less automatically as you progress, perhaps with a required MS Thesis. 

But in any case, the SOP should state what your goals are no matter the degree you seek. It is even acceptable at that stage to be somewhat tentative about your goals, provided that your background and work ethic is good. You don't have to decide for the rest of your life when you are only about twenty years old. 

It isn't the degree that determines what is appropriate. It is your own goals as you see them and want to work towards them.