sends butterflies down my stomach??0----
I think you are confusing "sends chilled up my spine" with "gave me butterflies in my stomach." The butterflies thing is about feeling nervous. The chills up my spine thing is about feeling creeped out.
To express excitement, you should use your own expression rather than coming up with a common phrase. For example, this discussion of language and writing has me captivated, like a cat watching a mouse hole.
contribute to the vitality of Bates
Yes, so this is one of those situations where you have to zoom in on a word. What is vitality?
Answer that question as part of your essay. I don't mean to give the dictionary definition, though! that is usually a weak way to start an essay. Complete this task by explaining how you think of intellectual vitality in an academic community like Bates.
Then, discuss your passions and interests, and the clubs and programs aligned with them. It is great if you can honestly say you look forward to collaborating with people and mutually encouraging one another; it is great if you mention groups to which you belong, such as essayforum, where you are already involved in collaboration.