Use of modal 'would' in request or in conditional sentences

Hi,

I sometimes have difficulty in knowing if a sentence that has the modal 'would' is indicating a request or is conditional in nature.

Would you pass me the napkin? -- a polite request, it seems.
I would pass the napkin to you. -- conditional in nature, it seems.

QI need a napkin to wipe off something on my mouth. Can you pass me the napkin.

Possible As:
Yes, I can pass the napkin to you. -- the mostly likely response to get for this, I think.
Yes, I could pass the napkin to you.-- a little awkward but OK (more polite than the first one??) but has a sense of conditional to it too, in my opinion.
Yes, I would pass the napkin to you. -- carries a sense of conditional, in my opinion. How can I figure out what possibly is an ellipted (implied??) if- clause??