My iPhone 5 sounds like the battery is loose?

I have a iPhone 5 that I bought from someone, it was new in the box. I just now noticed when I move it around and shake it, there's a noise that moves around. I'm guessing it is the battery loose. I checked the IMEI of the iPhone, and it says it still has a 1 year warranty lasting till October 1, 2013. Since I'm not the original buyer of the phone, can I still bring it to an Apple store and exchange it for a new one?

Because I've read the warranty stays with the phone, not the owners, if that's correct.

And if they do replace it for me, will they give me a new iPhone 5 in same color? Or a used one?

Added (1). So should I just bring it to an Apple Store? I called an Apple representative, and he said that it's normal and it's just the camera focus or something…

But I'm afraid that might not be the case…

That's correct.

If you read around on the internet, there's an issue with the battery adhesive in the iPhone 5. They will probably just replace the adhesive for you, not the whole phone. I have never heard of them charging anybody for it. My girlfriend and I were just talking about this - she works at an apple store.