Does FDE encrypt all partitions?
You say you "enabled full disk encryption" -- what exactly do you mean by that? If you mean FileVault, it's not truly full disk encryption (as ecnepsnai said), it's full volume encryption for the startup volume, and your second partition is not encrypted. If you did something other than turning on FileVault, it'll depend on what you used.

If you used FileVault, it is possible to separately encrypt your secondary volume in Finder by right-clicking on it, and choosing "Encrypt" from the shortcut menu. This is based on the same "Mac OS Extended (Journaled, Encrypted)" volume format that FileVault uses, but rather than automatically using your login password to unlock the volume it'll need a plain password just for the volume.

You can record this volume password in your keychain so it'll be able to unlock and mount the second volume after you log in, or optionally use Keychain Access to move the volume password from your login keychain (available only after you log in) to the System keychain (accessible anytime OS X is running) so it can mount the volume even before you've logged in.

And a technical note: even with both volumes encrypted, you still don't quite have full disk encryption. There's an invisible partition named Recovery HD that holds (among other things) the booter file that asks for your account password at startup, and uses that to get access to the main volume. That must be available before the "disk" is unlocked, and therefore cannot be encrypted. There's also a (also hidden) EFI partition used for firmware updates, which also aren't encrypted.