There won't be an indicator showing that the microphone is connected. But as mentioned above, they will work. If you have a pair lying around it won't hurt to give it a try and see what issues, if any, there are from using the headphones.
When my wife upgrade from the iPhone 5 to the 5c I snagged her new pair of "Earpods" that came with her 5c since she still had the ones from her 5. They work fine. I don't use them often as I got a free pair of JAX from Motorola that match my phone and still have my old HTC One's excellent earbuds, but I have used the Earpods to make calls using their built in mic with no issues.