I am employed at a university, and moonlight as a popular science writer. The gig is pretty ok, pays well enough and the pieces are interesting to research and write. I am paid a fixed price on a piece-to-piece basis, regardless of the time spent.
Lately the venue have started to write me with science questions unrelated to the pieces I am writing, but connected to other articles. Given my background, the questions are not hard, but can be answered with little research in about 10 minutes. This happens approximately once every or every second month. Normally I work approximately 10 h/month for them.
I don't mind answering the questions - in fact, I quite often answer similar questions for free, when people from the general public approach me - but I do feel a bit uneasy about it. I don't have great experience with the freelancing world, but the general idea is that they should pay me for answering, right?
Is this normal, and should I stop feeling uneasy about it? Should I require payment? If I should approach them, do you have any suggestions how to do it?