I was playing a friend and I took her queen. She said that I didn't say "queen check" beforehand. I have never heard of this. Is it a rule?
The official FIDE laws of chess do not know about a queen check. Announcing a "queen check“ might even be considered a case of "to distract or annoy the opponent“ (11.5). Even announcing a "king check“ is not recommended.
That’s for tournament chess. In informal games, it is not unusual in some groups to announce a check and a "queen check“ (by "gardez“, French for "keep attention“). Even there it is not a rule, but a courtesy. Not announcing a check or gardez is considered impolite, but you may take the queen anyway.
Some people think it is polite to say 'gardez' to alert a player that the Q can be taken.
But no rule says you have to say check nor gardez and in serious games with good players it is not done.
This gardez for Qs is just a very informal rule amongst some low level players that I have not seen in actual use for 60 years but have read about as being more common (where?) in the past. It is possible that I never played at such a low level to encounter it; but I still believe it is rare perhaps because it is very old and now obsolete as even relative newish players do not need that alert.
The important part is that you and your friend agree on what to say and when. If you both agree that queen check (or gardez) is a nice thing to say, then go ahead and say it.
I suggest taking the time before your next game to clear this up. Also, if you play any friends of your friend then ask them too what they prefer.
That being said, if your friend want to play strangers, online, in tournaments, or whatever, then they will have to get used to people not saying it. If they try to make non-friends say gardez, they are likely to be met with a simple "no".
No, as others have said, not even (king) check needs to be announced. Queens can be traded or sacrificed. It's not possible to define precisely when the Q is under threat and needs response.
However chess softwares usually have a sound effect when king is checked. And in one blitz game, my opponent took advantage of that annoying sound!
[fen "1r3k2/p4pp1/8/8/8/P7/KPQ3P1/6q1 w - - 0 1"] 1. Qc5+! Kg8 2. Qxg1
I wished they had a Q alert.
It is just a courtesy designed to ease new players into a game with multiple rules, and your friend might have mistaken it for an actual one. Or maybe she's used to it and wanted to establish it as a common rule between the two of you. The game is supposed to be fun for everyone. Talk it out.
When I was a little kid, my parents would always say it to me when they were teaching me how to play. They still do, nowadays, but mostly as a means to tease me.
No because the whole point is to capture the King, so it's not necessary, & has never been an official rule as far as I know. If you do it with the Queen, why not with any other piece which ultimately has little to do with you winning? I was taught that you should announce a King check to give your opponent an opportunity to fix it, but I don't know if it's necessary.
Although the official rules of chess don't allow for takebacks in tournament or rated games, and expect players to notice when their queen is in danger, people who are playing for purposes of mutual enjoyment should adjust those rules when doing so would enhance that enjoyment. If a game has reached an interesting position but one of the players makes a silly move that would drop the queen, having the opponent take advantage of that would render the game up to that point essentially meaningless. If the opponent instead says "Are you sure you want to let me capture the queen?", and allows the first player to make a better move, the players may then be able to get more enjoyment out of the interesting position.
Beginners should play a mixture of "friendly" games which allow generous takebacks, and strict games with no takebacks, since the two kinds of game will impart different lessons. A novice who plays only strict games with other novices may place too much focus on encouraging and exploiting the kinds of blunders that experienced players would never make, and would thus be unable to formulate any kind of strategy that would have any hope against experienced players. Playing "friendly" games may allow players to get more experience against how to handle good moves by opponents (even if it takes the opponent a few tries to find a good move), but may fail to teach the discipline necessary to avoid blundering in rated or tournament games.