Value of the pieces

I was wondering something recently about the value of the pieces, suppose I promote a pawn to a queen for instance, if I lose that queen is it worth the value of a queen in determining postional strength or a pwan because that is what it was.

You are really not counting material value , you're counting material imbalance in reality (what do I have that he doesn't have?) .

With that being said, if I trade queens and later promote to a queen with that being the only queen on the board (all other material equal)  , well, heck, I'm up a queen ... end of story.

Furthermore, this material imbalance is memory-less, i.e. it does not matter if your queens were pawns 2 moves ago ... you only need to observe the material imbalance for EACH position and use it to come up with an evaluation as well as determine how to play the next move.

Well, the pieces that matter are the ones on the board, not the ones that have been captured. It depends what the situation calls for. If you are in a materially even position with Rooks on the board and you can promote/sacrifice the pawn to win one of the enemy Rooks, then you would be justified in saying you won a Rook for a pawn. On the other hand, if it's King, Knight, Pawn vs. King and Knight, you'd better be treating that pawn like a Queen or else the game is drawn.

 I guess the answer to your question is if the pawn is temporary a queen then it will be worth the value of a queen otherwise your opponent would not take it. he would do something else. you know he is going to waste a tempo take your new promoted queen because you have a piece that is worth 9.