I'd like to add a card called Chaos Burst to my burn deck.

Here is the effect of it:

Activate only by Tributing 1 monster when your opponent's monster declares an attack. Destroy the attacking monster. Then inflict 1000 damage to your opponent.

If I were to use a face down card with a flip effect as the tribute, would the effect of the flip effect monster still be activated even though it's being tributed?

If so, why? If not, why?

Such questions belong in the Rules of Dueling. Also, if you have multiple questions, just put them together in 1 post instead of making a separate thread for each one. This prevents spam.

As for the question, no it will not activate. Simply because it should be obvious. It's a FLIP: Effect. FLIP: Effects require themselves to be flipped face-up somehow in order to activate. If you Tribute it while it's face-down, it was never flipped face-up, thus it never activates. And no, you cannot flip it and then activate Chaos Burst as you can only Flip Summon during your turn, during your Main Phase 1 or 2, and by the time it is flipped by the attack, the window of timing to activate Chaos Burst has passed (the opponent declaring the attack).