Is matter and energy ever destroyed?
No. At least, this is the current understanding. Matter and energy are really two halves of the same thing; whenever energy is put into something (say, accelerating a particle), it gets heavier, and whenever energy is released from some physical body it gets a little lighter. These effects are usually so small that they’re impossible to see until you either accelerate something A LOT (ie, very near the speed of light) or release a lot of mass (relatively speaking–part of an atom, say), like in an atomic bomb.
