What happens to the matter that is sucked into a black hole?
A black hole is called a singularity and is produced when massive matter collapses in on itself under the pull of it's own gravitational attraction. If massive enough, the matter's gravitational attraction overcomes all opposing forces and the matter continues to collapse and shrink until it is a point. This point is a new black hole and is called a singularity.
When matter is drawn toward a black hole and falls past the event horizon, which divides light that can escape from light that cannot escape the singularity's gravitational pull, that matter is theorized to cease to exist in the universe of space and time. It will be annihilated as matter and remain only as its constituent subatomic particles. These particles will be stretched and compressed by the gravitational pull of the singularity (black hole) then become part of the singularity. This will add to the radius of the black hole, increasing it according to the quantity of compressed particles. (Stephen Hawking's new thoery changes black hole science by showing that matter in black holes isn't wholly separated from the universe of space and time but will eventually be radiated to energy by the black hole, which will dissipate over time, releasing the energy back to the space/time universe.)