Hi, staying at my boyfriend's house, which never gets fixed up, pretty old house, the tempatures are -11. I went to use the toliet, didn't flush so I check to see if the chain came off the plug. Look inside for the first time of the tank, and the water is black. The chain is still connected but the water is pretty low. So I add in more water to the tank, flush again and this time instead of going down, the blsck water goes into the toliet bowl. Does this mean that the toliet pipes are frozen and if, what should I/my boyfriend's family do??

a drain pipe should not freeze as there is no water setting in it.
can you access the pipes below to see if there is a cleanout that can be opened to see what/where the freezup is?

Black water usually means tannins are in the water. Well? If not a lot of water in the tank maybe the fill valve needs to be adjusted.

You say you took the lid off and discovered black water. Was there no black water in the bowl prior to taking the lid off? It sound like you have black crud lining the inside of the tank which is not that unusual. Algea or some other living organism has attached itself to the lining of your tank. Close the valve under the toilet and Drain the tank and clean the inside with a bleached wet cloth and the black will be gone.