Crack cocaine, often just called "crack," is a more dangerous form of cocaine. It is called "free base" because it has not been chemically neutralised by an acid base, and comes in the form of a rock crystal which is heated. The vapours produced by heating the rock are inhaled through a glass pipe (or "crack pipe") and produce feelings of euphoria and excitement. Crack is also referred to as freebase, black rock and yay. The term "crack" comes from the crackling sound made by the rocks when they are heated up. The high from crack lasts a shorter time than cocaine and tolerances cause people to need to use the drug more often and in higher doses to get the same effect and reduce the "crash" which occurs after the effects wear off. Unlike regular cocaine, which is more of a "party drug," crack is often also taken by solitary people who are using it to escape from feelings of depression or isolation. It is very dangerous and leads to hallucinations, strokes, and cardiac arrest. The need to increase dosages due to tolerance also means overdosing is very common.