Tiny amounts get converted to cocaethylene in the liver. It's about 60x more potent than cocaine as a dopamine releaser.
Crack is made by adding baking soda and water to cocaine and cooking the whole thing, usually in a spoon. Ermingut/Getty Images Crack cocaine is an easier-to-manufacture form of freebase cocaine – the only difference between cocaine and crack is that the latter has its hydrochloride removed, increasing the melting point and making the drug smokable.
It's also probably more prone to abuse and compulsive use. But it's a awesome way to kill yourself.