Is it mutar on Shabbos to use a can of whip cream? It is liquid inside, and comes out as cream. the nozzle also giving it a shape.
The whip cream should not be used (by those who follow the rulings of Rema) on Shabbos. The pressure upon exit from the can causes the liquid to change state, and this is considered molid–causing a change of state. Moreover, it would be considered “molid beyadayim,” meaning causing a change of state (from liquid to solid) by means of a direct action, which (according to Rema) is prohibited.
See Mishnah Berurah 318:102-103; the fact that the cream reverts to a liquid state after a number of minutes does not permit the formation of the cream, as we see from the case of heating congealed sauce, which is considered molid even though the sauce will return to its congealed state after it cools.