ICE CREAM MAKER
An ice cream maker or ice cream freezer consists basically of a and with a vertical paddle, which sits inside an outer container containing the freezing agent (ice & salt) or an electric refrigeration unit. The paddle stirs and aerates the mixture to keep it smooth and prevent ice crystals from forming as the mixture freezes.
Ice floats because it is a latice of tetrahedrally bonded molecules that contain a lot of empty space
In 1846, Nancy Johnson invented the hand-cranked ice cream freezer. Nothing more is known about her. Her design was patented in 1848 by William G. Young.