If you did not add sugar, would the ice cream freeze faster or slower? Why?
If you try to freeze water it would take lesser time to freeze it than freezing a solution of water and salt.
The solute decreases the vapor pressure if added to the solvent and this reduces the freezing point.The molecules or ions (if there are any) also make the solution dense resulting in the decrease of the freezing point of the solution. As a result the process will take more time to reach a lower temperature.
4:1 solution starts freezing at 26-27 degrees F and pure water freezes at 0C or 32F