salt water or sugar water, which freeze the fastest and why?

Answer 1

If you make them the same concentration (say 1 molar of each) the salt water will have a lower freezing point, and so will need to be colder before it freezes. Freezing point is affected by the concentration of particles dissolved in the solution. Since salt forms two ions and sugar forms only single molecules, you have more particles in a salt water solution than you do in a sugar water solution.

Answer 2

sugar water because salt eats ice