At one atmospheric pressure condition, pure water start boiling at 100°C and it freezes at 0°C.
If we add some impurity in pure water, it leads to elevation in boiling point and depression in freezing point.
That means, water will boil at temperature more than hundred degrees centigrade And freeze at temperature lower than 0°C.
Hence we can say the given water is not pure and it will freeze at some temperature less than 0°C.