Question

There is difference in boiling and freezing point of distilled and impure water . Give reason.

Answer 1

Presence of impurities make the boiling or freezing point as high or low. Only pure substances have proper boiling and freezing point. From the value we can say whether impurities  are present or not can be decided. 
For ex., 
Water has boiling point of 100 0C. If the boiling point is higher or lower it may be > or < 100 0C