Ans: Because it will lower the freezing point.It helps to get freezing quicker
2) why do we add the cookies and other things, only after the milk has frozen slightly
Ans: Because they will stick to the milk If you put it before milk has frozen.
3) what are two factors that affect the freezing you think?
4) why do you need a bit of air in the bag?
Ans: It easy to move around.