By Rabbi Dovid Ostroff
Is one permitted to crush ice in order to produce cold water?
The gemora in Shabbos 51b says that it is prohibited to break ice in order to produce water. We find various reasons in the Rishonim as to why Chazal instituted this halacha.
Rashi says that it is prohibited because it is similar to performing a melacha, as one is ‘creating’ water.
The Sefer haT’ruma says that it is prohibited on account of nolad – a new entity.
What is the halachic difference between the two reasons?
According to Rashi one is permitted to place ice in an empty cup in the sun and benefit from the melted water. Since one is not crushing the ice one is not performing a melacha.
According to the Sefer haT’ruma it would be forbidden to do so because after all one is producing a new being. 
Another case would be placing meat with congealed gravy near a heat source. (Not hot enough to cause the gravy to reach 45º C and be liable for Bishul but warm enough to melt the gravy). According to Rashi it is permitted because one is not crushing the gravy and according to the Sefer haT’ruma it is forbidden.
Since it is a machlokes (dispute) what is the halacha?
The Rama  is stringent similar to the Sefer haT’ruma and prohibits these two cases. Therefore Sephardim who follow the Mechaber may place ice in empty cup in order to drink the melted water and Ashkenazim who follow the Rama may not.
According to the Rama, if the gravy or ice melted must it be discarded or remain unconsumed?
The Rama only rules like the Sefer haT’ruma l’chatchila,  and therefore one must avoid doing it. If it was done (b’diavad) or when this gravy is necessary one may benefit from the dissolved gravy.
Rav Shlomo Zalman Auerbach  however says that l’chatchila, if one has other water to drink one should not drink the water that remains from dissolved ice because it is something so paltry it is not called b’diavad.
According to the Rama – (Ashkenazim), may one place ice in water or cola, and if yes why?
According to all halachic opinions one may put ice into a drink. The melted ice combines with the liquid, whether it is wine, water or coke and is not distinguishable. The prohibition of nolad only occurs when the new item stands alone. When it dissolves in a mixture where the majority is the beverage it is permitted. 
May one crush the ice inside one’s drink or stir the drink to melt the ice?
It is prohibited to crush ice even according to the Mechaber. The question is whether this prohibition changes when crushing ice in a drink because the water hence formed is not distinguishable.
On the one hand we could say that since the water produced is not distinguishable it should be permitted, because the issue of nolad is waived in such circumstances, but on the other hand one is ‘creating’ water by crushing ice. The Mishna Berura  says that l’chatchila one should be stringent and not crush the ice in one’s drink.
Stirring the ice gently in one’s drink is another matter because one is not crushing and producing water, the water melts on its own accord. 
Is one permitted to defrost frozen orange juice?
During hot weather many are accustomed to placing orange juice, raspberry juice etc. into the freezer, which subsequently turns into a frozen drink. When required, it is removed from the freezer and after defrosting it is drunk. Would this be similar to melting ice, which l’chatchila must not be done, or for some reason is it different?
Rav Shlomo Zalman Auerbach ztz”l  says that it is permitted to defrost an item that has no use as a frozen solid, because even in its frozen state it is still called a liquid and hence it is not nolad. Accordingly he permits defrosting milk on Shabbos. He explains that ice serves a different function to water (and is indeed called another name) and hence its defrosting involves nolad, whereas frozen milk is still called milk and it does not serve a function in its frozen state.
We apply the same rule to defrosting many drinks that are merely frozen in order to cool them and consume when required. Therefore, when necessary one may freeze and defrost on Shabbos all drinks such as orange juice, apple juice etc.
Is one permitted to freeze water to make ice on Shabbos?
We find a machlokes as to whether making ice is called nolad being it a new entity, or it is permitted. The Rav of Tchebin, in his classical work the ãåáá îéùøéí rules that it is nolad and forbidden. Others permit it. 
The halacha is that A) one should prepare sufficient ice cubes before Shabbos. B) When very necessary, such as when guests are arriving, one may rely on the lenient opinions and prepare ice for them.
 There is a machlokes between the Rashba and the Rosh as to p’shat in the Sefer ha’Trumah. The Rashba learns that the issur is the end result and the Rosh learns that one is creating the new being. We discussed this in length in vol. IV shiur 15 of the Shabbos shiurim!
 Siman 320:8 and 318:16.
 Or the Rambam who holds that the reason is so one will not come to squeeze fruit.
 Siman 318:16 and M”B 320:35.
 Siman 318:16 and see M”B 318:107.
 SS”K 10:3.
 Siman 320:9 and M”B 35 and M”B siman 318:103.
 The Sha’ar Hatsiun in siman 318:146. See the SS”K 10:2 footnote 6.
 Kaf haChaim siman 320:60.
 SS”K 10:5 and footnote 15.
 See the SS”K 10:4 and footnote 14.