Can a Catholic drink ice water before mass?
The short answer is no.
Canon Law allows one to be able to drink ordinary water and medicine only before receiving Holy Communion. Ice is not water neither in form or substance the same as water and as such is forbidden.
Exceptions to this rules are also included in Canon Law.
Can. 919 §1. A person who is to receive the Most Holy Eucharist is to abstain for at least one hour before holy communion from any food and drink, except for only water and medicine.
§2. A priest who celebrates the Most Holy Eucharist two or three times on the same day can take something before the second or third celebration even if there is less than one hour between them.
§3. The elderly, the infirm, and those who care for them can receive the Most Holy Eucharist even if they have eaten something within the preceding hour.
One can also to go to The Apostolic Constitution of His Holiness Pope Pius XII, Christus Dominus to get a clearer answer:
The Apostolic Constitution “Christus Dominus,” issued today by the Sovereign Pontiff Pius XII happily reigning, grants several faculties and dispensations with respect to the observance of the law of the Eucharistic fast. It also confirms, in great measure and substantially, the rules of the Code of Canon Law for the priests and the faithful able to observe that law of the Eucharistic fast. Nevertheless, the favorable first order of this Constitution, according to which natural water (that is, without the addition of any element) no longer breaks the Eucharistic fast (Const., Rule I), is extended to these also. But, with regard to the other concessions, these can be used only by priests and by the faithful who find themselves in the conditions described in the Constitution, or by those who say evening Masses or receive Holy Communion at such Masses authorized by the Ordinaries within the limits of the new faculties granted to them.
Although ice and water may be of the same substance H2O, they are not in the sense that they are of a different form of matter, one being solid and the other is liquid. The forms are different. Pope Pius said only natural water is permitted, not ice.
Ice may be of the same techniquely the substance as water. They do not share the same form or state. Thus in this sense they are not the same substance.