If I may, interject, since I think both of you are trying to express exactly the same thing in different terminology. The Aristotelian argument would insist that the physical reality of bread and wine consists of both substance (which cannot be directly observed) and accidents (which can be directly observed). I believe you are using the term physical change to talk only about the observables. An Aristotelian would use physical change for either the change in a substance or an accident. So, according to traditional Thomistic language, transubstantiation by definition is a physical change. **However, according to your terminology, which seems to be based on modern scientific terminology, there is no change in the physical observables.
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I really hope this helps.
God bless,
Fr. Boyd, Ph.D. [physical chemistry, Princeton]