Allotropy – the difficult phenomenon, and many people often confuse it with other similar concepts. So those whom "allotropic conditions of water" interest need to understand this phenomenon in detail.
What is allotropy
In science there is such phenomenon as allotropy – that is ability of chemical element to form several simple substances which differ only in a crystal lattice (features of a chemical bond, a form and order of coupling of atoms of substance among themselves). The allotropy does not depend on aggregate state of substance, both solid substances, and liquids or plasma can have it. The example of it, from seeming difficult, the phenomena is known to each school student: solid diamond and fragile graphite. Both represent the carbon atoms fastened among themselves with a chemical bond (C), only the crystal lattice of graphite is similar to flat scales, and here the structure of diamond represents branchy connections. For this reason the same chemical element which is in the same aggregate state has such different properties.
Why there is a confusion
If to consider water – it is complex substance. In other words, its molecules consist of several atoms, and the term "allotropic modifications" is applied only in relation to simple substances. The allotropy is often confused with the phenomenon of "polymorphism" of chemicals which arises only in those substances which are in strong aggregate state. The confusion occurred because, as that, and other term is at the same time applicable to the substances which are both simple, and firm at the same time. Iron can serve as an example – it at the room temperature is in strong aggregate state and at the same time is simple substance, that is consists only of atoms of one chemical element which are not connected in molecules.
Conclusion
The term "allotropy" can be applied only in relation to simple substances, and water is complex substance. Therefore it, being in strong aggregate state (in the form of ice), possesses just polymorphic modifications. According to the latest data fourteen different types of structure of ice, but, perhaps are revealed, will shortly open not one more. The majority of these modifications can exist only in the conditions of space, at low temperatures (it is below 110 degrees Celsius) or with a high pressure (to 700 atmospheres). From this a conclusion follows that on a question "how many allotropic states water has", it is possible to answer with the one and only word – at all.