Reading the article by Alex Acosta suggested me the idea of amending Standard 5.3.2. The standard suggests employing substances capable of changing its phase state upon different conditions. However, in many cases no phase state change is required. It suffices that a substance starts looking as if it transitioned to another phase state without actual transition. For a fluid, for instance, to start looking as a solid its viscosity has to increase dramatically. In other words a fluid has to become thick. If a fluid could be converted from a very thin to a very thick, then no phase transition from fluid to solid might be required to solve a problem.
Non-newtonian fluids can be converted from very thin to very thick upon application of a shear force. That is why it might appear that they change their phase state, whereas they don't.
Thus, Standard 5.3.2 has to be amended as follows:
For instance, make use of fluids that can be converted from very thin to very thick to look as if they become solids, e.g. non-newtonian fluids.
Similarly, make use of gases with controllable viscosity (or density, or some other parameter) to convert them from very thin to very thick to make them look like fluids.