It is difficult to apply Archimedes principle to gasses especially those lighter than air.
Aluminium
That will depend on the application. For example, what may be a suitable insulator on a coal fired blast furnace may not be suitable as a lining in a winter jacket for children.
Iron - use a bunch of iron nails, wrapped many times with insulated copper wire, if making your own electromagnet.
Four elements are not mentioned but fossils contain organic material that means carbon compounds so carbon-13 isotope is more suitable, in case of radioactive elements that isotope is most suitable which have the half life period in millions of years.
the basic principle of crystallization is the fact that the solute should be soluble in a suitable solvent at high temperature and the excess amount of the solute is thrown out as crystals when it is cooled
No. It would inappropriate for anything that is already a liquid who's volume could be measured directly. Using displacement in this case would be an unnecessary complication.It would also be inappropriate for anything that was water soluble as displacement would not be an accurate measurement of volume.
The Air Authorities of the country the aircraft is in
Aluminium
I do think that steel is the perfect material to use.......
carbon steele
Metallic Gasket
Carbon Fibre
it is durable and the material is somewhat cost-effective.
Anything that isn't a "forbidden material" for road transport is suitable for road transport.
No as titanium is not a suitable material for blades .
Kirksite Alloy #2
En 9 material composition