A solid is not a solid when you change the shape and becomes different.
A piece of butter is a solid in solid.
a solid is something that takes up a fixed amount of space (takes up space e.g. a table or a chair) and has no air in it
It depends on which solids and what the properties are. If it is sulfur and iron, use a magnet. If it is the pretzels from chex mix, use your hands! or your mouth aha (:
Respectively are Calcium cabonate, Tungsten and Diamond (most probably)