Attending an in state college
Well a solid and a liquid is completely different from a gas. For a gas you need to have an air tight seal in order for the gas to stay in, or a special type of container so the gas doesn't decompose the container. And a liquid or a solid it's self explanatory. With some liquids you need special containers to hold the liquid so it doesn't decompose the container it's in.
A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its chemical composition and the way in which it is formed
Salt hydrates are an important class of PCMs. An inorganic salt hydrate (hydrated salt or hydrate) is an ionic compound in which the ions attract a number of water molecules, which are then trapped inside the crystal lattice. A hydrated salt has the generic formula MxNy. nH2O.
These are called resistors.