S. Properties can be anything from composition to color to ductility. Without knowing an object's properties, it is impossible to characterize it. For example, looking at some common properties of metals helps to differentiate them from non-metals or metalloids.
Well, yeah, because the chemicals in the AlkaSeltzer when in water, fizes, because of the chemicals in the pallet.
The answer for the first question would be water. It is the substance that is a compound since it is made up of different elements. For the second item, i think the best answer is phosphorus and nitrogen. They are the limiting nutrients. For the last item, the correct answer is reservoirs.