We can use a combination of properties, including water solubility, density and magnetism to separate out the 5 constituents. For example, iron fillings are magnetic, sand and polystyrene do not dissolve in water (salt does) and polystyrene is lighter than water, sand is heavier.
Using this knowledge, we can separate out all the constituents. From this mixture, polystyrene balls can be skimmed off the top of water surface, since they will float on top of water (due to lower density). Once they are removed (by a spoon or spatula), we can filter out the mixture through a piece of filter paper or cloth. Sand and iron fillings will be retained on the filter (or cloth), while a solution of water and salt will filter through. Dry the mixture of sand and iron fillings and once dried, use a magnet to separate out the two (iron will be attached to the magnet). Heat the salt-water solution and collect the vapors. Once all the water has evaporated, we will end up with salt, while all the collected vapors can be condensed to obtain water back.
Thus, we will get all the 5 constituents separately.
Hope this helps.