Final answer:
To separate water, sand, salt, and iron filings, utilize the magnetism of iron to remove the filings, filter the remaining mixture to separate the sand, and evaporate the water to recover the salt. This demonstrates a physical change where each substance keeps its original properties.
Step-by-step explanation:
To separate a mixture of water, sand, salt, and iron filings, one can follow a series of separation techniques based on the physical properties of each component. The property of iron that can be used to separate it from the mixture is its magnetism. Iron filings can be attracted and separated from the mixture using a magnet. Next, the mixture of water, sand, and salt can be addressed by pouring it through a filter, which will separate the sand from the solution of salt in water, due to the different particle sizes. The sand will remain as a residue on the filter paper, while the saltwater will pass through as a filtrate.
To obtain pure water and salt from the saltwater solution, the process of evaporation can be used. By heating the solution, the water will evaporate, leaving dry salt crystals behind. This change is physical, and the substances involved (water and salt) keep their physical properties throughout this process. The resulting components—sand, dry salt, and iron filings—are now successfully separated from the original mixture, each retaining its individual properties.