Iron filings are attracted by a magnet. This is a physical property of iron but not of most other materials, including sand. How could you use this difference in physical properties to separate a mixture of iron filings and sand?

Explanation:

Direct a magnet towards the mixture of iron and sand. You can observe that only the iron filling attract magnet and come in contact with it. Therefore, after this process you'll be left with iron filling on the surface of the magnet whereas the sand particles are left on the dish

alchemy hadn't scientific methods of study, appeal to mysticism and fantasy, the knowledge of chemistry and physics were modest at that time.

alchemy was - but as new rules were discovered it either changed into chemistry or it became "unscientific".