Final answer:
To separate iodine crystals from common salt, sublimation is the suitable method. Iodine sublimes when heated, and the vapor can be deposited as solid crystals on a cold surface, leaving salt behind.
Step-by-step explanation:
To separate a mixture of iodine crystals and common salt, we can use the method of sublimation. This physical process relies on the fact that iodine, when heated, transforms directly from a solid to a gas without passing through the liquid state. The gaseous iodine can then be reverted back to a solid through the process of deposition when it comes in contact with a cold surface. Common salt, in contrast, does not sublime and will remain as a solid residue.
This can be carried out by heating the mixture in a container. As the iodine sublimes, it will form a distinctive purple vapor, indicative of iodine gas. Cooling the iodine vapor by placing a cold surface, like an ice-cold watch glass, above the container, will cause the vapor to deposit as solid iodine crystals on the cold surface, leaving behind the salt.