applications of sublimation in points
Answers
2- In very cold places snow does not melt but sublimes directly into vapours
3- Freeze dried foods prepared by sublimation can be stored for a long time
4- In frost free refrigerators the ice on Wall of the freezer sublimes when warm air is circulated to the compartment
Answer:
Applications of sublimation:
(1) Frost-free freezers
They are the result of having a fan and air circulation inside the freezer. The sub-zero temperature combined with the air circulation that keeps the air arid, significantly accelerates the sublimation process. This keeps freezer walls and shelves free of ice, although ice-cubes will continually sublimate.
(2) Dye sublimation
Often used in color printing on a variety of substrates, including paper. A small heater is used to vaporize the solid dye material, which then solidifies upon the paper. As this type of printer allows extremely fine control of the primary color ratios it is possible to obtain a good quality picture even with relatively low printer resolution, as compared to other printer types of similar resolution. Pictures can be printed onto "transfer toner" papers containing sublimation dyes which can then be permanently heat transferred to T-shirts, hats, mugs, metals, puzzles and other surfaces to create beautiful designs.
(3) Creates freeze dried substances
Sublimation is also used to create freeze-dried substances like tea, soup or drugs in a process called lyophilization, which consists of freezing a solution or suspension and heating it very slowly under medium to high vacuum—specifically, a pressure lower than the vapor pressure of the solvent at its melting point. This can be well below the melting point of water if there are organic solvents or salts in the sample being freeze-dried. The resulting solid is usually much easier to dissolve or resuspend than one that is produced from a liquid system, and the low temperatures involved cause less damage to sensitive or reactive substances.