Final answer:
To cool small batches of hot food, an ice bath or ice paddles are recommended for rapid and safe temperature reduction. Ice cools metal more effectively due to its lower specific heat. For biological specimens, a combination of water and dry ice in a cooling bath is used to maintain a temperature of around 0°C.
Step-by-step explanation:
The question is asking about the best method to cool small batches of hot food. To cool small batches of hot food quickly and safely, one would use an ice bath or ice paddles. Cooling food rapidly is crucial to limit the growth of bacteria and ensure food safety. It is important not to cool food at room temperature as it allows bacteria to proliferate. Using a refrigerator is often not advisable for large batches of hot food because it can raise the internal temperature of the fridge, putting other stored foods at risk. However, for small quantities, a refrigerator may be used if the food is placed in shallow containers for faster cooling. An ice bath would rapidly bring down the temperature by maximizing the surface area that is in contact with the cold temperature, hence transferring heat away from the food more efficiently. Using shallow metal containers in a refrigerator can also aid in the cooling process, as metal tends to conduct heat away from the food better than plastic or glass.
As for the science behind the correct item selection based on thermal properties, ice would reduce the metal's temperature more in comparison to water because the specific heat of ice is less than that of water. This means that for a given amount of heat removed from the system, the temperature of the metal will decrease more when in contact with ice as compared to when in contact with the same mass of water at the same initial temperature.
A cooling bath is utilized to maintain a constant low temperature for various applications, such as preserving biological specimens like in the case of Po'lah's severed hand. To keep the cooling bath at around 0°C, Po'lah would likely use a combination of water and dry ice. While methanol has a lower freezing point than water and could be combined with dry ice, water is typically more readily available and sufficiently meets the 0°C requirement when paired with dry ice, which sublimes at -78.5°C and provides the cooling needed without going to excessively low temperatures that could cause further damage to the specimen.