Typically all food contains water. Some water molecules in the food are always evaporating (check this article for why). Hence, the air right on top of the food surface contains more water molecules.
The water molecules in the air right on top of the food move randomly. Some of them move towards the food, and others move away. The ones that move towards the food get back into the food. But, the others are lost. Thus, the food gradually loses some water and drys up over time.
Suppose, we cover the food with a lid, the water molecules moving away from the food eventually bounce back from the lid. Thus, placing a lid over the food avoids constant water loss otherwise. All the water lost from the food is contained in the air under the lid.
Hot food left open cools fast because the water molecules evaporating carry energy away with them. Faster moving water molecules or energetic molecules are more likely to evaporate. Thus, the water molecules that stay have less energy or smaller temperature (check this article for temperature). Arresting evaporation by placing a lid on the food slows the loss of heat. Thus, hot food in a closed container remains hot for a longer time.
Clothes dry up faster in open, wind, and dry air for the same reason. Sunshine or heat speeds up drying. Higher temperature implies more energy in the random motion of molecules. Hence, many more of them escape and evaporate.
Author: Dr. Gururaj Naik.
LinkedIn Profile: Visit here.
For more updates please subscribe to telestreak via email.
Prev : What are temperature and pressure
Next: Coming Soon
