On a day when I am in hurry to go to office, I have a fixed quantity of rice which was just cooked and kept in a bowl. In order to cool it quickly, which one of the following is the best option?

To cool cooked rice quickly, maximizing the rate of heat transfer is essential. Heat transfer occurs through conduction, convection, and radiation [4]. Placing the bowl in water at room temperature utilizes conduction and convection; water has a much higher thermal conductivity and heat capacity than air, allowing it to absorb heat from the bowl more efficiently than air alone [2]. Simultaneously, operating a fan at full speed enhances forced convection and evaporative cooling [2]. The moving air rapidly removes the warm, moist air layer above the rice, significantly increasing the cooling rate compared to still air or slow-moving air in an AC environment. While an AC room (Option 2) provides a lower ambient temperature, the high thermal mass of a water bath combined with high-velocity airflow (Option 3) provides a more effective heat sink for rapid cooling.

Sources

1. [4] https://www.baycountymi.gov/docs/commoditycodes.pdf
2. [1] Science-Class VII . NCERT(Revised ed 2025) > Chapter 7: Heat Transfer in Nature > 7.2.1 Land and Sea Breeze > p. 95
3. [2] Science-Class VII . NCERT(Revised ed 2025) > Chapter 7: Heat Transfer in Nature > Activity 7.3: Let us fi nd out > p. 94