A question of science <polishes specs and looks serious>

[BroccoliSpears]

A bowl of roast yams is 40 degrees. In order for my daughter to eat the yams without burning her mouth I need to cool the yams to 25 degrees. The kitchen room temperature is 20 degrees. The outside air temperature on the patio is 5 degrees.

Will the yams cool from 40 to 25 degrees in a shorter time if I put them on the patio outside? Or does food cool at a steady rate, making it irrelevant whether the air surrounding them is 20 degrees or 5 degrees?

I've often wondered.

They will cool faster outside as there is a bigger temperature gradient (ie difference), so the air around them can take up more energy in the form of heat before it becomes the same energy level. Its less marked in something solid like yams as the energy has to get out to the surface (conduction) so the surface cools, energy moves towards the cooler bit from underneath, and so on, wheras in a liquid or gas it can move around (convection)and sort of stirs itself around to lose heat more effectively.
Make sense ?

they will cool marginally quicker outside

but spreading them out on a plate or cooling rack to increase surface area is a much more efficient way to cool them fast

I find putting stuff onto a cool plate, then then (after a minute) onto another cool plate is the quickest way I've found of cooling things down. But every time I see dp opening the window to cool dd's supper I wonder about the air temp thing.

Thank you CMOTDibbler for your excellent explanation. (excellent name by the way).

Never thought of using a cooling rack (duh!)