Does blowing on hot food really make it cool faster, and if so, why?

Depends on the density of the food. A piece of steamed cabbage held aloft with a fork, yes. A 4 inch deep bowl of boiling Oatmeal, no. lol
Stirring AND blowing would be most effective. haha

But it is not considered good manners to blow on food in a group setting.

Because of the laws of thermodynamics, the hot food tries to reach temperature equilibrium with the the air next to it. As the air becomes “saturated” with heat, the transfer slows down. Blowing on surface of the food replaces the hot air with cooler air and speeds up the transfer.

Convective and evaporative cooling. Even though your breath is warmer than room air, it’s cooler than the food, plus it entrains surrounding room air which is even cooler and drier, via the Venturi principle. So the layer of warm air adjacent to the hot food is replaced by air at a lower temperature (convective cooling) and containing lower humidity (improving evaporative cooling).

It’s more effective to blow on just a forkful or spoonful of food prior to entering the mouth than it is to try to cool the entire mass of hot food on the plate or in the bowl.

@marinelife Haha…caveat! Okay, that does change everything. No blowing in mixed company. lol

@Coloma that depends on how well you know your company, doesn’t it?

But blowing does help cool food faster.

@WestRiverrat Yes, well..I guess intimacy between friends and family can be gauged by how comfortable everyone is blowing, double dipping and slurping their soup huh? lol

Yes.

Be extra careful with high fat foods and very sugary foods, they hold onto the heat and get very hot.

Convection.