Does blowing on our hot food before we put it into our mouths actually make a difference to how hot it is?
Does blowing on our hot food before we put it into our mouths actually make a difference to how hot it is?
I'm thinking that no, it doesn't. Which begs the question of why we do it? Is it a psychological thing?
Yes, it does. By blowing over it, you evaporate some of its water, which cools it down. See also https://en.wikipedia.org/wiki/Enthalpy_of_vaporization
You can test your hypothesis of "no, it doesn't" pretty easily. Feel free to report back with results and method used.
Methods:
- Make a cup of Hot Chocolate
- Get two spoons, put them in your hot chocolate to warm up to remove the variable of heat transferring into the spoon.
- Take one spoon out, fill it up, blow on it for a few seconds, then put it in your mouth.
- Take the second one out, leave it out for the same amount of time you would have if you had blown on it, then put it in your mouth.
Report on temperature difference. If you had an instant-read thermometer you could even be more certain of the results.
Air cooled engines quite literally stay cool by being blown on.
It does. Heat conduction is faster when the temperature difference is large. Air soaks up a lot of heat, so still air is a poor heat conductor. If you're blowing it around, you're increasing the amount of fresh, colder air that can interact with the food.
One spoonful and a couple of breaths is small enough stuff to have a relatively small effect and a lot of error margin, though.
I would think it does, because you are blowing comparatively cold air on it, which will transfer some heat out of the food.
It works well enough for CPUs and graphics cards.
Convection says yes.
Yes, it does
Besides evaporation, blowing on something which is very hot will bring it closer to room (or breath) temperature by removing the air right next to it which has been heated up already and is 'protecting' the hot item a bit from direct exposure to the room air. When you blow that hot air away the hot item then touches the room air and heats that up, which cools it down.
The same applies to cold things, you can melt ice cream for example much faster by blowing on it even if you use a fan instead of hot breath.
The simple answer is that it takes time. You've removed it from the hot pile of food and given it a few moments to cool, surrounded by cooler air.
I bet if you did an experiment where you blow on on spoonful while it waits and with the next one you just pause without the blowing, you'd find little difference between the two experiences.
You know how you wind can make you feel pretty cold even when it's warm outside? The effect is even stronger for food, since the ratio of surface area to volume is bigger, and the temperature difference is much bigger.