Why do hot drinks get cold when you blow on them?

Question

I can't see how it would be conduction, convection or radiation.

I've tested it and the drop in temperature is significant over tea not blown over.

Answer 1

It is down the the amount of energy required for a change in state from a liquid to a gas. The latent heat of vapourization is removed from the drink causing it to cool down.

Answer 2

i guess i'd say the following: the wind chill factor applies to a cup of tea too


If you've ever used a fan to cool yourself on a hot day, then you've felt the effects of a wind chill. A breeze doesn't make the temperature drop, but it can make it seem as if the temperature is cooler than it actually is.
The wind does this in two ways. First, it blows away the thin layer of warm air that normally surrounds you. Second, it draws away your heat by quickly evaporating any moisture that forms on your skin; the stronger the wind, the greater the evaporation and the colder you feel. The coldest wind chill ever recorded in Canada happened in Pelly Bay, NWT, where the wind took an already frosty -51 C down to a nose-biting -92 C!

Answer 3

It definitely is not due to radiation. The main reason why it works is because you are replacing the hot, moist air just above a cooling liquid with cooler, drier air. This has the effect of allowing more liquid to evaporate (since the air you are blowing is drier) and the temperature of the air is cooler. Whenever you have two bodies in contact the heat transfer is proportional to the temperature difference between the two bodies. Hope that clarifies.

Answer 4

You are moving cooler air over the surface of the drink, which allows the heat to escape quicker. The more you ripple the surface the quicker it will cool, since you are increasing the surface area. Much the same as if you stir it.

EDIT:
Is the thermometer at the bottom or top of the mug and what is the mug standing on? The heat may be conducting away from the bottom of the mug more quickly.

Answer 5

It's actually the standard enthalpy change of vaporization, ΔvHo, also (less correctly) known as the heat of vaporization.
It's the energy required to transform a given quantity of a substance into a gas.

In simple terms: IT TAKES HEAT TO TRANSFORM A LIQUID INTO A GAS.

What it happens: Hot liquids have a blanket of vapors on top of them, a tinny layer saturated with that gas. When you blow, you remove the vapors off the surface of the liquid creating a "dry" atmosphere, "inviting" the liquid to vaporise more. Now, like we said, it takes heat to transform a liquid into a gas. So more and more energy is consumed to allow more and more vaporisation as you blow, making the internal energy of the liquid (temperature) to drop quickly.

Answer 6

it is because of evaoation of water disolved in it. Evaporation causes cooling. Foe ex: When u fan u'r self, u feel comfortable 4 swet evaporates on blowinf and u can feel cool. This is because, when the water contents evaporate, they take the temperature [heat] from u'r body, to evaporate. Hence u feel cold. Tea cools in the same process, when u blow air to it.

Answer 7

Definitely it is conduction because more air from blow is coming in contact of hot material and taking away heat.

Answer 8

You are blowing the heat away, the same way an electric fan cools you off when it's hot.

Answer 9

Heat Transference - the air your blowing on the tea with is cooler than the tea therefore you "blow" the heat away from the tea

Answer 10

dude,

the air that is in contact with the hto liquid rises. once a current of air is blown over it replaces the heated air with cold air and the process repeats itself till the ambient temperature is the same as that of the liquid.