# Why do cold drinks cool you down and hot drink warm you up? What is actually happening when these drinks are consumed?

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Title says it all. Just curious

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What happens here is that you both (liquid and u) are trying to equilize the temperature so for example ur body temp (just throwing a random number here due to F and C) is 20 and the liquid has a temperature of 30 both will reach an equilibrium of 25, meaning the hot liquid got colder and you got warmer. Same happens with cold liquid u have a body temperature of 20 and the liquid has a temperature of 10 u both get to equilize at 15.

What happens here is that you both (liquid and u) are trying to equilize the temperature so for example ur body temp (just throwing a random number here due to F and C) is 20 and the liquid has a temperature of 30 both will reach an equilibrium of 25, meaning the hot liquid got colder and you got warmer. Same happens with cold liquid u have a body temperature of 20 and the liquid has a temperature of 10 u both get to equilize at 15.

They don’t, much, but insofar as they do it’s just a result of the fluid warming or cooling to body temperature.

Your body weighs, if you’re a typical human, about 70 kg. (Perhaps more if you’re tall or overweight, or a bit less if you’re quite small.) Your body’s heat capacity is pretty similar to that of water, in no small part thanks to the fact that your body *is* mostly water. In other words, heating your body by 1 degree C takes about as much energy as heating 70 kg of water by 1 degree C would.

Suppose you drink a full liter of ice-cold water at 0 C (that is, it’s cold enough to freeze but hasn’t yet, or just thawed from ice). Your normal body temperature is about 37 C, but let’s assume you’re overheated at about 39 C (that is, you’re hot enough to be in some physical danger). Since you outweigh (and since your heat capacity is similar, out-heat-capacity) the water by a factor of ~70, it can cool you by ~1/70th the difference, or by about a half a degree C. That’s meaningful, but you’ll still be somewhat overheated even after chugging quite a lot of ice water.

Similarly, for hypothermia at 35 C body temp and a scalding hot drink at 60 C, you’d only warm up by about a third of a degree C. And again, that’s if you chug an entire liter of quite hot drink (I’m pretty sure actually chugging that much at that temperature would burn your mouth and throat quite severely). A safer-to-chug value of 45 C would only heat you by ~0.15 degrees C.

For comparison, the typical energy production of a normal human body is around 100 watts at rest, which corresponds to the liter of cold water equalling about 25 minutes of passive heat dissipation. But if you’re that overheated, you’re not passively dissipating heat: your body is actively engaging lots of mechanisms to dissipate it faster. Sweating can add a few hundred more watts of cooling, meaning that your cold drink on a very hot day is probably only contributing 5 or 10 minutes worth. Not nothing, but not a ton…if the temperature of the drink is all we care about.

—–

The much more important effect, especially in heat – and it’s May, so I’m guessing that’s what’s on your mind – is hydration.

Water takes a *lot* of energy to evaporate. Evaporating water takes ~5 times as much energy as it does to heat water from freezing to boiling – about 2,500 kJ/kg. So if your cold drink ends up being sweat that evaporates – and in hot temperatures it absolutely will – you’ll get ~(37/70) = ~0.5 degrees worth of cooling from heating it to body temperature, but ~(**500**/70) = ~7.1 degrees worth of cooling from sweating it out. And *that* is a lot – seven degrees C of body temperature is enormous.

So the real answer, in heat dry enough for sweat to evaporate readily, is “the temperature of your water barely matters, you could drink scalding hot water and still cool down by a lot”.

They don’t, much, but insofar as they do it’s just a result of the fluid warming or cooling to body temperature.

Your body weighs, if you’re a typical human, about 70 kg. (Perhaps more if you’re tall or overweight, or a bit less if you’re quite small.) Your body’s heat capacity is pretty similar to that of water, in no small part thanks to the fact that your body *is* mostly water. In other words, heating your body by 1 degree C takes about as much energy as heating 70 kg of water by 1 degree C would.

Suppose you drink a full liter of ice-cold water at 0 C (that is, it’s cold enough to freeze but hasn’t yet, or just thawed from ice). Your normal body temperature is about 37 C, but let’s assume you’re overheated at about 39 C (that is, you’re hot enough to be in some physical danger). Since you outweigh (and since your heat capacity is similar, out-heat-capacity) the water by a factor of ~70, it can cool you by ~1/70th the difference, or by about a half a degree C. That’s meaningful, but you’ll still be somewhat overheated even after chugging quite a lot of ice water.

Similarly, for hypothermia at 35 C body temp and a scalding hot drink at 60 C, you’d only warm up by about a third of a degree C. And again, that’s if you chug an entire liter of quite hot drink (I’m pretty sure actually chugging that much at that temperature would burn your mouth and throat quite severely). A safer-to-chug value of 45 C would only heat you by ~0.15 degrees C.

For comparison, the typical energy production of a normal human body is around 100 watts at rest, which corresponds to the liter of cold water equalling about 25 minutes of passive heat dissipation. But if you’re that overheated, you’re not passively dissipating heat: your body is actively engaging lots of mechanisms to dissipate it faster. Sweating can add a few hundred more watts of cooling, meaning that your cold drink on a very hot day is probably only contributing 5 or 10 minutes worth. Not nothing, but not a ton…if the temperature of the drink is all we care about.

—–

The much more important effect, especially in heat – and it’s May, so I’m guessing that’s what’s on your mind – is hydration.

Water takes a *lot* of energy to evaporate. Evaporating water takes ~5 times as much energy as it does to heat water from freezing to boiling – about 2,500 kJ/kg. So if your cold drink ends up being sweat that evaporates – and in hot temperatures it absolutely will – you’ll get ~(37/70) = ~0.5 degrees worth of cooling from heating it to body temperature, but ~(**500**/70) = ~7.1 degrees worth of cooling from sweating it out. And *that* is a lot – seven degrees C of body temperature is enormous.

So the real answer, in heat dry enough for sweat to evaporate readily, is “the temperature of your water barely matters, you could drink scalding hot water and still cool down by a lot”.

So, everything likes to be as warm as what’s around it. So when you drink something warm or cold, your body tries to match that temperature.

Thing is, heat doesn’t come from nowhere, it has to come from something that’s already warm. So, the colder thing borrows heat from the warmer thing to catch up.

So when you drink something hot, your body takes heat from the drink, which makes the drink colder and your body warmer until their temperatures match. In the same way, when you drink something cold, the drink takes heat from your body to warm itself up, cooling your body and warming the drink.

So, everything likes to be as warm as what’s around it. So when you drink something warm or cold, your body tries to match that temperature.

Thing is, heat doesn’t come from nowhere, it has to come from something that’s already warm. So, the colder thing borrows heat from the warmer thing to catch up.

So when you drink something hot, your body takes heat from the drink, which makes the drink colder and your body warmer until their temperatures match. In the same way, when you drink something cold, the drink takes heat from your body to warm itself up, cooling your body and warming the drink.

It’s actually the opposite. The heat of a hot drink will make your body react by producing sweat. The hot drink does not have enough energy to significantly change your body temp, so the sweating will be a disproportionate response and in the end cool you down relatively quickly.

Cool drinks, your body will burn energy to warm it up in order to digest properly, this effort will warm you up in total.

Just look up “warm drinks make you feel cooler vice versa.”