Why is alcohol colder than water?

Question

Also, why does alcohol dry faster than water? I searched on Google and Ask, to no avail TT_TT

Answer 1

Alcohol doesn't have the chemical bond that water has so therefore less surface tension so it evaporates (dries) much more quickly. When it evaporates it cools your skin so it feel cold to the touch.

Answer 2

OK ... my answer might be long but it will help explaining this phenomena.

What Do You Think?
Which liquid is more efficient (alcohol, acetone, or water) at cooling down an object as a result of evaporation? Is there a relationship between the rate of evaporation and the cooling effect that a liquid exhibits? Is there a relationship between the boiling point of these liquids and their rate of evaporation?


Background
Have you ever heard of a person that has a high fever getting a “sponge” bath? A common home remedy for bringing down a fever is to use a sponge to apply either water or rubbing alcohol to the skin of the person with the fever. The water or alcohol is normally at room temperature to start. The method takes advantage of basic physical science theory: evaporation follows from the distribution of molecular speeds in a liquid. The faster molecules have enough energy to escape through the liquid surface tension despite the attractive forces of the other molecules. The molecules left behind redistribute the available energy in collisions among themselves. Since the most energetic molecules have escaped, the average energy of the system is less than before and the liquid is now at a lower temperature. In the case of the sick patient this has the effect of reducing the temperature of the body.
You may have already observed this cooling as a result of evaporation in everyday experiences. Here are some examples:
• Rubbing alcohol feels “cold” to the touch even if it is at room temperature. Rubbing alcohol is often used to “sponge bath” a patient who is suffering from a high fever.
• Acetone, the main component of many fingernail polish removers, also feels “cold” to the touch, even when it is at room temperature. (* Acetone is a toxic substance and should not be placed on the skin and it should only be used in a chemical fume hood)
• Your body uses water (a coating of sweat on your skin) to cool down the body when it is overheating.


Best Regards,

Answer 3

Why does it dry faster? I'm assuming you mean evaporate faster. Alcohol is much more volatile than water. Volatility is a property all liquids (and some solids such as dry ice) have, the more volatile, the faster a liquid will evaporate at standard temperature and pressure.
As for why it's colder? Well I have no clue what you mean, 10 degree alcohol is the same temperature as 10 degree water. However, alcohol has a lower specific heat capacity than water, which means it needs less energy to go up a degree of temperature, maybe that's what you meant.
Look up specific heat capacity or volatility for more information.

Answer 4

The liquid is not colder than water at a given temperature.
If you held water and alcohol in two separate containers at 72 degrees F, each liquid would eventually measure 72 degrees. NOW, if you put water on the top of your hand, if will feel cooler to you as it evaporates and absorbs body heat to do so. If you ut the same amout of alcohol on your hand, it feels much cooler by evaporating faster and absorbing more heat from your hand. It is not colder, it just sucks more heat from you faster.

It is a similar reason that it dries faster, the heat is absorbed faster and it evaporates at a lower temperature. Isopropal Alcohol evalopates at 88 deg C; water at 100 deg C

Answer 5

By colder, I assume you mean when you put it on your skin it feels colder. The answer to both your questions is the same, alcohol has a lower evaporation point than water.

Water boils at 100 degrees celsius
Alcohol boils at 78 degrees celsisus

At room tempurature Alcohol also evaporates faster than water because there are weaker molecular bonds between the alcohol molecules than there are between water molecules.

Because the alcohol evaporates faster than water it cools your skin faster than water through evaporative cooling. Here is a wikipedia article explaining evaporative coolling:

http://en.wikipedia.org/wiki/Evaporative_cooling

Hope this helps.

Answer 6

I think it is all down to science... the density of water and the components of which it is made of... ie, h20 for water which might be more bonding then what ever alcohol consists of in the periodic table or something like that.. :)

if you take gasoline, it is also cold, and evaporates quickly, it is also higly flamable, just like alcohol... so must be something to do with the components and how it is put together.. perhaps not as bonding and easily broken up when in contact with air... air can also only contain only a limited number of molecules (of evaporated particles) in an enclosed container... so, as soon as the container is open, more air could escape and evaporate :)

ok, anyway, go have a look here.. I just searched google (to see if I could validate my bs'ing :), and found this.. pretty close, i think :) lol

http://www.newton.dep.anl.gov/askasci/chem99/chem99632.htm

Answer 7

Alcohol evaporates faster than water for more than one reason. The vapor pressure of alcohol is higher, and therefore it wants to exert its partial pressure on its surroundings. Secondly, the latent heat of vaporization is MUCH lower. Latent heat is the amount of heat reuired to vaporize a substance without changing its temperature. Water has a tremendous latent heat 980 BTU/lb, which is why steam is such a good, cheap source of heat for industries. If memory serves me right, ethanol's latent heat is roughly 40-50 BTU/lb so it takes much less heat from the environment to vaporize a pound of ethanol than a pound of water. By the way, it feels cold to you because if you are in contact with the vaporizing liquid, then YOU are the heat source and therefore YOu are getting colder. The heat flows from you into the liquid. Conversely, if the vapor condenses on you, you would get hot... try holding your hand over a whistling steam teapot. Much quicker burn than if its not boiling eh?

Answer 8

Alcohol is not colder than water, alcohol evaporates at lower temperatures than water because its heat of vapourisation is less. That is also the reason, it 'dries' (evaporates) faster.

Answer 9

Most light alcohols have a weaker intermolecular force of attraction. Therefore, they tend to evaporate much easier than water.

Evaporation is a physical process which takes heat energy from its liquid origin, making the site the evaporating molecules just left, cooler.

Answer 10

It only feels colder due to it being more volatile and vaporises faster than water. Dip one finger in alcohol and one in water which are at the same temperature and blow gently on them..the alcohol will feel cooler due to its evaporation removing heat from the finger faster than the finger with water.