Why is alcohol evaporating at such low temperature?

Question

Relating to the atomic structure of alcohol or the chemical properties of it.

Answer 1

Actually, alcohol has a fairly high boiling temperature for a compound of its mass (46 AMU). Compare

propane -42°C / 231 K
ethylamine 17°C / 290 K
acetaldehyde 26°C / 299 K
formic acid 101°C / 374 K

The difference is which forces keep the liquid from evaporating.

For propane, we have van der Waals forces only.

Ethylamine and acetaldehyde both have a polar and an unpolar end. (Dimethylether similarly has a polar centre with the two unpolar rests sticking away at an angle). What we don't have (prominently, in the case of ethyl amine) are hydrogen bonds.

Ethanol and formic acid have hydrogen bonds. Formic acid lacks the unpolar rest, so has a slightly higher boiling point than ethanol.

If you compare to water, remember that water is an extremely high boiling compound for its mass. Methane boils at 112 K, ammonia at 195 K, water at 373 K. Again, the degree of hydrogen bonds determines the boiling temperature.

Answer 2

The previous answers dance around the reason why alcohol, acetone, mineral spirits or most organic solvents evaporate at low temperatures. This chemical property and all the others are determined by one thing a step above the atomic structure: its organic molecular structure. The carbon-carbon bonds are covalent, low-energy systems that experience little bonding with other molecules. In contrast, water molecules have high-energy, electron rich O-H bonds that readily attract each other. As you can guess, if molecules can hold together stronger, then it takes more energy or higher temperatures to break them apart. That is why water has a higher evaporation temperature than most organics.

Answer 3

The main factor that determines the boiling point of an alcohol or any organic substance is the size of the molecule; the length of the carbon chain. The shortest-chain alcohol, methanol, CH3OH has the lowest boiling point, followed in order by ethanol C2H5OH, propanol C3H7OH, butanol C4H9OH, pentanol C5H11OH and so on. The reason is, the bigger the molecule, the more heat energy it takes to make nearby molecules move independently of each other.

Answer 4

Alcohol has a lower boiling point and less surface tension than water. The alcohol molecules do not "stick together" as much as water molecules do. That allows it to evaporate more easily, because it takes less energy for a heated alcohol molecule to escape from the liquid and become vapor.

Answer 5

Carbon, no carbon, it doesn't matter. The vapour pressure is all that matters. Alcohol has a lower vapour pressure then, say, water. Therefore it will evaporate faster than water. Vapour pressures can be found in most advanced chemistry books.

Answer 6

Because the boiling point is lower. The molecules are excited more at room temperature than water. Heat water, and it will evaporate just as quikly.

Answer 7

whether a perticular substance will evouprate or not is depends on the vaoupu pressure of that substance and not strictly depends on temperature if you further lower the temperature but lower the pressure of the surrounding it will still evouprates.........so the important thing is vapour pressure .........i hope this answers your question
best wishes

Answer 8

because it's flammable and therefore a source of it's own heat.