Why does methylated spirit evaporates faster than water
https://water.usgs.gov/edu/vapor-pressure.html
at around room temperature
vapor pressure methanol = about 13 k Pa
vapor pressure of water = about 2 k Pa
in other words the alcohol is trying much harder to get out.
Methylated spirit, also known as denatured alcohol, evaporates faster than water due to its lower boiling point and lower intermolecular forces. Here's why:
1. Boiling point: Methylated spirit has a lower boiling point compared to water. The boiling point of methylated spirit is around 78°C (172°F), while water boils at 100°C (212°F) at sea level. This means that even at room temperature, methylated spirit molecules have enough energy to overcome the intermolecular forces holding them together and transition from liquid to vapor. Water, on the other hand, needs to reach a higher temperature to evaporate.
2. Intermolecular forces: The intermolecular forces between molecules play a crucial role in determining the rate of evaporation. Methylated spirit contains ethanol, which has weaker intermolecular forces compared to water. Ethanol molecules have a polar group (hydroxyl group) that enables both hydrogen bonding and dipole-dipole interactions. Although these forces are stronger than London dispersion forces, they are still weaker than the hydrogen bonding between water molecules. The weaker forces of attraction in methylated spirit make it easier for the molecules to break away from the liquid surface and enter the vapor phase.
Overall, the combination of a lower boiling point and weaker intermolecular forces in methylated spirit allows it to evaporate more rapidly than water.