Group+_1+Lab+Report

In experiment 9 we measured the temperatures of certain alcohols and alkanes by using thermo-sensitive probe. At the beginning of the experiment we hypothesized that alcohols would require more heat to evaporate than alkanes. The reason being that alcohols have stronger molecular structures than alkanes because alcohols have hydrogen bonds, dipole-dipole attraction and dispersion forces between their molecules whereas alkanes only have dipole-dipole attraction and dispersion forces between their molecules. So during the experiment we discovered the following. We found out that alcohols in most cases had temperatures in the high 20s and alkanes in general had temperatures in the low 20s. We also found out that as the molecular weight of the compound increases, it requires more heat to evaporate. We found this out by subtracting the temperature of the probe, after the compounds had evaporated, from the temperature of the probe when it was still soaked in the compounds. Heavier compounds seem to require more energy to evaporate because as the molecular weight increases so do the dispersion forces between its molecules. This causes the compound to have a more stable molecular structure causing it to require more heat to evaporate. This is especially true for alcohol with a large molecular weight because they already have a very strong molecular structure due to the hydrogen bonds and combined with the increased dispersion forces the alcohols gain an even stronger molecular structure. Hence they require the most heat of all the compounds to evaporate. In conclusion our thesis about alcohols having a higher boiling point than alkanes was partially correct. In the usual case they do but molecular weight also plays an important role in evaporation. It is possible for an alcohol to have a lower boiling than an alkane, if the alkane is heavier in terms of molecular mass than the alcohol. So the amount of heat a substance needs to evaporate is dependant upon it molecular weight and the intermolecular forces between its molecules.
 * __ Evaporation and Intermolecular Attractions __**