Evaporation and Intermolecular Attractions
Data processing and presentation
Substance
Formula
cyclohexane
methanol
n-hexane
ethanol
1-propanol
1-butanol
C6H12
CH3OH
C6H14
C2H5OH
C3H7OH
C4H9OH
Molecular
weight
84
32
86
46
60
74
Type of strongest
intermolecular bond
non-polar interactions
hydrogen bond
non-polar interactions
hydrogen bond
hydrogen bond
hydrogen bond
ΔT [°C]
-17.6
-17.1
-16.2
-9.6
-5.3
-2.6
Table 1: Substances and their change of temperature due to evaporation. Substances are sorted in
decreasing order based on change of temperature.
Conclusion and Evaluation
Evaporation is an endothermic process that results in a temperature decrease.
We can conclude that evaporation is inversely proportional to strength of the
intermolecular forces. Hydrogen bonds are much more stronger than non-polar
interactions. Therefore was higher evaporation using substances, which have only
non-polar interactions between molecules. On the other hand substances, which form
hydrogen bonds, have smaller evaporation.
Mass of the molecule also influences on evaporation. From the alcohols in our
experiment, we can see the connection between mass and evaporation. Higher is the
mass of the molecule lower is evaporation.
Structure of the molecule also has affect on evaporation. Cyclohexane and nhexane have both similar molecular masses and the same strongest type of
intermolecular forces. Cyclohexane molecule has smaller surface than n-pentane
molecule. Smaller surface means that interactions between molecules are less strong.
This is why cyclohexane evaporated better than n-pentane.
Evaporation is a sensible process. Slight change in room’s temperature or
gentle wind during the experiment can significantly change the outcome of the
experiment.
Our temperature probes were very sensitive and sometimes unreliable. As a
result we sometimes got illogical results. We didn’t take enough measurements. We
should repeat each measurement several times to get valid results.
Some substances, such as cyclohexane, reacted with plastic protection cover of
the temperature probe. Some probes were totally destroyed after the experiment. Our
experiment wasn’t rational, because we have ruined so many probes. We should use
better probes. The ones who have metal protection cover.