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Evaporation and Intermolecular Attractions

Rebecca Gotthelf Madeline Chiapperino 2/7/17 Chem 111L-14

Purpose: In this experiment the temperature changeds caused by the evaporation of several liquids was investigated. These results, in conjunction with the intermolecular forces known to be present, were used to predict, and then measure, the temperature change for several other liquids.

Procedure: Can be found on pages 19-21 in, “CHE 111L Lab Manual, Spring 2017”.

Data Table: Can be found at the back of the lab.

Calculations:

∆T = (T1-T2)

ethanol: T1 = 21.97°C T2 = 11.78°C T1 – T2 = 10.19°C

1-propanol: T1 = 21.86°C

T2 = 14.83°C T1 – T2 = 7.03°C

1-butanol: T1 = 22.02°C T2 = 18.37°C T1 – T2 = 3.700 °C

n-pentane: T1 = 21.79°C T2 = 1.784°C T1 – T2 = 20.01°C

Methanol: T1 = 22.41°C T2 = 2.628 °C T1 – T2 = 19.78 °C

Acetone: T1 = 22.21 °C

T2 = 5.229 °C T1 – T2 = 16.98 °C

n-hexane: T1 = 22.05 °C T2 = 9.183 °C T1 – T2 = 12.87 °C

2-butanone (methyl ethyl ketone): T1 = 22.14 °C T2 = 9.596 °C T1 – T2 = 12.54 °C

Summary of Results: Substance ∆T (T1-T2) ethanol 10.19°C 1-propanol 7.03 °C 1-butanol 3.700 °C

Predicted Bigger ∆T in comparison to propanol

n-pentane

20.01 °C

Bigger ∆T in comparison to butanol

Methanol

19.78 °C

Smaller ∆T than ethanol

Acetone

16.98 °C

Smaller ∆T than propanol

n-hexane

12.87 °C

Bigger ∆T than

explanation Bigger because the mass of the molecule is larger, so the bonds are further away from each other and can be broken more easily Bigger ∆T because it doesn’t have dipole-dipole or H-bonds so it can evaporate easier and quicker than butanol Smaller because the molecular weight is smaller than ethanol so all of the bonds are closer together and harder to break Smaller because the molecular weight is smaller than propanol so all of the bonds are closer together and harder to break Bigger because the molecular

pentane

2-butanone (methyl ethyl ketone)

12.54 °C

Bigger ∆T than acetone and butanol and smaller than pentane

weight is bigger than pentane so the bonds are farther apart, making them easier to break Bigger than acetone because it’s heavier so the bonds are farther apart and easier to break. Bigger than butanol because it has less IMFs, so there are less bonds to break. Smaller than pentane because it has more IMFs so it would take longer to evaporate.

Conclusion: The purpose of this experiment, which was to investigate the temperature changes caused by the evaporation of several liquids, and predict and measure the temperature change for several other liquids, based on knowledge of intermolecular forces, was achieved. Ethanol and 1-propanol were initially observed, and the ∆T for each respectively was, 10.19°C and 7.03 °C. The next six liquids, 1-butanol, n-pentane, methanol, acetone, n-hexane, and 2-butanone, had a ∆T value of, 3.700 °C, 20.01 °C, 19.78 °C, 16.98 °C, 12.87 °C, and 12.54°C. In this experiment, predictions had to be made based off of the first two collected liquids, ethanol and 1-propanol, based off of previous knowledge of intermolecular forces. Examples of predictions are, “a bigger ∆T than (blank) because this has a larger molecular weight, so the bonds are further away from each other, and therefore can be broken more easily”, or “smaller ∆T than (blank) because it has more intermolecular forces so it would take longer to evaporate”.

Predictions were made for six different liquids, however only one of them was right, even though the theory behind the predictions were correct. Some possible sources of error that would lead to this discrepancy could be, not properly cleaning off the temperature probe, therefore leading to multiple different liquids being measured at once. The paper that had the liquid on it, was not close enough to the probe, leading to an incorrect reading, or tape on the paper caused the reading to be inaccurate. No data was discarded in this lab....