LAB REPORT SESSION 2: EVAPORATION RATE

OBJECTIVE:

Relate the intensity of the intermolecular forces to a measurable property. Associate the intensity of the intermolecular forces to structural characteristics of the molecules.

BACKGROUND INFORMATION:
Evaporation rate is the rate at which a material will evaporate compared to the vaporization rate of a known material selected before. There are lots of factor affecting this: concentration, pressure, surface area and intermolecular forces. We have center on intermolecular forces. The stronger the intermolecular are, the harder are keeping the molecules together in the liquid state so the more energy is required. (Ilpi.com, 2010). 

Here we can see the chemicals we have used in the experiment:

HYPOTHESIS:

What will happen in this experiment is that the more intramolecular forces the substance has, the more time it would need to evaporate because it would need more heat energy to evaporate as the attractions between the molecules of the same substances are much more stronger and a lot more energy is needed to separate them and apply energy to the molecules so they could get out of the flask. In my opinion Ii think that butyl acetate would need much more energy and time because it has the same intermolecular forces than the other chemical, but butyl acetat, because it is bigger and it has much more elements in it, its Van der Waals' forces would be much more stronger, having a higher evaporation rate, and in the case of methyl acetate, because it is the smallest, would have a lower evaporation rate.

RESULTS:

*We haven't included the table because the data was given every 3 seconds, so there were 60 cells per chemical elements. For this reason, we decided to not include it.*

CONCLUSION:

As we can see in our results, there’s a significantly drop of temperature in each of the results, ones quicker than others, and this is caused because the substances, to gain the enough energy to break the intermolecular forces which join the substance and be able to evaporate, they absorb the only energy source or heat they have, the thermometer. That is why we can observe how the temperature in the thermometer falls during some time, because all the heat it had from the room temperature has been as well absorbed by the substance which it was inside.

Also, as we described in our hypothesis, knowing that the substance with the weaker intermolecular forces was methyl acetate and the one with the strongest was butyl acetate, it has been demonstrated that substances with weaker intermolecular forces need lees energy to evaporate, and we can deduce this because methyl acetate shows in its quick drop of temperature that, by applying the same temperature as the other substances, it needs much less time and energy to evaporate all the substance absorbed by the paper envelope completely (it ends evaporating when the thermometer goes back to the normal temperature) due to the weakness of its intermolecular forces which makes most of the molecules be able to separate easily and with less energy, and, at the same time, butyl acetate does not even show a quick drop, it only falls down the temperature very slowly, and this is caused due to the strength of its intermolecular forces which need much more energy to evaporate tan methyl acetate, so only some molecules are able to break free (that is why some heat is absorbed from the thermometer) with that weak amount of energy while most of them do not evaporate.

EVALUATION:

There were some problems that we observed after doing the experiment which could have affected our results in some way that they could have not resulted totally as they should have been. This problems were:

-          The paper envelope we used to absorb a sample of the substance which could evaporate quicker had different sizes each time we did a different experiment, could be bigger o smaller, and this affects the results because a higher amount of substance is absorbed if the envelope is bigger, so it could need more time than I should to evaporate completely. This can be solved easily by measuring each time the paper envelope and make all of them in all the experiments measure the same.

-          The time which the envelope is introduced inside the substance is not specified, so in each experiment the amount of substance absorbed by the paper can be more or less each time, which can cause the same problems as the size of the paper envelope. This also have an easy solution which is determine a specific amount of time which the paper envelope would be deep in, controlled by a chronometer. 

BIBLIOGRAPHY:

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            Ilpi.com, (2010). The MSDS HyperGlossary: Evaporation Rate. [online] Available at: http://www.ilpi.com/msds/ref/evaporationrate.html [Accessed 21 Jan. 2015].

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      Smith, C. (2009). Effects of Intermolecular Forces. 1st ed. [ebook] Illinois: Palatine High School. Available at: http://www.phs.d211.org/science/smithcw/Chemistry%20332/Quarter%202%20Unit%202/6%20Effects%20of%20Intermolecular%20Forces.pdf [Accessed 21 Jan. 2015].

By: Javier Ayala de Miguel

Daniel Casado Faulí

Jaime Fidalgo Molina