Vescosity Test

Aim

To determine which of these: diethyl ether, Propionic acid, 1-butanol, and 1-hexanol are most viscous through an evaporation method.

Hypothesis

Propionic acid is going to be the most vicious because the stronger the intermolecular forces the more viscous. Its molecular formula is C3H602, the C is bonded to an OH and the C is also double bonded to an O. Therefore, there are strong intermolecular forces, like hydrogen bonds. Also the double bonded oxygen has a lone pair attracting the electropositive H creating a dipole moment.

Selecting Variables

The independent variable is the chemical and the dependant variable is the change in mass (g). The controlled variables are the volume (ml), the same door height of the fume cupboard, the time (s) interval and to the fix problems with density we are going to take the percentage of change in mass.

Planning (b)

Method

1. Use a Pertri dish (to support the filter paper)

2. Tare the scales

3. Find and record the mass of the filter paper.

4. Drop the chemical onto the filter paper. 1 ml of chemical

5. Record the mass of the filter paper at 10s and once at 25s

6. Subtract the mass of the filter paper from the mass recorded in the different times.

7. Find out the change in mass.

8. Calculate the difference in percentage.

9. Repeat steps 1 to 8 for all the chemicals: Diethyl Ether, propionic acid, 1-butanol, 1- hexanol.

10. Repeat the experiment if necessary

Therefore the more mass the chemical loses the less vicious it is.

Materials required

1. Scales

2. Stopwatch

3. Pipette (1ml)

4. Filter paper

5. Pertri dishes

6. Fume cupboard

We are going to keeps the volume the same by using a pipette to get 1 ml of the chemical. The height of the fume cupboard door is going to be in the same place as we used a tape to mark the place where the door was for the first experiment and incase it was moved it could be readjusted to that same position. The time interval is going to be of 15s: one experiment when the mass is recorded at the first 5s and then at 20s. The other is experiment is when the mass is recorded in the first 10s and then after 25 s. then take the result which seem to be more reasonable. The some chemical are denser than others and to control that problem we take the percentage of the mass lost.

This table shows the difference in the mass after the filter paper has been subtracted and the percentage lost has been calculated.

Conclusion and Evaluation

Form the data I have collected and processed I can see that in 15s diethyl ether lost the most amount of mass, losing 28% of the original mass meaning that it evapourated the quickest compared to the other chemicals we had. Therefore we can say that the intermolecular forces in Diethyl Ether are the weakest. Next was 1-Butanol which lost 6% of its original mass and 1-hexanol was the third losing 2% of its original mass. Lastly Propionic acid lost 0% of its original mass. Therefore, the intermolecular forces are the strongest compared to the other samples, including Van Der Waals forces, Propionic acid has 2 hydrogen bond, which makes the forces between the molecules strongest compared to the other chemicals.I conclude that propinoic acid is the most viscous out of: diethyl ether, 1-Butanol,1-hexanol and propinoic acid.

Viscosity (cP)

Diethyl Ether

0.224 at 25 C

1-Butanol

3 at 25C

Propinoic Acid

10,000

1-Hexanol

The table above shows the literature value for three of the chemicals. And from this we can see that Propionic acid is the most vicious.

There were few errors, while doing the experiment, one was the scales. It would not read a same number for more than 3s so we had to take the modal average for the masses. Also we used a stop watch and we might have noted the mass too early or too late. The pipette was a nuisance to use it was a pipette which measure 1 ml and it was hard to get exactly 1 ml but we managed. To improve this experiment we should use more of the chemical so that the time difference could be longer and we would get a better result for the change in mass. This method can determine which chemical is the most viscous but it cannot give us an exact number telling us which chemical is most viscous.