LAB REPORTS- PHYSICS AND CHEMISTRY

LAB SESSION VISCOSITY

Substance	Time (s)	Time 2 (s)	Average
Propyl acetate	0,48	0,48	0,48
Methyl acetate	0,30	0,34	0,32
Butyl acetate	0,23	0,26	0,25
Ethyl acetate	0,42	0,40	0,41

Substance	Time (s)	Time 2 (s)	Average	Molecular weight
Butanol	0,33	0,31	0,32	74,12
Propionic acid	0,27	0,18	0,23	74,08
n-Pentane	0,21	0,18	0,20	72,15
Diethylether reinst	0,18	0,11	0,15	74,12

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.

Materials:

·         Group of substances 1 (similar molecular weight): diethyl acetate, pentane, methyl acetate, butanone, butanol, propionic acid.

·         Group of substances 2 (homologous series): methyl acetate, ethyl acetate, propyl acetate, butyl acetate.

·         100 mL measuring cylinder

·         Small spheres of iron or glass

·         Chronometer

Security:

-          Use goggles

-          Diethyl ether is extremely volatile and flammable. Manipulate it always in a ventilated place and away of flames and sparks.

-          All these substances are volatile. Avoid inhalation.

Procedure

1.      Fill the measuring cylinder with 100 mL of one of the substances.

2.      Drop one of the spheres as close to the liquid surface as you can.

3.      Measure the time that the sphere takes between the 10 mL and the 80 mL mark in the tube.

4.      Repeat steps 2 and 3 twice.

5.      Return the liquid of the measuring cylinder into its container and retrieve the balls.

6.      Rinse the measuring cylinder with some acetone and let it dry.

7.      Repeat the whole procedure for the other liquids provided.

8.      Return the liquid of the measuring cylinder into its container and retrieve the balls.

9.      Rinse the measuring cylinder with some acetone and let it dry.

10.  Repeat the whole procedure for the other liquids provided.

Graph:

1. Find out what relationship exists between the drop time and the viscosity. REFERENCE!

On this part of the experiment we have on the same substance two different times because we need to do the experiment 2 times, as it is asked on the handbook, but we can see that the time it is more or less the same. Viscosity is a measure of how well substances flow. So, our conclusion would be if more time is given to a substance to get from the top part to the deep part of the test tube, more viscosity would have. And as we can see on the table, with the substances Butanol and N-Pentane; Butanol, timeà 0.33 & 0.31 and has a viscosity of 74.12. N-Pentane, timeà 0.21 & 0.18 and has a viscosity of 72.15.

Butanol has a higher viscosity because it has been required more amount of time, on the other hand, N-Pentane is the opposite.

2. Find out what relationship exists between viscosity and intermolecular forces.

If we have a substance with stronger intermolecular forces, we obtain a higher viscosity. As an example, we can see this with N-Pentane and Propionic acid, N-Pentane has one intermolecular force (Van der Waal) and Propionic acid has the three intermolecular forces, as a result we obtain that N-Pentane has a viscosity of 72,15 and Propionic acid a viscosity of 74,08. 

3. Find out what intermolecular forces have each substance.

Propyl acetateà Van der Waals and permanent dipole-dipole

Methyl acetateà Van der Waals and hydrogen bonding

Butyl acetateà Van der Waals and permanent dipole-dipole

Ethyl acetateà Van der Waals and permanent dipole-dipole

Butanolà hydrogen bond, dipole-dipole force and Van der Waals

Propionic acidà Van der Waals

N-Pentaneà Van der Waals

Diethylether reinstà Van der Waals and hydrogen bonding

4.      Explain the meaning of your results and write out your conclusion, including if possible, data from the bibliography.

In this experiment we found out what intermolecular forces had some elements, we discovered some interesting results, and our expectations were exactly the same as the results. In exercise number two, we founded out the relation between viscosity and intermolecular forces. The experiment was kind of complicated in the way that it was difficult to record the exact time because the little sphere was very fast at the time to go down the test tube. As we can see, the time-results of the first table are higher than the results on the second table. This could be because the chemicals on the second table are lighter than the chemicals on the first table.

5. Evaluate the procedure in respect to precision and accuracy of the results. Indicate weaknesses and sources of error and improvements for them.

1.      Fill the measuring cylinder with 100 mL of one of the substances: We were very precise and we used a test tube were the 100mL were marked.

2.      Drop one of the spheres as close to the liquid surface as you can: This step was very easy; we just had to drop the little sphere. Maybe we could have tried to be more precise at the time of starting to record the time.

3.      Measure the time that the sphere takes between the 10 mL and the 80 mL mark in the tube: this step was the hardest step, we had to be very precise, and sometimes, we repeated the step several times. To solve this, we might have talk to each other more to be more precise. 

4.      Repeat steps 2 and 3 twice: the same.

5.      Return the liquid of the measuring cylinder into its container and retrieve the balls: clean

6.      Rinse the measuring cylinder with some acetone and let it dry: clean

7.      Repeat the whole procedure for the other liquids provided: the other liquids were the same. We repeated the steps. The problems were the same.

8.      Return the liquid of the measuring cylinder into its container and retrieve the balls: clean

9.      Rinse the measuring cylinder with some acetone and let it dry: clean

10.  Repeat the whole procedure for the other liquids provided: repeat the process. The same problems.

Bibliography:

Rgecchemistryblog.blogspot.com.es,. (2015). Year 10 Chemistry Blog: Vapour Pressure and Intermolecular Forces. Retrieved 24 January 2015, from http://rgecchemistryblog.blogspot.com.es/2014/03/vapour-pressure-and-intermolecular.html

ChemistNATE | Lessons,. (2015). Effects of Intermolecular Forces. Retrieved 24 January 2015, from http://lessons.chemistnate.com/effects-of-intermolecular-forces.html