Lab Sesion 2

Objective: To relate a physical property to the intermolecular forces found in different chemicals.

Theoretical background: Many physical properties are related to the types and strength of intermolecular forces found in a chemical substance.

In this lab session we will look at the rate of evaporation, surface tension and viscosity.

Hypothesis: We are timing how much it takes to a little ball to go down through different chemicals. The chemicals have different intermolecular forces which can make them have different structures, which means different levels of viscosity.

Group 1 - similar molecular mass
Name	Molecular Mass	Time 1	Time 2	Time 3	Time average
Diethyl Ether	74,12	0,38	0,41	0,25	0,346666667
Pentane	72,12	0,41	0,32	0,34	0,356666667
Butanol	74,12	0,5	0,37	0,47	0,446666667
Propanoic acid	74,08	0,75	0,54	0,5	0,596666667
Group 2 - Acetates
Name	Molecular Mass	Time 1	Time 2	Time 3	Time Average
Methyl Acetate	74,08	0,69	0,69	0,55	0,643333333
Ethyl Acetate	88,11	0,59	0,75	0,59	0,643333333
Propyl Acetate	102,13	0,44	0,66	0,46	0,52
Butyl Acetate	116,16	0,37	0,5	0,41	0,426666667

Types of IMF´s and structure

Name	Structure	Type of IMF´s
Diethyl Ether		Van der Waal
Pentane		Van der Waal
Butanol		Van der Waal Dipole
Propanoic acid		Van der Waal Dipole

Name	Structure	Type of IMF´s
Methyl Acetate		Van der Waal
Ethyl Acetate		Van der Waal
Propyl Acetate		Van der Waal
Butyl Acetate		Van der Waal

Evaluation:

The first problem was that the balls of clay where very heavy to the viscosity of the components, this means that the ball goes down very quickly and we couldn´t see when it touch the bottom of the test tube, so we couldn´t measure the time. To solve this problem we made smaller balls of clay and we enveloped the balls in silver paper so the balls will occupies more space but the density is less so the ball will take more time to get down.        

Other problem is the time, we don´t know the exact moment when the ball touch the component and when it touch the bottom of the test tube so we cannot know when to start the stop watch and end it, in this way, the experiment is not completely correct because the results are approximated. The solution is to record when we drop the ball and we will know the exact moment when the ball reaches the end of the test tube, we get the time from the video.           

Finally, we would say that one important problem that slowed us in the procedure of the experiment was that there were many different components and we confused many times, we need more concentration on it and we have to be more organised to make a better experiment.

References:

Chemguide.co.uk, (2015). intermolecular bonding - van der Waals forces. [online] Available at: http://www.chemguide.co.uk/atoms/bonding/vdw.html [Accessed 25 Feb. 2015].

Science.uwaterloo.ca, (2015). Intermolecular Forces. [online] Available at: http://www.science.uwaterloo.ca/~cchieh/cact/c123/intermol.html [Accessed 25 Feb. 2015].