Lab Motion in Air

TABLE: Time (s) taken by the projectile to reach the ground depending on the angle of release (º)

Angle of release (º)	Time taken to reach the ground (seconds)
	1st Trial	2nd Trial	3rd Trial	4th Trial	5th Trial	Average
10	1,45	1,52	1,44	1,62	1,59	1,52
30	1,39	1,41	1,40	1,38	1,33	1,38
50	1,28	1,31	1,28	1,19	1,21	1,25
70	1,09	1,12	1,15	1,09	1,09	1,11
90	1,03	1,06	0,94	1,02	0,96	1,00

GRAPH:

Conclusion:

As we can see in our results, there's a slight drop of time taken to reach the floor as the angle of release increases. This is caused due to the direction of the forces that take place during the movement of the projectile. Gravity is a force that pulls everything down to the core of the Earth, however, there are other forces that act in the opposite way in order to find an equilibrium between them both.  

     
As we incline the ramp, the direction of the force will also incline. Taking into account this and that gravity acts vertically downwards, the force exerted by the ramp acts in the direction against gravity will be weaker, it will start to move from vertical to diagonal. As less force is exerted against gravity, the quicker it will reach the floor.        
In addition, this diagonal force that the ramp produces will move the projectile to the side to which it is inclined.

The R2 value shown in the graph proves that our results were almost completely truthful as if it was 1, it would present the ideal tendency line.

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 (because our R2 value is not completely 0). These problems were:

-          The speed at which the stopwatch was started and stopped could have added some extra time to the results as there is a reaction time between the ball is thrown and when the stopwatch is started, and the same reaction time exists when the ball touches the floor, This problem could be solved by recording the experiment and this will make us able to notice the exact moment at which the ball reaches the floor by looking at the time interval between the screenshot of the ball left in the air on top of the ramp and when it reaches the floor. Another solution could be to drop the projectile from a higher position so that this time lost between the moment of dropping it and starting the stopwatch would be much more insignificant than if the time was 1 second, as if would correspond to a smaller ratio (if the time was 1 second, the error of time applied to the experiment will be of 0,25 seconds, which will correspond to a 25 % error percentage, however 0.25 seconds would correspond to a 5% error percentage of a 5 seconds trial).

-          The angle of the ramp, as it was hold with our hands to maintain it in the same position, could have changed slightly depending on the firmness of each of us holding the ramp. This could be easily solved by applying something on the bottom of the ramp, like a pile of books, to support the ramp throughout the experiment in the exact same position, as this support will remain completely static.

LAB REPORT SESSION 3: The elevation in the boiling point of acetone when applying benzoic acid

Objective:

To investigate the relationship between the molality and the boiling point of a solution.

Hypothesis:

We think that the more solute (benzoic acid) we add to the pure solvent (acetone), the higher its boiling point will be because when a solute is added to a liquid, the solutes blocks the solvent particles from reaching the surface, so the solvent particles will apply a lower vapour pressure than with the pure solvent. This means that, to overcome the external pressure made by the air, the solvent particles would need more heat as we add more solute to have the enough energy to escape the container they are in and start boiling. (Canning, O. 2015) Also, we can observe this in the equation of change in boiling point :

DTb = Kb ·m

The more solute you include, the higher molality the solution would have and a higher increasing change in boiling point that it would be.

Table: Relationship between the change in the boiling point and the molality of the solution.

Mass of benzoic acid in solution (g)	Molality (m)	First run - Boiling point (oC)	Second run - Boiling point (oC)	Average boiling point (ºC)	Change in boiling point compared to pure acetone (oC)
0	0	56	56,4	56,2	0,2
0,5	0,82	58,8	58	58,4	2,4
1	1,64	60,7	60,5	60,6	4,6
1,5	2,46	51,5	51,3	51,4	- 4,6
2	3,28	65,3	64,7	65	9
2,5	4,1	67,1	67,1	67,1	11,1

Graph:

Conclusion:

As we can observe clearly in our results, without taking on account the fourth result, which clearly an anomaly as it doesn’t follow the pattern like the rest of the results of an increasing straight line, the more mass applied of benzoic acid inside the solution, the higher its boiling point will be. As we explained before in the hypothesis, this is caused due to the block of the acetone particles by the acid to be able to float to the surface, so it needs to be an increase in the temperature to balance with the low pressure applied by the acetone and the higher boiling point that the benzoic acid particles have. (Canning, O. 2015). We can observe this in the equation of change in boiling point :

DTb = Kb ·m

The more solute you include, the higher molality the solution would have and a higher increasing change in boiling point that it would be.

Evaluation:

Throughout the experiment there have been some obvious problems which have caused the results, such as the fourth one when applying 1,5 g of benzoic acid, to alter completely and give results which didn’t followed what should really happen in the experiment. Some of this problems could be:

-          The difficulties of knowing when the solution starts boiling or not, as we didn’t have any parameters in which we could base on, so in each experiment the boiling point would start in a different state of the solution, and this could have increased or decreased the amount of temperature needed to apply to start seeing the first bubbles (which at first look they are impossible to distinguish). What we could do to solve this problem is record the experiment with the camera focused on the test tube and at the thermometer. After the solution start boiling completely we can go backwards in the video and take a closer look at the surface. Like this we could notice, at a slower motion, when exactly the first bubble appears and, by looking at the thermometer, at what exact temperature.

-          The benzoic acid didn’t dissolve completely in the acetone, either because the amount of steering wasn’t enough or because some of the solute laid on the bottom of the test tube, which can cause the temperature needed to boil the solution be lower as there is less solute blocking the surface of the acetone, and most of the solute is beneath, leaving the path for the acetone particles to apply a higher pressure. A solution for this could be to determine a specific time needed to steer the solution, also steering by touching the bottom of the test tube always, and like this all the experiments will have the same amount of solute dissolved and the acetone will apply the same pressure, so there will be no difference in the results of each experiment.

Bibliography:

Canning, O. (2015). Colligative properties. [online] Sciencesfp.com. Available at: http://www.sciencesfp.com/unit-3---colligative-properties.html [Accessed 21 Feb. 2015].   

University, P. (2015). Boiling Point Elevation. Chem.purdue.edu. Retrieved 20 March 2015, from http://www.chem.purdue.edu/gchelp/solutions/eboil.html

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:

-         

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

-         

      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