MOTION IN AIR

RESULTS - TABLE AND GRAPH

TABLE 1:  Results from the relation between the changes in the diameter and how it affects the time it takes to reach the floor. 

For calculating the area we used the main formula of the circle which is π r² (Aaamath.com, 2015) 

GRAPH 1:

TABLE 2: Results from the relation between the changing the shape of plasticine and diameter and how this factor affects its acceleration.

We calculated the acceleration with its formula A= 2s/ t2 

A= acceleration (m/s2)
S= distance (m) (1.74m)
T= time (s)

GRAPH 2:

Conclusion:

As shown in the first table we can see the relation between surface area and time. After collecting all the results in this table, we conclude that what we stated in our hypothesis was true. When we have a bigger surface area, we can see that it takes more time to reach the floor. For example, when the surface area is 28,26 cm2, the average in milliseconds it takes to reach the floor is 48,7 (1/100s). If we compare it to a plasticine flat ball with a diameter of 153,58cm2, is shown above that it took 65,3 milliseconds. Gradually, the time changes due to the surface area of every different plasticine ball. This is because of air resistance, the main factor that affects the flight of our object in this experiment. Depending on the size and shape of the plasticine ball, the time decrease or increase, as well as acceleration. Finally, after collecting the results and thinking about it, we conclude by looking the Graph 1 and table 1 that as bigger the surface area of the plasticine ball is, the more time it takes to touch the floor and this is because of the air resistance force trying to push the object in the opposite direction that gravity does. If we have a plasticine ball with a bigger surface area, the more particles and more air resitance can push up and acts on it so, this is why changing the shape and surface area of plasticine balls affects then in time and acceleration.

After doing this table, we did a graph to compare the time (1/100s) the ball takes to touch the floor in the y axes and the changes in the diameter(cm) of the plasticine ball in x axes. Its important to say that the weight of the plasticine ball is constant, keeps always the same. As we can observe in the graph the relation we obtain after comparing these two elements or factors is directly proportional. As more diameter the ball has, the more it takes to touch the floor. 

Afterwards, we decide to make a second table. In the first one the unit of time was in 1/100s because being the unit in which the stopwatch measures because the time that the balls reach to touch the floor was too short. We decide to make this second table and pass this units to second. Also, to calculate using one of the formulas from our background and calculating another different unit, we decided to calculate acceleration by this formula:  A= 2s/ t²

As is shown in the table, the bigger the surface area of the ball is, the more time it takes to reach the floor because it has less acceleration. 

To prove this relationship we did a graph (graph 2) which relates the acceleration (m/s) in y axes and the changes in the diameter (cm) of the plasticine balls. As we can see the relation between these two concepts is inversely because as the x axes increase, y axes decrease. After making the graph we get to the conclusion that what we´ve stated before, was proven and definitely correct. 

Evaluation: 

While carrying out the experiment we noticed some problems which were affected by the fulfillment of the experiment. On one hand, the plasticine shape diameter changed once it impacted with the floor. This made the diameter of the shape change. Maybe it didn't gave the exact result for that given diameter, so we had to repeat that exact part twice.

On the other hand, once the shape hit the floor, some parts of the shape stuck on the floor, making the plasticine reduce its mass. Even though its weight didn't alter the time to reach the floor, at first, we stated that the mass was going to stay constant in every try and in every trial so therefore, we had to add more plasticine and weigh it again and again in order to have the stated mass and get on with the next trial.

Once finished the experiment we thought about some points we should change in our experiment in order to avoid these problems that made us take more time to realize the whole experiment. For example:

- Searching for another object with similar characteristics to plasticine, regarding the shape, weight, its facility to change its form... This will make it easier for us, saving time.

- Another alternative we should try is realizing the experiment in a space where the impact surface it's more smooth and soft. This won't create as much variations in the shape of the plasticine as realizing the experiment in a hard surface as we did. Our solution to this problem is foam.

- Another problem is the human reaction using the stopwatch. Probably it takes about 0,25 seconds, and some of our results are about 0,5 seconds. This means that using the stopwatch could cause a 50% error in our results. In order to improve this, we could use a camera or a sensor because with it, it will be more precise and the error percentage would decrease.

- As we can see in the results, we have two different tables in which time is measured in a different unit. This is due to the fact that while performing the experiment, the time it took the plasticine to reach the floor was very quick, so the stopwatch measured the time in the unit of milliseconds, so therefore, to show this as a clearer way, we created a second table in which we measured time in the unit of seconds. Also, in this second table, we calculated acceleration with its formula in this table to have more variation in order to explain it lately in our conclusion 

Generally, we worked well as a group without important problems that could affect the whole project. We didn´t have any arguments or discussions at the beginning about the decision of which project of the two we were going to work on it. It was a really good project in which we´ve learned lots of factors as the ones which affect the flight of an object. The best thing about these projects is that, first of all we need to do an investigation in which we investigated on the internet about the topic. Afterwards, the objective is to prove that what we´ve said in the background and hypothesis have sense and is correct. Finally, after doing the action part of the project we conclude and the results and graph helped us to demonstrate that what we were saying at the beginning was correct. This method of learning is exceptional as a really good resource of learning and applying our knowledge to a theme related to this subject.

BIBLIOGRAPHY

Aaamath.com,. (2015). Surface Area of a Cylinder. Retrieved 15 June 2015, from http://www.aaamath.com/exp79x10.htm

FREEZING POINT DEPRESSION LAB REPORT

Introduction:

Freezing point depression occurs when the freezing point of a liquid is lowered by adding another compound on it. The freezing point of water is 0º, but it can be depressed by adding a solvent such as salt in our experiment. It's a colligative property of matter.

In our experiment we're going to add some sugar to 5 different test tubes (0,5/1/1,5/2/2,5 grams per test tube) and we will put them up in a salt ice mixtured beaker.

The equation that we will use later on to calculate the change in freezing point is:

Change in boiling point = Kc  x   molality 

(AT: change in boiling point)
(Kc: Cryoscopic constant, Kc for water is 1,86 and for Acetic acid is 3.9)
(molality: Mol/kg)

The more solute added in H2O, lower freezing point it will have. So, what happens when we place the test tubes in a salt ice mixture beaker?

Adding salt to the beaker with ice causes a temperature drop that slows the melting rate and increases the freezing one. The final result is that the ice melts slowly after the addition of salt. Another point to take into consideration is that as more solute, more molality, and as more molality, the freezing point gets lowered. 

Objective: To investigate the relationship between the molality and the freezing point of a solution.

Hypothesis:

In this experiment we will see how the change in freezing point of a solution lowers when more solute is added to water. When the molality of the solution is bigger, the freezing point decreases. 

We're going to place all the test tubes when different measurements of sugar in a big beaker with some ice cubes and salt. As I said before, the freezing point of water freezes at 0ºC, however, it's going to be lowered when salt is added. This is because the freezing point of solutions is all lower than that of the pure solvent. The salt dissolves into the liquid water in the ice and lowers its freezing point. This is because adding the solute will disrupt the equilibrium, the salt molecules dissolve in the water, but do not pack easily into the molecules in the solid (ice), making the freezing point of water being lowered when salt is added.

When we add more sugar, (more molality) the FP of the solution will be lowered. The molality indicates that the higher it is, the greater the freezing point is depressed, so to conclude, in this experiment the change in freezing point depression will be proportional to the molality, the higher it is, the lower FP. 

Table of results and graph:
Molalities of each sugar solution:
The first thing we need to do is calculate the moles by this formula: moles = g of sugar/ molecular mass of sucrose (MM of sucrose: 342.30).

After we calculate the moles, using the formula of molality (m): molality = moles/ kg of solvent (water – 0.005kg). We need to follow this process to get the molality of every sugar test tube.

0 g sugar in 5.0 g water – Pure water so à 0 mol/kg

0.5 g sugar in 5.0 g water – (0.5/342.30) /0.005= 0.001/0.005= 0.2 mol/ kg

1.0 g sugar in 5.0 g water – (1.0/ 342-30) /0.005= 0.003/ 0.005= 0.6 mol/ kg

1.5 g sugar in 5.0 g water – (1.5/342.30) /0.005= 0.004/ 0.005= 0.8 mol/ kg

2.0 g sugar in 5.0 g water – (2.0/342.30) /0.005= 0.006/ 0.005= 1.2 mol/ kg

2.5 g sugar in 5.0 g water – (2.5/342.30) /0.005= 0.007/0.005= 1.4 mol/ kg

Table:

Mass of sugar in solution (g)	Molality (mol/kg)	Attempt 1 - Freezing point (oC)	Attempt 2 - Freezing point (oC)	Average freezing point (oC)	Change in freezing point compared to pure water (oC)
0	0	- 0	- 0.6	0.3	-0.3
0.5	0.2	- 0.6	- 0.8	0.7	-0.37
1.0	0.6	- 0.3	- 0.1	0.2	-1.12
1.5	0.8	- 1.7	- 1.7	1.7	-1.49
2.0	1.2	- 2.0	- 2.2	2.1	-2. 23
2.5	1.4	- 2.9	- 2.5	2.7	-2.60

Graph:

Conclusion (explaining the results and how they match to our hypothesis):

While completing the table and creating the graph we've noticed that as the molality increases, the freezing point depression decreases (ºC). When for example the molality is 0,2, the FP is of -0,37 and when the molality is 1,4, the FP is -2,60. This clearly shows what we've said, and this is because the freezing point depression is directly proportional to the molality of the solute.  While more mass of sugar is added, more molality there's in the solution. When more molality, the change in freezing point is going to be lowered. 

A point to take into consideration is the position of the table. The freezing point depression is negative, that's why the molality, which is positive is in the upper part of the graph, and all the dots go down in the graph when the molality is bigger and the freezing point depression is lowered 

According to the hypothesis and the background information , the results obtained match with what we said before in the hypothesis

Evaluation (Discussing problems and suggesting improvements):

Generally, we think we worked well as a group and we haven't committed big or notable errors that are lately seen in the results. However, as in every lab experiment we had some strong and weak points;

On one hand, there were few strong points such as when calculating the temperature, we were aware that it remained constant and didn't change and when we were sure about this, we took out the thermometer form the cold or ice. Also, we were very precise at the time of getting the correct measurements. We followed the measurements that were in the method exactly as they were. We get the amount of water needed and all the elements we needed to use. We were extremely careful in this part because in other experiments, not taking perfectly and carefully the right measurements caused a complete disaster and non-sense results.

On the other hand, during the experiment we had some weak points. Having weak points in an experiment is normal because in the lab the're involved lots of factors that makes it easier to get a mistake. For, the next lab session we should learn about these small mistakes and correct them:
Firstly, we had some problems, as we didn´t know when we had to take out the thermometer. We didn’t know when it had reached the freezing point, so we had to repeat it a few times. Then, the way of calculating the temperature with those thermometers and continuously taking out from the solution and putting again in, is not a very precise and accurate way of completing and getting the freezing point of a solution. That way, the results must vary from other groups experiments and might not be as accurate as we wanted them to be.

We could improve this weaks points for the next lab session by finding a new method or way of calculating temperature. Maybe putting the solution at a fridge or something that maintains constant the temperature we need to reach, this is another easy and better way.

References:

Chemwiki.ucdavis.edu, (2015). Freezing Point Depression - Chemwiki. [online] Available at: http://chemwiki.ucdavis.edu/Physical_Chemistry/Physical_Properties_of_Matter/Solutions_and_Mixtures/Colligative_Properties/Freezing_Point_Depression [Accessed 19 Feb. 2015]. 

All-science-fair-projects.com,. (2015). Science Fair Projects - The effect of salt and sugar on the freezing point of water. Retrieved 19 February 2015, from http://www.all-science-fair-projects.com/print_project_1151_38