An increase in the rate of collision or the rate of reaction can be achieved by increasing the concentration, pressure, or surface area
List of Apparatus:
- 2 Beakers,
- 1 measuring cylinder,
- 2 Boiling tubes,
- Paper with ‘X marks the spot’,
- Hydrochloric acid,
- Thiosulphate,
- Stopwatch,
- Spatula,
- Conical flask,
- Thermometer,
Method:
These are the steps, and the reasons, in which I will take in order to complete my experiment and to get my preliminary results:
- To begin with I will set my equipment that will help me accomplish my results. The equipments I will be using are listed on my “list of apparatus”. Also alongside my equipment I will get the Thiosulphate and the Hydrochloric acid.
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As my second step I will get the tube of water and pour boiled water into it, which then means that I must wait until the temperature falls down to the point at which I want to begin at – 70oC and the work my way down to 20oC.
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I will now measure the amount of Thiosulphate and Hydrochloric acid I will use and keep it constant. I will use 10cm3 of Hydrochloric acid and 20cm3 of Thiosulphate and then place them in separate beakers after setting their temperature to where I would like them.
- I will then pour both of them into the conical flask and stir them (5 times) using the spatula.
- As soon as I’ve done that I will start the stopwatch and wait until the ‘X’ disappears, which the time point at which the stopwatch will be stopped.
Fair Testing:
In order for my findings to be valid the experiment, I must keep my experiment as fair as I can. I will use the same standard each time for judging when the X has disappeared; I will do this by using the same person during the investigation.
I will make sure that I use the measuring cylinders for the HCl and Thiosulphate; this will help give the same reading measurements.
The amount of HCl will be 10cm3 each time, and the amount of Thiosulphate will be 20cm3.
During the increasing/decreasing stage of the experiment, where I will increase or decrease the temperature of the water, I will use the same beaker to pour the additional water into the water tube.
All of these precautions will make my final results more dependable.
Key Factors:
During this investigation I will vary the temperature to see if it will have an effect on the rate of reaction.
As a result the key factors that will change will be the temperature and the time at which the ‘X’ disappears. I will control the Thiosulphate and the HCL and keep them constant.
To help make this a more reliable investigation, I will repeat the experiment more then 2 times, because the more repetition I make the more reliable and better the results get, this therefore helps give more meaningful evidence.
I have decided to have a range as part of this experiment. I have decided to go up in 10oC at each step, starting at 20oC and up to 70oC, because it may get dangerous above that point. This will help create an image of how the results will turn out to be.
Analysis
I know that surface area, pressure, concentration and temperature are all factors that have effects on the rate of reaction, for my experiments I have chosen to investigate ‘Temperature’ and observe my results.
From my experiment I’ve established that as the temperature increases the time of the rate of reaction decreases, which makes them inversely proportional.
I’ve recorded my results onto a table and illustrated them onto a graph. While I did my graph I organised it in a way that the ‘time taken’ was on the x-axis. I also decided to do two graphs, one showing a curved line of best fit, and the other showing a straight line of best fit, which I divided 1 by the time taken to get the results.
To find out the inversely proportional results, which means I must divide 1 by the time taken, this is what I obtained:
Figures
20oC - 0.029
30oC - 0.042
40oC - 0.067
50oC - 0.086
60oC - 0.123
There are patterns and trends that I’ve found while carrying out my experiment. One of the few that I’ve found is that the time the ‘X’ took to disappear got faster as the temperature increased. Another pattern that I have found while carrying out my experiment is the way in which I found my anomaly. Each point on my graph, which represented the time taken for each temperature, had a pattern, which I thought they followed. They each increased by approximately 3 seconds, except two, which I thought to be anomalies.
Also by using the graphs, with lines of best fit, I can draw a conclusion from my experiment. Firstly I can see that with the graph which had the straight line best fit line, which plot the time taken against temperature has a negative correlation, meaning that as the temperature increased the time taken for the reaction to take place decreases, which proved that it was inversely proportional.
Although from this I also think that naturally the graph shows that the plotting rate against temperature has a positive correlation, because as the temperature increased so did the rate of reaction.
This is because when the temperature is increased the particles will have more energy and thus move faster. Therefore they will collide more often and with more energy. Particles with more energy are more likely to overcome the activation energy barrier to reaction and thus react successfully, and when solutions of reacting particles are made more concentrated there are more particles per unit volume. Collisions between reacting particles are therefore more likely to occur.
T his could be proven with the ‘Collision Theory’. This theory states that in order for a reaction to occur particles have to collide with each other. Only a small percent result in a reaction. This is due to the energy barrier to overcome. Only particles with enough energy to overcome the barrier will react after colliding. The minimum energy that a particle must have to overcome the barrier is called the ‘Activation Energy’ (or Ea). The activation energy shows that the larger activation energy is the slower rate of reaction, therefore the smaller activation energy the faster the rate of reaction.
The size of this activation energy is different for different reactions,
the graph plotting the average curved line of best fit results shows that the difference of rate between increasing temperature excluding the anomalies – 30oC and 20oC, are all close as they increase in steps of 3-4 seconds. However, there is a huge gap between the 40oC and 30oC, where the time taken increased by 9 seconds. To understand this so that it could make more sense, you must refer to the collision theory and the ‘Activation Energy’ theory (above).
Here are the results that I obtained which produced a curved line of best fit:
Average Time:
20oC – 34.98seconds
30oC – 23.98seconds,
40oC – 14.90seconds,
50oC – 11.63seconds,
60oC – 8.14seconds,
The kinetic theory explains that when particles are moving that is an increase in temperature that causes a substance to melt. As the temperature is increased the particles vibrate more vigorously, but they do not suddenly vibrate far more vigorously when a substance melts. What happens is that the vibration reaches a critical point that allows the particles to break free of their fixed positions, therefore breaks their bond.
Therefore this tells us that the greater the temperature the greater the energy in the particle is.
In my prediction I mentioned that the rate of reaction might increase as the temperature also increased, and from my preliminary experiment my prediction turned out to be successful, as it is what I had expected but I had to prove it using my final experiment.
Also another area that my prediction supported would be my graph. My graph gave me results that proved temperature and the time taken were inversely proportional; it also proves that my graph had a positive correlation on a natural basis (using the results of the curved line of best fit – I didn’t use 1 divide by time taken on this graph). My graph of inversely proportion had a negative correlation, which proves that as one increased the other decreased.
There are parts of my experiment that didn’t support my prediction, and the fact that I had anomalies within my results proved this. The reason why that may be is because there was a possibility that there would be human error (observing the ‘X’ disappear).
Therefore my conclusion supported my prediction to an extent, because it states the same points I’ve made in my prediction but in more explanation.
My preliminary experiment gave me an outline of what to expect, I repeated the experiment twice and used the same range. This gave me a pattern that I could use to check whether my experiment is going according to plan. The pattern was that as temperature increases the rate of reaction also increased.
Evaluation
On an overall view, I think my experiment was a success to an extent and the procedure I used had worked quite effectively even though there were certain things to consider and certain obstacles that got in the way. This procedure helped me obtain results and transfer them onto a graph. Therefore my experiment was accurate to a point.
The evidences that I had used were fairly good, because they gave me results as accurate as they could be. The disadvantage about this is that there were errors that had reduced the possibility of getting better results.
For instance my graph shows that some temperatures didn’t fit my pattern (anomalies), because they tended to have time limits more than the others.
From this I tried to make it better by repeating the experiment as many times as possible within the time limit that I had, but when I had obtained my results I noticed few anomalies.
The reasons why I picked up on these anomalies are because they were seemed to be slightly different compared to the others figures. For example I noticed two anomalies because I compared my 1st results of time taken for the ‘X’ to disappear to my 2nd results and didn’t use the average results. I did this because I thought it would make it more accurate and make more of a fair test.
The anomalies were the 50oC and 60oC, they both had their time figures pattern different compared to the other whom had it the same. The pattern that I am mentioning is this:
1st results: 2nd results
20oC -time=33.10secs -time=36.35secs
30oC- time=22.53secs -time=25.42secs
40oC- time=13.50secs -time=16.29secs
50oC- time=11.09secs -time=12.17secs
60oC- time=7.97secs -time=8.31secs
This shows a pattern, if you look across both the tables and compare each temperature to its time you will see that they increase approximately by 3seconds, except the 50oC and the 60oC, which have an increase between 1 and 2 seconds. Therefore because of this reason there seem to be the anomalies.
I decided to keep the concentration constant, as it wasn’t part of my investigation, and I also used substances that would help me identify the fact that the time taken decreases when the temperature increased.
I decided to use 20cm3 of Hydrochloric acid and 10cm3 of Thiosulphate acid. The reason why I kept them constant is because it is a fair test and also because if we changed the concentration then the results would be different, as each temperature would have different concentration and therefore different time taken for the ‘X’ to disappear.
I’ve also decided to do a range of each temperature and duplicates, because from my preliminary I’ve noticed that duplicates help give better results (therefore my preliminary was very useful and is supported by my conclusion).
The ranges that I’ve used go up in 10oC’s and start from 20oC up to 60oC. We used 60oC instead of 70oC because the particles react vigorously and therefore become dangerous to handle. The reason they act s o dangerously is because their speed increases rapidly (kinetic theory). It goes up in 10’s because it is easier to see differences within the results, and is also easier to work our way down the temperatures.
From my experiment I know that when Thiosulphate reacts with hydrochloric acid, a yellow cloud is formed. To get the results of this reaction you can measure how long it takes for a certain amount of sulphur to form, which is what I did. I did this by observing the reaction down through a conical flask, where there was a black cross on white paper. The mixture of Thiosulphate and hydrochloric acid eventually obscures the ‘X’.
Mix Ongoing Watch stopped
By taking these steps I’ve noticed that there were inaccuracies and that a few things that I could have done to make my experiment produce better outcomes.
For example the fact that it is easier to use mass and volume to find out whether the temperature increases or decreases the rate of reaction was one of them. This is because the mass and volume are more accurate to use and give better outcomes and are easier to use.
The reason why volume would be better to use is that when a gas is formed from the hydrochloric acid and Thiosulphate reacting, the gas could be collected in a gas syringe. The graph would therefore give an accurate measure of how fast the gas product is being formed. This gives the volume to a more accurate rate than the procedure that I used; with this you can even measure the final maximum volume of gas and the time at which the reaction stops.
The reason why the mass would be better to use, rather than observing the ‘X’ is also because it gives the results to a more accurate point. The gas would be trapped using cotton wool blocking the top, the beaker would then be placed onto a weighing scale, and the increase or decrease of the reactant would be shown, using the scale. This would then show the results accurately on the graph.
Also another way of keeping temperature the same is by using silver insulated flask, this would reflect the heat back into the flask, therefore keep it warm, and a flask makes it easier to increase or decrease the temperature by 10oC, I would simply add more hot water or cold water to the water bath. This was a problem I had, because I found it difficult to go up by 10oC which is why I didn’t use the 70oC, and 60oC instead. Where the temperature stays the same (reflected back) I could easily change the temperatures.
These are all other ways in which I could have done my experiment. Also data loggers is an additional technique to use, they could be used to give the accurate temperature of substances and even help show when to increase of decrease the temperature of the water bath (which is what I did).
An additional procedure to carry out is to use the equation to find the accurate line of best fit. I have done this and the attached paper shows my working out and the end results that I obtained, including a separate graph paper showing what it would look like from my prospective. I felt that it might be wrong; therefore I felt that being wrong would have on effect on my investigation, which is why it is on a separate paper.
Therefore in total I have produced three graphs, one shows the results and curve of best fit using my original time results, while the other shows my estimated line of best fit using my inversely proportional (1 divide by time taken) results, and lastly the third graph shows the accurate line of best fit, which I found using the equation, where my working out could be wrong. Also another thing I did was arranging my graph in a way that the y-axis recorded the time taken while the x-axis had the temperature recorded on it. This is because the time was dependent the value and temperature was the independent value.
The things that I did that will make my graph look different, is that I used the ‘average y’ and plotted it onto my graph and used the ‘0’ point on the graph as a starting point, rather than working out the ‘C’ (intercept on the axis) in the equation: ‘y=mx=c’ (y and x are both averages). I did this because the figure of ‘C’ was not meant to be over 0 or below, whereas with my working out gave me an answer over 50, which indicated to me that it was wrong.
However I believe that using that equation to get an accurate line of best fit would help improve the investigation. I did that but was unable to get the expected results. Therefore because it was wrong I will refer to both my other graphs within my investigation.
I think that my evidence is reliable because it is supported by my preliminary experiment and my prediction. Alongside my evidence I think that my results are reliable for the same reasons, and are also supported by my conclusion. Of course there are ways in which I could improve my experiment, which involve the use of other technique that give accurate results. These techniques are the ways you could do this experiment as well.