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felixjmorgan
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I have been doing a chemistry courseowrk, and i was wondering what i could add to get a better grade. I have not done very well so far, but i cant think what to add. Help appreciated:


Introduction

In this coursework I will study how concentration affects the rate of reaction. I will do so by timing the reaction of Sodium Thiosulphate with an acid.
In this coursework I will include background knowledge, prediction, safety, results, calculations, graphs, an analysis, conclusion and an evaluation. In my evaluation I will comment on how reliable my results were and how I could have improved my coursework in any possible way.

Background Knowledge

The definition of rate of reaction is ‘The speed at which a chemical reaction takes place. It is usually expressed in terms of the concentration (e.g.- moles per litre) of a reactant consumed, or product formed in unit time ; so the units would be moles per litre per second (mol 1-1 s-1). It may be affected by the concentration of reactants, the temperature of reactants, and the presence of a catalyst. In a higher concentration there are more Sodium Thiosulphate particles. This means there is a higher number of collisions which will have sufficient energy to react (Activation Energy). Consequently the rate increases. The time it takes for a change to take place can be measured and the rate of reaction can be approximated by taking the reciprocal of this time (1/time). For a reaction to take place 2 reactants must collide and the collision must have sufficient energy.


Prediction

I predict that as the concentration of the Sodium Thiosulphate increases the rate of reaction will increase. This can be justified by relating to the collision theory. I predict that as concentration is doubled the amount of time taken for the reaction is halved.

Safety

There are lots of safety issues to be considered while doing this experiment. These include:
Wearing safety goggles in case harmful acids (such as Hydrochloric acid- HCl) are spilt, as they would cause serious damage to the skin and eyes.
Ties and long hair should be kept away from the experiment.
Bags and other obstructions should be kept out of the way so as not to hinder the person doing the experiment.


Method

A beaker will be filled with 50 cm3 of Sodium Thiosulphate which is then measured using a burette. The beaker will be placed on a single sheet of paper with a cross drawn on it using a marker pen. 5cm3 of Hydrochloric Acid will also be measured using a graduated pipette, and added to the solution of Sodium Thiosulphate. The time taken for solution to obscure the cross is recorded using a stopwatch. This process is repeated for each concentration. I will ensure it is a fair test by only varying the concentration of the Sodium
Thiosulphate solution. This will ensure that the results are valid by keeping the concentration as the only variable.I will conduct all the tests at room temperature because temperature has an effect on the rate of the reaction. The measures of Hydrochloric acid will all be the same (5cm3). I will ensure the total volume is constant because it will always be 50cm3 . I will reduce the volume of Sodium Thiosulphate by 5cm3 each time, and I will keep the volume at 50cm3 by adding the necessary volume of water. The person timing the experiment will look for the disappearance of the cross, otherwise there would be a time lapse between seeing the cross disappear and telling the other person to stop the clock and then eventually stopping the clock.


The apparatus we will use are:
Beaker
Burette
Sheet of paper with a cross drawn on using a black marker.
Graduated pipette
Digital Stopwatch - accuracy
Sodium Thiosulphate (50g/dm3)
Water (H2O)
Hydrochloric Acid

I have done a preliminary experiment to help me decide the range of concentrations to use and how much of a difference in concentration to leave between each one. My results showed that 0g/dm3 will have an infinite reaction time. This is because Sodium Thiosulphate is needed for the reaction to take place, but in 0g/dm3 there is no Sodium Thiosulphate. My preliminary results also show that 5g/dm3 is a low enough concentration to begin with. This is due to two reasons:
We are time permitted with our experiment, and at 5g/dm3 the time taken for the reaction to take place was 403.2 seconds. We can tell from the trend of times that the time taken will be longer for a lower time. Therefore, we would not have enough time to go any lower.
We took 10 concentrations in the preliminary already, and this should show enough of a trend already, so there is no need to do an even lower concentration, as it would not help our experiment in any way.


Results

Preliminary Results Table

Sodium Thiosulphate + water (cm3) Concentration of Sodium Thiosulphate (g/dm3) HCl (cm3) Time (s) 1/time
50 + 0 50 5.0 12.73 0.078
45 + 5 45 5.0 19.16 0.052
40 + 10 40 5.0 20.21 0.049
35 + 15 35 5.0 25.86 0.038
30 + 20 30 5.0 32.13 0.031
25 + 25 25 5.0 40.42 0.024
20 + 30 20 5.0 57.29 0.017
15 + 35 15 5.0 81.34 0.012
10 + 40 10 5.0 139.27 0.007
5 + 45 5 5.0 403.20 0.002


Results
Sodium Thiosulphate + water (cm3) Concentration of Sodium Thiosulphate (g/dm3) HCl(cm3) Time(s) 1/time
50 + 0 50 5.0 13.64 0.073
45 + 5 45 5.0 19.75 0.05
40 + 10 40 5.0 22.50 0.044
35 + 15 35 5.0 25.63 0.039
30 + 20 30 5.0 28.24 0.035
25 + 25 25 5.0 37.47 0.027
20 + 30 20 5.0 48.72 0.049
15 + 35 15 5.0 63.87 0.016
10 + 40 10 5.0 142.43 0.007
5 + 45 5 5.0 352.64 0.003


Average Times

Sodium Thiosulphate + water (cm3) Concentration of Sodium Thiosulphate (g/dm3) HCL(cm3) Time(s) 1/time
50 + 0 50 5.0 13.96 0.072
45 + 5 45 5.0 19.17 0.052
40 + 10 40 5.0 20.62 0.048
35 + 15 35 5.0 24.98 0.040
30 + 20 30 5.0 29.34 0.034
25 + 25 25 5.0 37.07 0.027
20 + 30 20 5.0 48.59 0.021
15 + 35 15 5.0 65.69 0.015
10 + 40 10 5.0 127.81 0.008
5 + 45 5 5.0 378.14 0.003



Analysis
(graphs are on separate sheets)

My results show that as concentration decreases, time increases. This can be explained using the collision theory.
The rate of reaction is the speed at which a chemical reaction takes place. It is usually expressed in terms of the concentration (e.g.- moles per litre) of a reactant consumed, or product formed in unit time. Therefore the units would be moles per litre per second (mol 1-1 s-1). It may be affected by the concentration of reactants, the temperature of reactants, and the presence of a catalyst. Increasing the concentration means there are more collisions and more fruitful collisions. Consequently the rate increases. The time it takes for a change to take place can be measured and the rate of reaction can be approximated by

taking the reciprocal of this time (1/time). For a reaction to take place 2 reactants must collide and the collision must have sufficient energy. In the higher concentration there are more particles, so there is a higher chance of a reaction with the necessary amount of energy occurring. My prediction was correct to a certain extent, as I predicted that as concentration increased the time taken decreased. However, I was not entirely correct as I predicted that time taken would double when concentration halved, but this was incorrect. When concentration was 40g/dm3 the average time was 20.62 seconds, but when concentration was 20g/dm3 the average time was 48.59. This is not half the time, but it was quite close. This may be because my prediction was incorrect, but it may also be due to human error in the measuring of the liquids or the timing.


Evaluation

I think the experiment was very successful. All my results support my prediction, and I did not have any anomalous results. I was very careful measuring the chemicals out, so I believe this is why I did not have any. I would have been able to improve the experiment by letting the Sodium Thiosulphate solution drip through drop by drop from the beginning instead of letting it rush through until 20cm3 had gone through, and then doing it drop by
drop. This will have meant I was guaranteed not to add too much. I could not
do this due to time restrictions. I would also have liked a more specific definition of changing colour, as it was a bit indefinite as to when the solution had turned pink. This would have made my results more accurate. It was a fair test, because my only variable was the concentration of the Sodium Thiosulphate solution. I would have liked to repeat the experiment again to confirm my results if I had had more time to do so. Also, if we had had more time I would have liked to use a wider range of concentrations to see if the patterns that have developed continued.


Conclusion

Overall I think that this experiment was a success as I have proved that concentration does affect rate, and I have also found that when the concentration is doubled the rate of reaction is halved. I think I could have improved my investigation by:
Obtaining more results to get a better overall result.
Take times for a lower concentration than 5cm3 (we could not due to time restrictions).
I used ICT to display my coursework, but I did not use it in anyway that affected the experiment.
I would like to do a further experiment to confirm my results. However I am restricted by time and the available facilities which means I cannot repeat it.
My results matched my prediction.
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felixjmorgan
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cmon people. i really need help!
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Cate
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I did chemistry GCSE last year, and I found the coursework a pain too, but I managed OK (86% for my coursework, 3 marks off an A for the exam). Just as a general pointer, it makes the whole piece a lot clearer if you organise it as follows:

Introduction - say what you are going to investigate, and include background information about the theory etc. You don't need to include 'In this coursework I will include background knowledge, prediction, safety, results, calculations, graphs, an analysis, conclusion and an evaluation. In my evaluation I will comment on how reliable my results were and how I could have improved my coursework in any possible way.' it's a waste of space.

Method - say how you are going to carry out the experiment, pointing out dependant and independant variables and how you are going to control them etc

Graph of results - put all raw data in an appendix, as this makes the piece flow better and clearer

Discussion - discuss what the graph shows, then possible reasons for why it shows whatever it shows. Try and include as much science as possible to get the best marks

Conclusion - write up your conclusion for the experiment, and include why you came to that conclusion

Evaluation - write up how you thought the experiment went, what you thought could have been done better, what went wrong, if anything. Also, to get the best marks, you should suggest an idea for a further related experiment, and include how you would carry it out, with enough information so that a person could do the experiment from your description.

Appenidices - all raw data, books you used, etc.

Hope this helps!
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username9816
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(Original post by Cate)
I did chemistry GCSE last year, and I found the coursework a pain too, but I managed OK (86% for my coursework, 3 marks off an A for the exam). Just as a general pointer, it makes the whole piece a lot clearer if you organise it as follows:

Introduction - say what you are going to investigate, and include background information about the theory etc. You don't need to include 'In this coursework I will include background knowledge, prediction, safety, results, calculations, graphs, an analysis, conclusion and an evaluation. In my evaluation I will comment on how reliable my results were and how I could have improved my coursework in any possible way.' it's a waste of space.

Method - say how you are going to carry out the experiment, pointing out dependant and independant variables and how you are going to control them etc

Graph of results - put all raw data in an appendix, as this makes the piece flow better and clearer

Discussion - discuss what the graph shows, then possible reasons for why it shows whatever it shows. Try and include as much science as possible to get the best marks

Conclusion - write up your conclusion for the experiment, and include why you came to that conclusion

Evaluation - write up how you thought the experiment went, what you thought could have been done better, what went wrong, if anything. Also, to get the best marks, you should suggest an idea for a further related experiment, and include how you would carry it out, with enough information so that a person could do the experiment from your description.

Appenidices - all raw data, books you used, etc.

Hope this helps!
noone in our skool ever had appendices in their science coursework!!
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jediknight007
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Dunno whether it's worth it but you could say what size beakers and burettes you are using and what degree of accuracy you used. Also, you could explain in your evaluation, if you haven't yet done so, any possible errors which could have occured and what effect they would have had on your result. For example, measuring less acid than you should have would have meant a slower rate of reaction etc...
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Dickie
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ooh! im doing this piece of coursework now too!

well, *should* be doing it
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Harry Potter
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Do you have the mark scheme? If so, make sure you have every point on the mark scheme. If you've done that, then you're probably just not going into enough detail. For example, I think you probably need to write a bit more theory about collisions and things if you want to get the 'uses detailed scientific knowledge to make an informed plan and valid prediction' mark (that's not the correct wording and you might have a diff. board btw.).
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thefish_uk
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(Original post by Harry Potter)
Do you have the mark scheme? If so, make sure you have every point on the mark scheme. If you've done that, then you're probably just not going into enough detail. For example, I think you probably need to write a bit more theory about collisions and things if you want to get the 'uses detailed scientific knowledge to make an informed plan and valid prediction' mark (that's not the correct wording and you might have a diff. board btw.).
All the exam boards have the same mark scheme, for GCSE at least.

You need detailed knowledge on collision theory in your Analysis, maybe with diagrams.
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Harry Potter
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(Original post by thefish_uk)
All the exam boards have the same mark scheme, for GCSE at least.
Ah.

(Original post by thefish_uk)
You need detailed knowledge on collision theory in your Analysis, maybe with diagrams.
Yeah. I just copied and pasted the theory from my planning into analysis and changed it too the past tence, but I'm not sure if this is advisable.
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thefish_uk
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(Original post by Harry Potter)
Yeah. I just copied and pasted the theory from my planning into analysis and changed it too the past tence, but I'm not sure if this is advisable.
I put loads in. You need it to make sure you get a good mark, I think. All well explained.
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rudro_in_paris
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Yeh i gotta do my chmeistry coursework as well...it is soo hard and quite annoyin....mine's due on tuesday and i haven't even started yet!!
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yusufu
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(Original post by Harry Potter)
Ah.



Yeah. I just copied and pasted the theory from my planning into analysis and changed it too the past tence, but I'm not sure if this is advisable.
That is most advisable, as long as the theory in the planning is correct
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]{ingnik
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shouldn't you be talking about other factors that affect rates of reaction and how you are controlling them? scuse me if u already have, i only skimmed it.
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yusufu
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Your evaluation needs a lot more work.

Add more detail for your further work.e.g. predict something, give a range.
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2 boy luver
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undefined
(Original post by bono)
noone in our skool ever had appendices in their science coursework!!
Im doin dis in skool! Our teacher asked uz 2 find sum reasearch on d net 2 help uz wif our coursework!!! And dis waz d site i found most helped me!! Thank uuuuuuu!!! :cool: I'll b returning! Lv ya xxx
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Renaissance_boy
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first of all move this post to acadamec, coursework etc.... forum!
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Sasuke!
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i rememebr i did this coursework and got pretty good, but i cant rememebr as i did it last year also i wouldnt put the whole coursework on here as people may copy it i got 18% out of the 20% for the rates of reatcion and resistance of a wire
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