Preliminary Results
Preliminary Graph
Explanation: What happens is when both hydrogen and sodium thiosulphate react they release a chemical which starts to make more and more cloudy. So, when the cross isn’t visible by the naked eye anymore (from a clear to cloudy solution) I then stop the timer. This will then give us the time it took for each experiment’s (six in total) reaction to go cloudy. In effect, since I want to work out the rate of reaction, I stopped all the experiments near enough at the same time allowing some room for human error as it is being judged on the basis of how accurate our eye site is. Therefore, I should get a pattern of results, which match up.
Variable/s: The ideas I came up with for the variable factors were:
The quantity of either the acid or sodium thiosulphate- which would affect the experiment by either slowing it down because if there is more acid, then there is more acid particles to react with, therefore less time is necessary, but if there is more sodium thiosulphate then it will take longer for the reaction to end as there is more to react with.
The temperature C-which would then speed the reaction down as the acid particles would be heated up, and thus given more energy, so they will be moving faster and therefore more likely to react with the sodium thiosulphate quicker.
Also there was concentration-which could affect the experiment in either way (make it slower or faster) as if there is less acid particles of the given volume of solution, then there is less acid to react with the sodium thiosulphate, if there is more acid particles in the given volume of solution then it would be quicker as there is more to react with the sodium thiosulphate.
I chose concentrations ultimately as I though it would be most practical considering the time factor along with the accuracy and precision factor. For concentrations we had to work out the volume of solution for each experiment. Here are the concentrations given in table format:
M=mole, which the means the units used for the concentration of acid.
Fairness: I will make the test fair by measuring the solution of both, sodium thiosulphate and the acid is of 20cm3 and no less. As for the temperature C, that will be at room temperature C.
Safety: To make this test safe I will conduct this experiment as far as possible from the edge, so nothing spills. Also I will have goggles on at all times for the protection of my eyes.
Secondary sources: the secondary sources I used in this investigation will be listed in bullet point form:
- www.gcsechemistry.com
- CGP Double Science Award book
- Chemistry Nelson Science
- www.chlor-chemicals.com/Products/HCl/hclint.htm
Results:
As you can see from the results that each section has two results. That is because I did the experiment twice to get an accurate average. Below is the table drawn again with just the averages.
I shall now plot graph to present my results and the analyse them.
Conclusion: On the whole I would say that my prediction was correct, which was that if the concentration of the acid would be directly proportional to the length of time. Obviously my results are not entirely correct based on certain other factors. Also the line of best fit was drawn to what my prediction was. Most of my results were close to the line of best fit and did not vary too much. But there was one result that did not match in particular that did vary a considerable amount more than the others, which were circled. Reasons why it varied considerable amount more than the other results could depend upon many factors, for example, just someone walking by may have heightened the room temperature to a certain degree, or performing an experiment, and the gas leaked and affected my results. To control this unexpected variable I would have to conduct this experiment in an isolated environment where there are no outside distractions/influences.
Evaluation: I consider my evidence (results) to be reliable and non-reliable. I think this because if it is just to see what happens then my results are quite reliable, but then if my results were purely based for scientific purposes, then the manner I conducted it in had to many variables beyond my control. For example:
- Room temperature means anything between 19-21 Celsius. To improve I would need to have a set temperature with no influences.
- Surface areas of sodium thiosulphate were not the same, so based on collision theory the smaller that are the longer it takes as it is more difficult for acidic particles to reach it.
- There is always the factor of human error, which can be minimised with precautions but not demolished. The precautions we could take could be wash everything we used to make sure it is neutralised etc.
As I said earlier in the conclusion there was one result that varied to an exceptional amount, which was circled. Possible factors that may have had an effect on this were, the temperature, the sodium thiosulphate, environment form where the sodium thiosulphate came from e
The two sets of results I achieved were very similar, but there were some with a bit more varied differences. On the whole they were quite accurate. There some, which went completely wrong that, is why we have the averages.
I could have also taken another set of initial results, but It would have to have been 15 second, as more time passes the longer time it takes to react as there is less to react with.. that would have given me even more accurate readings to a certain extent.
If I went further with this experiment, I would try and find out how much concentration of acid it would take to react with one gram of sodium thiosulphate. To work it out I would either have to use the method of trial and error, or work out how the gas given off is linked with what I need to work out. If I did do this experiment successfully I would’ve shown how long it would take for one gram to react.
The usefulness with this would be that we would know how much acid to put in and not waste any, as an added bonus, the solution should become neutralised, as there would be only enough particles to react with enough sodium thiosulphate, so the acidic and calcium particles should react and go, therefore leaving water which is not harmful either. The downside would be, if you were testing the speed, the more acidic particles there are, the more area they cover, therefore reacting with the reactant much quicker.