Lab Report Literature Values in IA's

[jenicalina]

Okay, I apologise in advance for creating this post which I'm sure has already been asked many times, but is there any particular resource or search term we can use to find the literature values for a Practical?

I've been trying to search for the literature value of the time taken for the complete reaction of sodium thiosulfate (Na₂S₂O₃) and hydrochloric acid (HCl) but with no luck whatsoever.

As my practical's aim is to determine how the concentration of Na₂S₂O₃ affects the rate of reaction, do I really need to find this literature value to compare with my data? I do understand its importance in the calculation of percentage error, however I'm also slightly confused as to how I would be able to calculate the % error if the literature value is for the complete reaction, and my intervals do not all result in the complete reaction (ie. there are limiting reagents due to concentration etc.)

Many thanks--

P.S.: As my teacher wants me to submit this in less than a weeks time, I'd greatly appreciate if any type of suggestions can be provided as soon as possible.

[iblyf]

Hi

Sometimes with Chem IAs there is no 'literature value' per se. Rather, you need to explain it using Topic 6- Kinetics. Basically talk about what an increase in concentration does to rate of reaction, and therefore, according to the kinetic theory (as in more particles available for collision etc.), what you should expect to happen i.e. the one with the highest concentration will have the fastest rate.

I speak from experience- I have done a very similar IA on rate, and you need to use the kinetic theory as there isn't really a lit value.

Feel free to ask me more questions- I have done 8 total science IAs (4 for bio, 4 for chem) do I have a pretty good idea of the process

Edited October 23, 2013 by iblyf

[jenicalina]

Hi

Sometimes with Chem IAs there is no 'literature value' per se. Rather, you need to explain it using Topic 6- Kinetics. Basically talk about what an increase in concentration does to rate of reaction, and therefore, according to the kinetic theory (as in more particles available for collision etc.), what you should expect to happen i.e. the one with the highest concentration will have the fastest rate.

I speak from experience- I have done a very similar IA on rate, and you need to use the kinetic theory as there isn't really a lit value.

Feel free to ask me more questions- I have done 8 total science IAs (4 for bio, 4 for chem) do I have a pretty good idea of the process

Okay, well that definitely makes life a lot better in terms of writing up this IA- however, just another question: what should I do with the calculations on percentage error?

I understand that with % error, you need the literature value in order to calculate it, and that it's also important because then with the % error you could then talk about the accuracy of your data in the IA. But if there's no such literature value to work off, then there's no method to calculate % error and therefore no way to talk about accuracy.... or is there another method/calculation I can use that still will indicate the accuracy of my results?

I know so far that with standard deviation, I can write about data variability, and with standard error, if the error bars aren't overlapping, I can mention that they are likely to be statistically significantly different. (though I know that in Chemistry IAs, there's no need to include error bars in our processed data graphs: that's only for biology and physics)

And also, just with some other questions: how long are our IAs generally supposed to be? I know that there isn't any word limit, but I had a friend of mine go up to 6,000 words... whilst mine remained at a sad 2,000.

My general (and very basic) outline for IAs is that I should have at least 1 page for my conclusion, 1+ pages for my Evaluation. I'm not quite sure how much background information I should provide, because in my opinion, I don't think it's a major focus in the IA, so generally background information falls to just under half a page or so. In terms of processed data, I've also found myself sticking to making just one processed data table, and one graph.

Should I be adding more into my IAs?

Edited October 23, 2013 by jenicalina

[iblyf]

With % error, there are many ways you can calculate it. I have personally never been taught a way that uses the literature value! Rather, I work it out using a method that I will explain in a second and then use this error alongside the measurement and the literature value that you have found (or the trend that you would expect according to the e.g. kinetic theory) to explain whether or not my results are accurate and follow what should be expected.

First of all, you are going to need to work out average uncertainty for every trial. I'm assuming that at each variant, you will have at least 3 trials, so you are going to need to determine an average uncertainty. Use the formula that (hopefully) your teacher has given you.

After you have done that (and you also have the average results for each of the trials), the percentage error for each variant will be:

(average uncertainty of the measurement) / (average measurement) x 100

For example, if you were measuring the effect of increasing the weight of Mg on its rate of reaction with HCl, if your average measurement for time at a Mg weight of 5.00g is 10.23 seconds, and your average uncertainty is 0.43 seconds, then your percentage error will be (0.43) / (10.23) x 100 = 4.2%

After you have done that, you can work out the total percentage error for rate, and then work out how much you can therefore 'add' or 'subtract' the result to compensate for uncertainties.

I'm not sure what you mean about error bars- I do both Bio and Chem and my Chem teacher has said that you have to include them for Chem too, so I would just in case- it's better to have something that you don't need than to miss something that's essential. But that's right- if the error bars overlap then the results aren't different enough to show a trend. Also, make sure that on your graph you show a linear line of best fit.

With IA length, it is much better to have quality over quantity. It depends how many IAs you have done so far, but for me my first ever one (for Bio) was around 2,000 words, but my last one that I got full marks on was around 5,600 words. With Chem though, I don't think you really should be aiming towards achieving a certain 'word count' as such. Rather, I guess words will come from understanding of your experience. If you really understand it, spend a while establishing your experiment, and have a strong analytical conclusion and evaluation you should start to pile up the word count. but, here is a quick list of what I think every good chem IA needs to have:

Design: a good intro of around half a page detailing the chemicals that you will be using and what you are measuring, clear research question that is around 1/3 of a page long that includes your IV, DV, variants, and how you will manipulate these, and how you will use the information that you have collected to calculate your DV, a hypothesis (not a part of the criteria but good to be able to refer to in your conclusion), controlled variables (all of them- they are super super super important), apparatus and method.

Data: Must have qualitative data, raw quantitative data, processed quantitative data, correct uncertainties, correct significant figures, correct data analysis and two graphs.

Conclusion and evaluation: Clear and analytical conclusion that not only summarises the data that you have- but also explain why that you have observed the result that you have. The evaluation needs to clearly detail possible errors that may have impacted on specific results, and how these can be viably improved.

I hope that helps a bit!

Edited October 24, 2013 by iblyf

[jenicalina]

Okay, I'll try that then!

Thank you so much for your help!

And yes, I actually haven't done a lot of IA's, this would be my second complete IA for Chem, in which for the first, we all have literally no idea what we were supposed to include.

All the best with your incoming exams!