Practical on determinig if a burette is more accurate

  • Thread starter Thread starter lionely
  • Start date Start date
  • Tags Tags
    Practical
Click For Summary

Discussion Overview

The discussion revolves around a practical experiment aimed at determining the accuracy of a burette compared to a measuring cylinder. Participants explore the methodology, data analysis, and the significance of various graphs to be plotted based on experimental results.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions the purpose of plotting the volume of water delivered against the volume collected, seeking clarification on its significance.
  • Another participant suggests that if the devices were perfect, the two volumes should match, indicating that discrepancies can be highlighted through the graph.
  • A participant expresses confusion about how the gradient of the graph relates to determining accuracy, questioning the implications of a non-linear relationship.
  • There is a suggestion that the analysis of actual data is crucial for the lab report, emphasizing the importance of data in experimental science.
  • One participant asks whether a line of best fit is necessary for the third graph, indicating uncertainty about the analysis process.
  • Another participant advises plotting points and calculating the R² value, but also suggests that it may not be essential for the analysis.
  • A participant expresses unfamiliarity with the R² value, indicating a lack of prior experience with such analyses in their studies.
  • There is a discussion about the significance of the first two graphs in assessing the uniformity of drop sizes and the potential for systematic errors.
  • One participant reflects on the nature of experimental procedures, suggesting that students should focus on validation rather than merely following procedures.
  • Another participant raises the question of how to evaluate the performance of the measuring devices and what criteria to use for such assessments.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding the analysis of the graphs and the significance of the data. There is no consensus on the necessity of the third graph or the interpretation of the results, indicating multiple competing views and ongoing uncertainty.

Contextual Notes

Some participants indicate limitations in their understanding of statistical measures like R², and there are unresolved questions about the implications of the experimental results and the analysis methods to be employed.

lionely
Messages
574
Reaction score
2

Homework Statement



Practical on determining if a burette is more accurate than a measuring cylinder

Method: The burette was filled to a mark above 45cm3 with water and the reading recorded. The burette was opened and 30 drops of water were allowed to be delivered into the measuring cylinder, and the reading on the burette recorded. The volume of water in the measuring cylinder was recorded. The readings were recorded to two decimal places, these steps were then repeated allowing 60,90,120 and 150 drops of water to be delivered and the results tabulated.

Now I was asked to plot three graphs

i) Volume of liquid delivered from burette vs # of drops and Volume of liquid collected by cylinder vs # of drops on the same graph leaf.

ii) A graph of burette volume delivered Vs Volume of liquid collected in cylinder.

I don't see the point of the third graph, what's the point of plotting the volume of water delivered vs the volume of liquid collected? Could someone please explain this to me?

Oh and for the first graph , I took two gradients for each line, and compare how they close they were. For the burette I got .046cm3 and .047cm3 and for the cylinder .049 and 0.040. So since the gradients for the burettes were closer it should be more accurate right? Oh and the reason why my measuring cylinder gradient is so messed up is due to errors, in doing the experiment my partner was impatient so the rate at which the drops fell from the burette were not constant.
 
Last edited:
Physics news on Phys.org
If the devices were perfect the two volumes should be identical ... but this graph will highlight any discrepancy.
 
You mean by taking the gradient it should come to say.. 1? But if it doesn't how does it show which is more accurate , i don't get it :S
 
If the graph is perfectly linear there may not be a way to tell - but for your lab report you must carry out an analysis of the actual data.

Data is king!
 
So I wasn't supposed to draw a line of best fit for the 3rd graph?
 
I would just plot the points ... the best fit line may be interesting, so also calculate the R^2 for it.

Then write study it and decide what it means. Good luck!
 
Umm What is the R^2, I'm only in grade 13, I haven't done any labs needing R^2 before, and I don't recall seeing anything like this in maths.
 
The least squares best linear fit will calclate a correlation coefficient called R^2. If not, forget it.
 
Okay just to be clear, I shouldn't think about the R^2 value and for the graph of the volumes of the drops against each other, should I just find the gradient? If the gradient is almost the same that should indicate the precision to which the experiment was carried out with? I'm still a bit lost with what to do with the third graph!
 
  • #10
I would say the first two graphs are capable of telling you whether the drops are uniform (same volume/drop) so look for any trends in the graph like systematic slight curvature. Though if there is any that could have more than one explanation!

The last graph just compares now well the two devices give the same result. Notice any drop size variation is canceled out. So although in theory the information is all in the first two graphs, something is visible in the third one that is less evident than in the first two.

Maybe you thought they were looking for something more clever that stopped you having these simple thoughts?

One mistake students of experimental sciences make is to think of the procedures as rituals, that if you are terribly careful about the procedures and careful exact right volumes or number of drops or whatever that guarantees you truth and success. Instead they need to learn to think about validation. What really guarantees that this and that experiment or measurement is telling me what I think/they me what I think it tells? That my instruments are telling me the truth, if if necessary what do I have to do to know this? Maybe they are trying to put over this idea.

You might or you might not be able to say something (which you pretty well guess anyway) about which device is better or worse that the other and in what way. How would you decide how good either of these devices are anyway?

I hope this compensates you a bit for such a dull experiment! :biggrin:
 

Similar threads

Speed of Reaction Application Question
  • · Replies 18 ·
Replies
18
Views
5K
Describe the relationship between temperature and specific volume?
  • · Replies 11 ·
Replies
11
Views
4K
Predicting Remaining Pressure in Compressed Gas Cylinder
  • · Replies 3 ·
Replies
3
Views
3K
Measuring the Discharge Coefficients of a Rocket Injector
  • · Replies 2 ·
Replies
2
Views
3K
Determining the Density of Water
  • · Replies 5 ·
Replies
5
Views
7K
Coursework help - Stokes Law equation + graphs
  • · Replies 3 ·
Replies
3
Views
5K
Question on FrankHertz Experiment :/
  • · Replies 4 ·
Replies
4
Views
2K
High School Infrared Detectors & The 2nd Law of Thermodynamics
  • · Replies 152 ·
6
Replies
152
Views
11K
Undergrad Atmospheric humidity for water production.
  • · Replies 3 ·
Replies
3
Views
3K
Graduate Radius of ice melted by heat from a point.
  • · Replies 9 ·
Replies
9
Views
4K