Thank you,
Now, after I find the concentration after measuring on the calibration curve, if i put the results on a table, then should I say, for instance, "The total concentration of this sample is 16 ?" Do I say 16 micrometers? Or something else?
Idrees
Questions about How Blue is your Sport Drink?
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Re: Questions about How Blue is your Sport Drink?
Also, one more thing,
I was using a proportional calculator to find where the results would intersect with the calibration curve, but they would always be different. For example, if I used the proportion for the 4.25 micrometers, which was 794 over 4.25, if I used it to find out the proportion for 1302 over X, it wouldbe different than using the proportion 1319 over 17. Why?
Thanks, Idrees
I was using a proportional calculator to find where the results would intersect with the calibration curve, but they would always be different. For example, if I used the proportion for the 4.25 micrometers, which was 794 over 4.25, if I used it to find out the proportion for 1302 over X, it wouldbe different than using the proportion 1319 over 17. Why?
Thanks, Idrees
Re: Questions about How Blue is your Sport Drink?
And after subtracting the blank sample from the other samples with known concentration, do I do the same for the sports drinks? And do I graph the water since now it is above the other samples on the scatterplot chart?
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norman40
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Re: Questions about How Blue is your Sport Drink?
Hi Idrees,
You should report the sports drink concentrations with appropriate units. For this experiment you can use micromoles per liter (or uM/L) for the concentration units. For example you could say “the concentration for this sample is 16 uM/L” or “the concentration is 16 micromoles per liter”.
Regarding your next question, you found that the ratio of resistance/concentration was different for various samples from your calibration experiment. One explanation for this is that there’s some variation in the measurements and/or sample preparation. As a result of experimental variation, your calibration data might not form a perfect straight line. Instead, the data might “scatter” around a line. The inconsistent ratios you found might be due to this scatter.
The equation for a straight line is
Y= mX + b
where m is the slope of the line and b is the intercept (the intersection of the line and the Y-axis). You can see from this equation that the ratio Y/X is a constant (and equal to m) only if the intercept (b) is zero. In your experiment an intercept of zero implies a resistance of zero with no blue dye in the solution. Due to data scatter and some other possible factors, the intercept value for your data may not be zero. If that is the case then you will have different resistance/concentration ratios.
A better way of using the calibration data is to find the “best fit” of the data to a straight line. You can do this graphically or use a mathematical procedure called linear regression. Once you have a “best fit” line you can use the graph or linear equation to find the sports drink concentrations. Some details about the equation for a line are available at the following links.
https://www.mathsisfun.com/equation_of_line.html
https://www.mathsisfun.com/data/scatter-xy-plots.html
And about your last question. I think you should subtract the resistance for the blank sample from the sports drink readings. The purpose of subtracting the blank is to account for light loss due to the cuvette and other factors. All of these factors are present in the sports drink samples so it is appropriate to subtract the blank for these samples as well as the calibration standards.
The water sample is the blank. So the dye concentration is zero. Also, the resistance is zero after subtracting the blank from itself. My suggestion is to exclude the blank from your calibration chart.
I hope this helps. Please post again if you have more questions.
A. Norman
You should report the sports drink concentrations with appropriate units. For this experiment you can use micromoles per liter (or uM/L) for the concentration units. For example you could say “the concentration for this sample is 16 uM/L” or “the concentration is 16 micromoles per liter”.
Regarding your next question, you found that the ratio of resistance/concentration was different for various samples from your calibration experiment. One explanation for this is that there’s some variation in the measurements and/or sample preparation. As a result of experimental variation, your calibration data might not form a perfect straight line. Instead, the data might “scatter” around a line. The inconsistent ratios you found might be due to this scatter.
The equation for a straight line is
Y= mX + b
where m is the slope of the line and b is the intercept (the intersection of the line and the Y-axis). You can see from this equation that the ratio Y/X is a constant (and equal to m) only if the intercept (b) is zero. In your experiment an intercept of zero implies a resistance of zero with no blue dye in the solution. Due to data scatter and some other possible factors, the intercept value for your data may not be zero. If that is the case then you will have different resistance/concentration ratios.
A better way of using the calibration data is to find the “best fit” of the data to a straight line. You can do this graphically or use a mathematical procedure called linear regression. Once you have a “best fit” line you can use the graph or linear equation to find the sports drink concentrations. Some details about the equation for a line are available at the following links.
https://www.mathsisfun.com/equation_of_line.html
https://www.mathsisfun.com/data/scatter-xy-plots.html
And about your last question. I think you should subtract the resistance for the blank sample from the sports drink readings. The purpose of subtracting the blank is to account for light loss due to the cuvette and other factors. All of these factors are present in the sports drink samples so it is appropriate to subtract the blank for these samples as well as the calibration standards.
The water sample is the blank. So the dye concentration is zero. Also, the resistance is zero after subtracting the blank from itself. My suggestion is to exclude the blank from your calibration chart.
I hope this helps. Please post again if you have more questions.
A. Norman