Science Buddies: "Ask an Expert"

I am working on a chemiluminescence lab and I am having a bit of trouble finding my uncertaitnies. In this lab i was required to find a correlation between the percentage of bleach and the amount of lux produced when it is reacted with Luminol, with a vernier light sensor. I used household bleach which is at 6% and diluted it separately by pouring 10mL, 9mL, 8mL, 7mL, 6mL, 1mL, and finally 0mL of the bleach into 6 different containers and then filled the difference to 10mL with water. The maximum lux produced with each new percentage was as follows:
6% 48.3
5.4% 40.7
4.8% 104.5
4.2% 40.3
3.6% 34.9
0.6% 23.9
0% 8.9

Now it is time to graph this raw data (ignoring 4.8%) and my problem is that I have no idea how to find the uncertainty of either the percentage of bleach or the lux produced and I need the uncertainties to from error bars on my graph and then best fit lines. Any help would be greatly appreciated.

Hi luminol22,

Have you done multiple trials of each experiment? In order to calculate the variability (which is how I'm interpreting "uncertainty") in your results, you will need to replicate each experiment three or more times. Then you can calculate the standard deviation of the lux you measure each time you do the experiment for a given bleach dilution. You would then graph the mean lux you measure for each dilution and then do error bars of +/- one standard deviation.

Post back if you have other questions