Science Buddies: "Ask an Expert"

I am doing the project "does soil effect the pH of water." I was wondering if my pH meter was sensitive enough. It's a needle point ranged 3 to 10. It has marks in between the numbers. Will this be good enough?

Thank you for your help.

Sounds like a good meter. If your experiment results in big differences you will certainly be able to measure them. If the differences are small you might not notice. Test the meter out with some solutions you know are different pH to make sure its working.

Hi!
I also agree, you should definitely test some simple acids and bases to see if the pH meter can readily differentiate between different pHs. here's a link of common substances and their pHs (it is on the botton of this page when you go to this website)
http://www.visionlearning.com/library/m ... php?mid=58
hope this helps, good luck!

Hi jumpingjackalope, the advice given by the experts above is very good, here is some additional info and a couple more suggestions. Do you have an operation manual for the pH meter you are using? This will provide information about the instrument's sensitivity and the level of accuracy / precision you can expect. If you don't have the manual you may be able to find it online by entering "manufacturer model # manual" into an internet search engine.

Many pH meters can be calibrated for a specific pH range prior to sample testing (a procedure similar to the other experts' advice). Calibration is achieved by measuring the pH of 2 reference solutions of known pH. One reference solution will have a pH higher than your expected sample pH and the other will be lower. These 2 points will set the limits of your calibrated measurement range and any sample measurement that falls within this range will be accurate. I'm not sure if the meter you're using has this function, but if you post the model number I'd be happy to take a look. If the meter can't be calibrated I would suggest measuring and recording the pH of 2 reference solutions (high and low as above) each time you test samples. This will allow you to consider any variability in pH that is caused by the meter when interpreting the data from your experiment.

pH is affected not only by the solutes in water but also by temperature. Many pH meters have a temperature compensation function to account for this. If the meter does not have this feature you will want to make sure you take all of your measurements at the same temperature. This will increase the accuracy of your measurements.

I hope this helps, let us know if you have any more questions and keep us posted!

- Ryan