I'm doing a project in junior year chemistry where I get to choose what I investigate as long as it covers course content. I'm interested in exploring how quantitative (ig. incremental) change in an independent variable of soil would change some dependent variable -- particularly through experimentation.

I was thinking of seeing how changes in soil pH affect soil fertility, with specifically focusing on phosphate content to measure soil fertility for simplicity + it's the easiest (i think) to do an experiment over. However I'm not sure if there's correlation between these two variables (which wouldn't look good).

Any recommendations for independent/dependent variables with correlation + a useful for real-world application of soil chemistry to look into, where a high school level experiment could produce useful observations, would be super appreciated. That's if you think my original phosphate x pH idea wouldn't make sense.

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    $\begingroup$ I understood : fixed variable and adjusted variable... I didn't understand the dependent/independent terminology. Do you mean that you would want to use a soil with the same Phosphate content, and vary the pH and see how fast cress grows? it's difficult to make a difference between phosphate and other soil minerals if they are all necessarily there. $\endgroup$ Dec 16 '20 at 20:15
  • $\begingroup$ If you vary phosphate , you are varying fertility , not just pH. $\endgroup$ Dec 16 '20 at 21:41
  • $\begingroup$ A few thoughts that might clear up: first off, you're talking high school chemistry, yes? Junior could theoretically be university. And you're talking about first year intro chem, not like AP or anything else more advanced? Just helps to get an idea of what a teacher may want. $\endgroup$ Dec 17 '20 at 6:42
  • $\begingroup$ Now I'd think usually in a high school science experiment, you're not expected to KNOW there's a connection between two variables, but to see if there is one. So I don't think it'd particularly look bad if you found no correlation between two variables, high school experiments should find that quite often (that's science... it may not be the most interesting result, but it still says something... then you try to explain why there's no connection). $\endgroup$ Dec 17 '20 at 6:47
  • $\begingroup$ Certainly if you go in with 2 variables and a fair conjecture of why you'd think they may be related (so you're not just picking 2 absolutely wild variables for no good reason), that's reasonable work to me... and I've definitely judged science fair projects that weren't so rigorous, just choosing a wider group of random variables, looking for connection without much rationale, and still seemed decent too. Certainly eye-opening connections are more exciting, and often win fairs, but science is science, and I'd hope the teacher grades a null result just as high if it's presented\reasoned well. $\endgroup$ Dec 17 '20 at 7:23

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