 metal finishing, our readers usually leap cheerfully to help, and you'll see hundreds of examples on these pages! But it isn't within our power to clarify a homework assignment, to make up for a poor selection of books in the school library, or to answer homework questions for millions of students around the world. Further, teachers are constantly imploring us to: "Just tell the students to do their own homework!"
I couldn't agree with you more about the fact that kids try to take the easy way of finding answers. However, I have been to my local library for research questions only to find that the resources are out of date or do not go in depth enough. Then I was directed to go on line for answers. My son thought he hit a gold mine when he found all those responses and left them for me to read. I told him he had a wealth of info and to come read! He was looking for the effects of phosphoric acid on metals. His science project though stemmed from Coca-cola and the effects it had on various materials. So possibly the boy who originally asked the question might have had a broader topic. My son's teacher told him to look up acids and the effects they have on metals. That is how we got to this site.Suzy C
- Raymond, Maine
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September 21, 2008
What common acids (Lemon juice, vinegar, orange juice) will have the most effect on metals? I am a 6th grader and I am doing a science project and I have to ask a person or expert and I don't know where to go.David H
6th grade student - Apple Valley, California
September 24, 2008
Hi, David. Your question isn't tightly enough framed yet, because you haven't defined what you mean by "effect" (discolor? remove tarnish? corrode holes through? rust?) and you haven't yet specified the particular metals (for example, none of these will have any effect at all on gold).
But in general, vinegar or lemon juice will remove tarnish from copper, remove rust from steel, and corrode zinc. I don't know about orange juice.
Cut some post-1982 pennies into tiny pieces to expose the zinc core and leave them in these three materials for a week and see what effect you discover. Good luck.
Ted Mooney, P.E. RET
Brick, New Jersey
November 4, 2008
My son is also doing a science fair project using different pH's to see the effect they have on the rate of oxidation of copper and iron. We are removing the metals from their test tubes for 1/2 hr daily in order for the oxidation to occur. I'm just trying to verify that our results are correct thus far. It seems our iron isn't faring too well in the lower pH's but both the copper and the iron seem to be faring the best in the highest pH. Is this correct? Just trying to make sure we haven't goofed somewhere along the way.Sharon Kleszynski
- Manteno, Illinois
November 7, 2008
Hi, Sharon. Science is different than spelling or arithmetic; the object is not for your son to get the "right" answer like in spelling or arithmetic. The object is to learn how to form a hypothesis and to develop a test procedure that tends to confirm or disprove the hypothesis. You set up a test procedure, you honestly and accurately record your observations, and then you can try to understand and explain those observations. But your observations are non negotiable! You never ever change them even if the teacher and every other student got contrary results.
It is actually better if he doesn't know the results to expect, because then he won't be tempted to discount what he has seen, or repeat things until it turns out "right" due to some random event. If he feels pressure to get the "right" answer, he will be tempted to practice "junk science".
It really is important for him to understand the critical difference between things he has observed and his possible explanations for what he sees. Get a composition book =>
If he starts writing "... because the copper metal is being converted to copper sulphate", stop him -- because he didn't observe that, he is presuming that. He should save explanations of why until after the expe