Rust in saltwater vs. fresh

A. You may get faster results if you stir the water a few times a day to mix air (Oxygen) in with the water. How about you telling us the different effects saltwater and tap water have? After all, YOU are doing the experiment and the best answers come from what actually happens, not from what someone thinks SHOULD happen.:-)

A. C'mon, Michelle: knowing the expected results will corrupt the experiment :-)

That's why pharmaceutical trials must be run "double blind". If you know the "right" result it is very difficult to not overemphasize the supporting evidence and talk yourself out of recording the contradictory evidence. Have your daughter conduct the experiment exactly as the experimental procedure describes, and carefully report her results. She should get an A if she follows the instructions, accurately reports what she got, and writes it up well.

If she gets different results than the teacher wanted, what must be done is the teacher must modify the experimental procedure instructions for next time. The teacher certainly does not expect the students to falsify results to make a poor experimental procedure look good. :-)

Good luck!

A. Books can be wrong, Victoria. Properly derived experimental results, demonstrated repeatedly, are not wrong -- they are science! I have not tried steel wool myself, but I have tried nails and seen no difference in corrosion between salt water and tap water myself. Salt water is far more conductive, so when you have dissimilar metals in contact in solution, the results may be different, but I find it very believable that the salt water does not rust the steel wool faster than tap water and have seen no evidence to lead me to believe that it does.

I'd love to see the book publisher's test notes because I'll bet the publisher collected his millions of dollars to publish this stuff without even once taking 30 minutes to test what they've written. And when it's a science book they are publishing, which is about the "Scientific Method", that's little short of criminal :-)

A. You should believe your test results, Chris. And then you should run your test again to confirm them. And then do it again to be triple sure. And then the more static you get, the more you will learn and the longer you will remember it. Because when you're sure, you're sure. And there's no feeling like it, and suddenly science is fun :-)

A. Hi, Kasey. Not everybody gets the same result, but I suppose you could claim that the salt water is more conductive so it helps electrochemical reactions like rusting proceed faster. But are you sure that you'll get the same result if you repeat the experiment? What reason will you give if you get the opposite result next time?

Regards,

A. Times a-wastin', Dillion. Get those pieces of steel wool into play and let us know what you found. Good luck

Regards,

Hi, Natalie. I have opinions on your methodology: I think you should test paper clips, nails, and pennies -- each in separate jars. And I think you should rethink the hot water; how are you going to keep it hot for the week or so that you should allow for the test? It might be better to use room temperature vs. refrigerator temperature.

But I have no opinion on the results you'll get -- you'll get what you get. And what you will get is the correct answer.

Regards,

A. Hi, Brandy. Coins and nails and plastic forks and rubber bands would not be very useful if they rusted in minutes or hours. 3 days should be enough for a plain steel nail to show early signs of rusting.

Regards,

A. Hi, Luis. First, I feel you should not be browsing the internet, but instead getting help from a librarian at your school or town library to locate an age-appropriate science book.

Why? Because the internet is a gigantic disorganized mess :-) You are wandering from lecture hall to lecture hall, hearing stuff that was intended for high schoolers, and stuff that was intended for bridge designers, stuff that was intended for post doctorate corrosion engineering students, and stuff that was intended for homeowners dealing with rusty water.

You need a book that teaches you how to do science projects and why. You need to find something that details how to conduct an experiment, and then you need to do the experiment and have some confidence in your results. Once you are sure that your results are substantial, not random, then you can try to account for them. Good luck.

Regards,

A. Hi, Darcy. Stirring is okay but it adds an additional variable, so I wouldn't do it. There might be faster rusting at the surface if the nails were partially submerged, but again it's another complicating variable. It depends on what you want to do.

I don't agree with or understand this distinction between "surface rust" and "permanent rust", although I agree that rusting can vary from minor to catastrophic.

Regards,

A. Hi, Emily. I'll bet your librarian can find age appropriate books or chapters of books in minutes. The principle is that hopefully you will be able to demonstrate that the amount of corrosion is related somehow to the salt concentration. So your hypothesis can be: "The more salt, the more corrosive water is to metal" or "The less salt, the more corrosive water is to metal". Good luck.

Regards,

A. The tap water (fresh water) has more effect than sea water.
Sea water will lead to "general corrosion" due to its good conductivity.

Fresh (tap) water will lead to (local corrosion) due to less conductivity

A. Hi, Cece.

Your wording may not be precise, but your finding is correct. Yes, applying electricity can greatly accelerate the corrosion. But rather than asking, you should make it your hypothesis that applying electricity increases corrosion, and then do some experiments demonstrating it. Low voltage batteries only (1-1/2 volt), because electricity plus water is very dangerous.

Regards,

Hi, Niralee.

Well, you have an experimental procedure established (the 3 metals you have selected and the 3 different solutions), but you have no hypothesis yet, and that's a bit backwards because the experimental procedure you propose is supposed to be designed to try to prove or disprove your hypothesis. To better understand the problem, suppose I told you I'm going to ride my bike around the block 3 times clockwise, then walk around the block 3 times counterclockwise -- and I then ask you what my hypothesis about that travel should be. It could be anything: that bike riding made me more dizzy? that walking took less time? that going clockwise resulted in fewer mosquito bites?

Here's one possible hypothesis for you: "Iron will corrode faster than copper or aluminum whether tested in tap water, salt water, or vinegar". Good luck. But, next time, you need the hypothesis first :-)

Regards,

A. Hi Braydee. What you can probably say is that distilled water causes steel to rust faster and more than salt water. You can pass the salt water remains though a coffee filter and see what color the water is then (clear, cloudy, rusty, or green) which will tell you whether the green color is some sort of precipitate or a soluble salt. I'm not sure that you can say anything further without more experiment, but proposing what the next experiment could be might get you extra credit.

Regards,

A. Hi Christopher. The idea of these science projects is to actually do them and to learn for yourself from doing it yourself rather than depending on conventional "book knowledge" -- which can be wrong. But don't be disappointed if you see no corrosion of the nickel in either saltwater or tap water without the time to complete your assignment.

You might learn, as one possibility: "Nickel is quite corrosion resistant and did not visibly corrode in either salt water or fresh water in the one week time frame of this experiment". Good luck.

Regards,

A. Hi Gaby. Yes, 3 weeks should be plenty of time. While wearing plastic gloves, you can use sandpaper to remove any tarnish or rust off of one side of your test items so you have a nice fresh clean non-corroded surface which should tarnish or rust very quickly.

Regards,