liquids causing rust

[tammy blevins]

My daughter is working on a science experiment for her 4th grade science fair. She is experimenting which liquid will cause a nail to rust faster. Her liquids are: tap water, muddy water (which she just stirred dirt in tap water), sprite, and salt water (salt stirred in tap water). She had researched that salt water causes rusting quickly. We were surprised when the tap water is the liquid that has created rust first. We are wondering if we should use distilled water instead, and should we have dissolved the salt in hot water prior to placing nail? She wants to be able to explain why the liquid caused the nail to rust first and maybe make a diagram. We are also hoping she used the correct type of nails for this experiment. She used framing nails. She did not sand them prior to placing in liquid. She has time to change up her experiment if needed. We are not sure how to explain why the tap water caused rusting quickly in a scientific manner. Any suggestions? Thank you for your help!

[klhjbh62604]

Hello tammy blevins:

Thanks for coming to Science Buddies. I hope we can help you. I am attaching a website you may want to look over.
http://www.corrosion-doctors.org/Experi ... mistry.htm
I think your daughter is well on her way with her project. As in all experiments there are many things that can affect the outcome of an experiment. As long as you have used the same type of nail for all conditions you should be fine. If you are going to repeat the experiment, you may want to dissolve the salt in the water to create the salt water. However, I feel you can stick with the data that you have already obtained. Remember the point of experiments are to test a hypothesis. Just because you do not get the results you are expecting does not mean your data is wrong.

If you have any questions please respond to this thread.
Keep up the great work.
klhjbh62604

[deleted-97919]

Tammy,

If you do decide to use hot water to make the salt dissolve, remember to allow the water to cool before you use the nail again. You want all of your liquids at the same temperature to start with so that you aren't affecting the rates of oxidation.

Rebecca