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Rusting Nails student experiment & research (cont'd)


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(2004)

Hi, I am doing a chemistry report on the effects of different soft drinks on rust, and which removes the rust quicker. I read in earlier responses that this is a pretty wishy washy experiment, or not very accurate, and was wondering if I was to also titrate to find both the carbonic and phosphoric acid concentrations in the soft drinks, if I would still be able to make links between the rate at which each soft drink de-rusted the nail, and their acid concentrations and pH? Or is this a futile idea and I should quickly find a new one?

Thanks heaps.

Pip B [last name deleted for privacy by Editor]
- Brisbane, Qld, Australia


(2004)

Hi!

Well I'm doing my science fair project right now. I'm doing it on which liquid can dissolve rust off of nails best. I'm doing that to discover a new cleaner to take off rust of vehicles, sinks, etc. And I am doing great with my project, but all I need is some research like if anybody has found any articles, if they have any facts, anything!

Thank - you!

P.S.: I luv 2 act! lol

Scarlett [last name deleted for privacy by Editor]
- Ontario, Canada


Hey!

I'm Scarlett's best friend and I agree with her letter! LOL! She is doing really well on her project and all of our friends love it but she is desperate for info! So if anyone knows anything about rust, oxidation,iron,nails,or metal, or anything to do with that, send a letter also and let her know! LoL, sincerely, Alison

P.S.: I luv 2 act 2!

Alison [last name deleted for privacy by Editor]
- Ontario, Canada


(2005)

Q. Hi Mr. Mooney,

My daughter and I need your help. She is submitting a science project titled How does electrolysis play a major role in the process of electroplating? My daughters experiment starts out with salt water in a bottle with a six volt battery. I have 2 wires, a penny is attached to the positive connection via the wire, and the other wire is connected to the negative connection with a paper clip attached to it. We tried doing this experiment with 2 D batteries and nothing happened, we then went with the 6 volt battery instead. My Question to you is why is the penny black and the paper clip black? What caused this discoloration to occur. After my daughter did the penny and the paper clip, we then did a penny and nickel to see what would happen. We taped the penny to the positive pole of the battery and the nickel to then negative pole. In about 15 mins the nickel was black and so was the penny. what happened. In the experiment they stated it should turn bluish-greenish. This did not occur and I can not find out from any resource why they are both black. Please help to explain this occurrence, as we are running out of time for her to present her experiment. Any help would be very much appreciated. Thank You so much.

Margaret S [last name deleted for privacy by Editor]
science project - Chicago, Illinois


(2005)

A. Don't "run out of time" on my account, folks :-)

There are hundreds of different student projects, and tens of thousands of students with each. I don't want to blow people off, but if I did nothing else 24/7 I could not begin to answer all the student questions that are submitted! So please consider these pages to be like Dear Abby or Hints from Heloise column where we post interesting letters, and if no student answers it, we may occasionally compose a response ourselves.

Margaret: your electrolysis experiment doesn't seem to really have much to do with electroplating, as you'll understand in a minute...

What happens in electroplating is that metals are dissolved (oxidized) into solution as positively charged ions at the positive pole (anode) as current is applied, and they are attracted to and migrate to the negative pole (cathode) where negative charges (electrons) neutralize them and "reduce" them back to metallic form. This is explained in our FAQ on the subject.

In order for electroplating to occur then, the metal must dissolve into solution at the anode and stay dissolved until those metal ions migrate to the cathode for reduction back to metal. But plain salt water (without acid or exotic chelating/complexing agents) cannot dissolve metal, it cannot keep metal in solution, so with no metal ions dissolved in solution, you can't electroplate any out -- electroplating cannot occur.

With no metal in solution, all that the electricity can do (and it does do) is separate the H2O water molecules into hydrogen gas and oxygen gas. The excess electrons available at the cathode convert hydrogen ions in the water into hydrogen gas while the electrons pulled away from oxygen ions at the anode convert them to oxygen gas.

The black color that is on everything is what platers call 'smut' and it is largely comprised of very very fine particles. When particles are very fine, they appear black regardless of their natural color because the light hitting them doesn't bounce back towards the source but bounces off at a skew angle and gets diffused and absorbed. The particles may be metal precipitates caused by the attempt of the electricity to dissolve the metal at the anode but the salt water not keeping it in solution but letting it form tiny metal oxide particles instead.

2 D-cells, i.e. 3 volts, is plenty for electroplating for a science experiment. One D-cell, i.e., 1-1/2 volts is usually enough really. Six volts is too much and will cause smut even if you had vinegar or another acid in the solution.

The nickel should have been connected to the positive pole if you want it to ionize to a green color because things dissolve at the positive pole, not the negative pole. But I'm not confident you will get green rather than black anyway--you might possibly if things go well. If you want to try electroplating, the conditions described in the previously mentioned FAQ will work, I've done it.

I know it's very confusing and a lot to learn, but good luck to you and your daughter.

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


(for Kindle)
Unforgettable Experiments
that make Science Fun

(2005)

Excuse me if this looks like I've just copied and pasted the question.... but I have.

I need to research the chemistry of rusting and describe what is happening in terms of redox reactions. as well as include an explanation of E values and balanced redox equations.

I also need to research the hydrogen-oxygen fuel cell and describe what is happening in terms of redox reactions and include an explanation of E values and balanced redox equations.

Please can you give me some starters eg: where to look, what the question means, etc etc.

Thanks guys, and good luck.

James L [last name deleted for privacy by Editor]
student - Bolton, England, United Kingdom


(2005)

Well one thing is base liquids rust the nails slow and neutral medium and acid FAST! I really think that before you test make predictions.

Andrew Xu
- Chicago Illinois


(2006)

Hello,

To all of you to whom this can help here's what I know.
I know that Dr. Pepper will not rust a nail I am in 7th grade and I am doing a project on which substance will rust nails faster water,vinegar, Windex,or Dr.Pepper. It turned out that the water did the 1st most damage and the Windex did the 2nd most damage,the vinegar did the 3rd most damage and the Dr. Pepper did the least damage. So if any needs to know any of this here it is and I have a question it why do all of you even want to know all of this ?

Jessica Nicole B [last name deleted for privacy by Editor]
- La Veta, Colorado


Earth Science for Every Kid

(2006)

Hi, I am in grade 7 and:

I am doing a science project on rust. My project is to determine the effects of different liquids on iron nails, specifically which liquids cause rust to happen most quickly. I used 4 iron nails, 4 canning jars with lids, 4 liquids - sea water, tap water, sugar water (1 tsp in about 8 oz of water) and bleach. A nail was put into each jar and then one of the 4 liquids was used to fill the jar and completely cover the nail. After 48 hours I saw the following:

nail in tap water - lots of rust, rust was very clumpy, clumpy rust residue was on the bottom of the jar and water was bit cloudy, but not much

nail in salt water - nail completely covered in a dusting of rust (rust not clumpy at all but looked like dust), water was very cloudy and lots of rust dust sat on the bottom of the jar and about 1/4 way up the sides of the jar


nail in sugar water: results very much like the tap water results but not as much rust - but rust was clumpy

nail in bleach: not much rust at all, very very little and no rust in the liquid or at bottom of the jar - the funny thing is the rust was very dark, black, compared to the orange/brown colour of the rust in the other liquids

my questions:
why is some rust clumpy (tap, sugar water) versus dusty (sea water)
why is the rust in the bleach black instead of orange/brown in colour
why is the nail in tap water rusting the quickest when compared to sugar water

thank you for your help

Mitchell M [last name deleted for privacy by Editor]
gr 7 student, Irwin Park Elementary - West Vancouver, B.C., Canada


(2006)

Q. My daughter is in second grade and we have run a ten day experiment on different metals (copper, stainless steel, steel and aluminum) in distilled H2O, salt H2O and rain H2O. We have documented when the rust appears in each solution (or does not appear with the non rusting nails). My question is...how can we document the amount of rust on each nail. We do not have access to a precise scale and would like to do something more scientific that yes there's rust or no there is not rust. Any ideas?
Thanks,.

Kerry C [last name deleted for privacy by Editor]
- Pleasant Garden, North Carolina


(2006)

A. Just the question may be beyond 2nd grade level, Kerry :-)

I'd suggest wiping the rust off the nail onto a Mr. Coffee filter, and pouring the solution through the same filter. When it dries she can tape the rusty area of the coffee filters to her project board as a good qualitative measure of rust.

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


Kids Guide to Research

(2006)

Q. I am a 6th grader doing a science project on "Which kind of water will rust a nail faster, salt water or tap water?" Well I found out my variables: the independent variable is whichever kind of water I used for each of my experiments, and my constants are the amount of water, the nails, and the glass containers, and my dependent variable is the [amount of rust on the] nails. My hypothesis is excellent. When I did my experiment(s) at 7:50 PM I woke up the next morning at 6:22 and the tap water had already rusted why is that? When I looked it up on the internet it says that the salt water was going to rust faster then I did a little bit of research at the library and I found out that it would take the salt water a little while to rust because the salt preserves the nails. I even came on here and tried to find some answers PLEASE IF You HAVE A SCIENCE FAIR PROJECT LOOK AT THIS BECAUSE IT WILL HELP YOU!

Angela B [last name deleted for privacy by Editor]
- Smithfield, North Carolina


(2006)

A. I finally ran this experiment myself, Angela, and feel that a student will NOT see any reliable difference in the rust rate for fresh and salt water as the experiment was described to me. See letter 38861 for my results. Good luck.

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


(2006)

Q. Well to the finishing. com people (not to be rude cause I don't know your name) what kind of nails did you use? I used wire nails and in my classroom there is another group that did the same project that I did and their hypothesis came out the same as mine so I believe that you did something wrong. Did you do two experiments?

Angela B [last name deleted for privacy by Editor]
- Smithfield, North Carolina


Pop Bottle Science

(2006)

A. My response on letter 38861 describes the nails I used, Angela. The phrase "came out", in the sense you used it, doesn't apply to a hypothesis. A hypothesis is the theory you want to prove or disprove. The results of a properly conducted experiment tend to prove or disprove a hypothesis.

You said your hypothesis was excellent but you didn't say what your hypothesis was. Nonetheless, if three experiments were performed and two leaned your way and one leaned the other way, then there is more evidence to support your hypothesis than there is to refute the hypothesis, but there is not so much evidence to support the hypothesis that you should become overconfident. Good luck.

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


(2006)

I'm conducting an experiment on nails and rust, I've placed several nails in different solutions containing boiled water, tap and pond, each category has three containers in those container I added yeast, soil and nothing separately. I am taking into account the temperature of these containers, the setting(sun exposure)and pH level. All these are in sealed containers. I was wondering with all the information should I be keeping track of bacteria growth and if so how should I be doing it, I've heard a lot about agar petri dishes, are those recommended.
I am a grade eleven student, and would be very appreciative for your help!

Kate Z [last name deleted for privacy by Editor]
experiment - Halifax, Nova Scotia, Canada


(2006)

Q. Hi, I'm in Grade 11 in Australia and I'm also (like every other student in the world) doing an experiment on rusting nails.
I'm having a hard time finding chemical equations, and I was wondering if anyone could give me some pointers on the equations for a nail in bleach (links or books would be fine)
Thanks

Christine L [last name deleted for privacy by Editor]
- Canberra, ACT Australia


Award Winning Science Fair Projects

(2006)

A. I can give you a start, Christine, by telling you that bleach is about 10% NaOCl dissolved in water with NaOH added to keep the pH high so that it does not spontaneously degenerate and release excessive Cl2. NaOCl is named 'sodium hypochlorite'. Maybe by hunting for the formula or chemical name you will find how it reacts with Fe.

But it is a powerful oxidizing agent, which is why it will bleach dyes and why it disinfects. It would seem to me, although I haven't researched it, that iron plus an oxidizing agent should give you oxidized iron, i.e., rust. Mitchell reported that bleach caused little rust, but very dark rust.

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


(2006)

Q. I am doing a Science fair project on which household product will protect a nail from rusting the longest. I am using cooking oil spray, Vaseline, motor oil and anti-freeze. I will weigh the nails before I place them in water and then every 24 hours. The question I have is, will the nail weigh more or less when rust starts to form?

Jarrett M [last name deleted for privacy by Editor]
student - Allentown, Pennsylvania


(2006)

A. Well, the rust is the original iron plus oxygen, so the nail plus the rust will theoretically weigh more than the nail. But rust is non-adherent; some will be on the nail but some will sludge off into the solution. So the way to do it is to rub the rust off and weigh the now rust-free nail -- which will weigh less than it originally did.

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


(2007)

Q. Hi. I am a 6th grader who can't find any research for the subject "How does a more neutral pH scaled effect the rust growth on iron nails". If anyone has any answer or website for this they can respond here. Thank you for reading this and I hope you have some information on weather you can help me. This is also a science fair project so if you help me I would recognize this website and include your name in my project so please...HELP ME!

Signed,
Clueless and Confused

P.S....I'm a girl boys so please help me out!

Shanna [last name deleted for privacy by Editor]
school - Edina, Minnesota


(2007)

A. The purpose of your project isn't really for you to break new ground and produce new advances in corrosion science . . . the purpose of your report is for you to learn how to proceed on such research projects, Shanna. This is what libraries are for. The way to proceed is to start at the library, with a librarian giving you general guidance on how to start researching (not to ask someone to do your homework for you because you're a girl). Boys should carry your books, yes (I'm old fashioned). But do your homework? No :-)

If you have a specific question or problem area after the project is underway, we'll try to help.

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


(2007)

Q. I'm in 8th grade and my teacher told us that Coca Cola can make a penny dissolve. I was wondering how long do you think it would take? I'm going to conduct my own experiment and see which type of cola (diet, regular, with lime, C0, etc.) will work faster. I would like to work within a week so I need to know if it will last longer than that.
=)

Zoe [last name deleted for privacy by Editor]
student - NYC, New York


(2007)

A. First, make sure that all of your pennies are 1983 or later, Zoe, so that they will be made of a zinc core with copper plating. Pennies before 1982 were solid copper and will not dissolve in Coke. If this is not in your lab notes please tell your teacher to put it in for future students.

Second, fold some of your pennies in half with pliers or a vise to expose the zinc, or cut them into pie pieces with tin snips so the Coke can get to it easily, instead of having to find it's way through microscopically small holes in the copper plating. Now they should corrode very substantially within a week.

Third ask your teacher, before you start, what lesson you are supposed to learn from this. Darwin himself said that one of the worst pities would be to spend your life going down to a gravel pit every day and categorizing each pebble by weight and color. So pointless! So what is the point in finding that one secret formula such as regular or with lime, corrodes a penny faster than some other secret formula. Coca-Cola could change the formulations any day they wish, even right in the middle of your experiments.

So perhaps the actual answer you get is pointless and the real purpose of your work is to learn experimental procedure. And here's the most important thing you will learn from the experiment: buy a small bound notebook (composition book), number the pages, and write down every step you do and everything you see, everything, don't rely on your memory of any of it -- have the notebook open and the pen uncapped every second you are working on it.

The first paragraph will probably be that you used only post 1982 pennies because . . .

The second paragraph will probably be that you folded them in half because . . .

Submitting that notebook should get you an A+.

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


November 25, 2008

My son is in third grade and we are about to begin an experiment to see if Coke, spring water or nail polish will remove rust better.

Before we start I wanted to see if I could get some suggestions of what he needs to take measurements of. I think he has to have 2 graphs.

He is aware that he needs to check the color of the nail and water as well as check the weight of the nail because we have done that in past experiments. Should we check the pH of the liquid as well?

Does rust have a higher pH and is it more acidic or is considered a base? We will go to the library to back up findings.

Thanks for your help. My son loves science projects!

Janine B [last name deleted for privacy by Editor]
mother of student - League City, Texas


sidebar January 7, 2009

Mr. Mooney & the other adults that are suggesting these kids are not doing their own experiments need to understand that, although in some cases they may be correct, some of these kids are required to do a research paper as well as an experiment. I am working with my 8 year old on his required assignment, and finding information about how different liquids affect the rusting process is not an easy thing. It should be up to their parents to decide how much of this the kids are doing properly & how much is taking the easy way out. Kathy Masters
- Humble, Texas


Hi, Kathy. Of course it is up to their parents to decide; I wouldn't dream of suggesting otherwise!

But when a student posts a question, we often don't know if they are a 2nd grader or a high school Senior, and they usually give us no clue to the degree of parental involvement. If I am asked to answer a question that may be from a high schooler, that makes me feel like an enabler towards damaging the child's science learning, it is my right to decline.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


January 3, 2009

Q. i have this project and haven't been able to find the information I'm looking for so can you tell me what causes a steel nail to rust more ammonia or water and why. thank you so much.

arianna c [last name deleted for privacy by Editor]
student - guyana


"Hands-on" learning is fun, maybe try a precision scale? . . .

Electronic scale

January 10, 2009

A. Hi, Arianna. Conduct an experiment based on the clues on this page, tell us the results you got, and I'll try to help you explain it.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


January 4, 2009

Q. okay well me and my sister are doing a science project on rusting nails we are in the 8th grade...this is the back up info... we are rusting steel nails one will be hanging above either tap water, coke, vinegar,and orange juice. we will put one nail above a plastic container and one inside the same one the other nail is hanging from. we need help because we are kinda doing this project late and well we have to write an introduction I just need some help to find some research on this topic and a little guidance on this project as well

thank you

anna and brenda p [last name deleted for privacy by Editor]
student - san antonio Texas


January 10, 2009

A. Hi, Anna & Brenda. Your librarian can point you to age-appropriate books on corrosion; but if your teacher trusts internet sources, most of what you need is in this one thread, and everything you need can be found by searching this site for "student rust".

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


September 4, 2009

I'm in 8th grade and I have to do a project for science fair and I'm testing if a steel nail will rust faster in pond water, tap water, or salt water. I can't find info so I can make a hypothesis of which will rust faster and slower I also need help on how I should conduct this experiment and how much time they need to sit in the different water and how much salt I need to put in the salt water. HELP!

Lucy H [last name deleted for privacy by Editor]
- Wichita, Kansas


October 26, 2009

I'm in the 8th grade, I'm doing a project to see what liquids rust nails the fastest. I understand the procedure and everything but I need to get some ideas for liquid. I know I have to start with a control (tap water), but I need other liquids. Could you please help!

Nick B [last name deleted for privacy by Editor]
student - Fort Walton Beach, Florida, United States


October 26, 2009

Hi, Nick. People on this page have already suggested salt water, pickle juice, vinegar, rubbing alcohol, Dr. Pepper, bleach, oil, sugar water, cold boiled water, Coke, Sprite, Diet Coke, Seven Up, Lemonade, and Windex. That sounds like a good list to pick from, but:
1. Be sure not to add any other liquids to the bleach or Windex as that can be dangerous.
2. I'd prefer avoiding the sodas, only because they are secret formulas that can change; if you don't know what is in them, it's hard to make genuine and useful scientific observations. And if they make changes, then what was true yesterday may not be true tomorrow.

Good luck.

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


May 1, 2010

i have a science fair in two weeks so I was wandering if you could tell me how does rust form, where does it form best and how long it takes for rust to form? if you could tell me soon I would really appreciate it. p.s I was going to do my science project on a nail. I'm in a fourth grade class and I am 10 yrs. old. THANKS FOR LISTENING TO ME AND THANKS FOR YOUR SUPPORT~!

katie m [last name deleted for privacy by Editor]
- exeter, Nebraska, us of a


June 29, 2010

Hi, My name is chelsea and I'm in the 11th grade. I am doing an experiment on the effects of different contaminants in the rate of rusting iron nails, I just wanted to ask about the procedure. Do you leave the nails in the solution for 2 weeks straight?, or do you have to let it out every night?. Do you also have to clean the nails afterwards?
I really need your help...Thank you!

Chelsea C [last name deleted for privacy by Editor]
- Laguna, Philippines


June 29, 2010

Hi, Chelsea. I would have expected your teacher to give you the procedures s/he wanted followed. But if not, then you get to choose your own.

I would leave the nails in the solution since it's simpler and easier to retain consistency.

The way a professional would do this is to start by weighing the nails before the test. After the test, any accumulated rust would be removed, then the nail would be weighed again to see how much weight loss it suffered. So, as for cleaning the nails after the test, it depends on how you are going to try to quantify the amount of rust.

Good luck.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


June 29, 2010

Hi, It's me again. I'm about to start my experiment but I wanted to know if the contaminants I chose is good enough. So far I have chosen salt water, water with sugar, vinegar, lemon juice, and pepsi cola. Are those good enough? or do I have to change any of them?
Please help...Thank you!

Chelsea C [last name deleted for privacy by Editor]
- Laguna, Philippines


July 2010

Hi, Chelsea. They sound like good choices to me. Good luck.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


July 7, 2010

Hi, It's me...again...I have reviewed my results and so far:
the nail in salt water rusted the fastest,
the nail in the vinegar turned black, and
the nail in the orange juice turned black as well.

I was wondering why? why did the one in saltwater rust the fastest, the vinegar and the orange juice turned black? And I was wondering how to graph the results...do I weigh them again...or do I just measure the height of the rust in the nail? which is more accurate?

Please I really need your help. And thank you very very much for all the help you have done in my project. I will surely put you on my acknowledgment. Thanks again..God bless!

Chelsea C [last name deleted for privacy by Editor]
- Laguna, Philippines


July 7, 2010

Hi, Chelsea. Although this has been explained a dozen times on other threads on this site, it is probably hard to find, so I'll bore some readers by repeating the explanation here :-)

Students (and some teachers) assume that rust is the best indication that corrosion is occurring, but it isn't! In fact, in industry, acids are used not to create rust but to remove it. Although acids can dissolve metal, they will dissolve rust faster, leaving the surface rust-free.

So what has happened is --

With your vinegar and orange juice, any rust has been dissolved into the acid. In addition, a very small amount of iron has probably also been dissolved. Steel nails are made of iron plus a small amount of carbon. As the iron dissolved, it left behind the very tiny specs of carbon because carbon is not soluble in mild acids. You will probably find out that this black "smut" can be wiped off with a tissue or paper towel. But I'd suggest wiping it off onto a coffee filter instead, so all of your corrosion products are "mounted" on coffee filters.

In the salt water, the iron from the nails combined with oxygen dissolved in the water to form iron oxide (rust). I'd suggest rubbing any rust off onto a coffee filter and pouring the liquid through the coffee filter.

The amount of rust and smut on the coffee filters should be a good measure of what happened. The ideal way to measure corrosion is by the reduction of weight of the nail between start and finish, but I doubt that you have scales of sufficient accuracy, so you may have to exhibit your coffee filters as your measurements. You can do a rough graph of how much smut and rust you see on each coffee filter. Good luck.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


July 8, 2010

Hi, it's me again. I am almost finished with my written report but I still don't have a hypothesis...I'm sure you're not allowed to give a hypothesis to me, but I was wondering if the hypotheses I chose is correct. My hypothesis is that the nail in the salt water will rust the fastest. I'm a little bit confused. My topic is the effects of different contaminants on the rate of rusting. So I don't think my hypotheses is right for my chosen topic. What do you think?

Please help me...I really really need your help...
Thank very much....

Chelsea C. [last name deleted for privacy by Editor]
- Laguna, Philippines


July 8, 2010

I can't be anybody's tutor or personal advisor, Chelsea, and this is my 4th response to you -- but hopefully this dialog will be helpful to other students.

Let's take it from the top --

You don't just start an experiment with no purpose. As I noted in my response to Zoe in about the middle of this thread, Darwin himself said that this would be like going into a gravel pit every day and pointlessly writing down the size and color of each piece of gravel. There needs to be a point to your experiment, something that you are trying to prove or disprove. That "something" is your hypothesis.

The "hypothesis" that you now suggest might have been okay, but you were supposed to form your hypothesis before you began your experiment, and the purpose of the experiment was to see whether the evidence supported or tended to refute your hypothesis. The position you are in now is that you want to use your "conclusion" that salt water rusts things fastest as your hypothesis. See the problem, and why that's no good?

So let's look at it this way: when you began your experiment, you suspected that different contaminants would affect the rusting rate. You didn't know it to be a fact, you just suspected it based on intuition, previous experience, or rumors you heard, etc., right? What you wanted to do was to conduct an experiment to support or refute that suspicion. So, how about this as your hypothesis: "When nails are immersed in water-based liquids, the amount of rust that is formed will vary depending upon what contaminants are in the water they are immersed in."

So you picked a good variety of liquids (salt water, sugar water, vinegar, orange juice, and Dr. Pepper) and ran an experiment to prove this hypothesis -- and the conclusion was pretty clear: the amount of visible rust on the nails in salt water was the greatest. You also discovered that immersion in vinegar or orange juice produced a black smut on the nails. You believe that this black smut is carbon that did not dissolve in these mild acids, but you do not know that for a fact, so you suggest a good hypothesis for next year's science experiment might be: "Immersing nails in vinegar or orange juice dissolves some iron from their surface, leaving behind a carbon smut".

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


July 12, 2010

Good day, My name is Naomi and I was assigned a rusting rate project. We also had to write a written report but I don't have a problems or specific questions to answer in my project. So far, my problems are: Which of the contaminants have the most significant effect on the rate of rusting iron nails?
Which nail rusts the fastest?
What properties are present in the contaminants that may have an effect on the nails?
Are those related or acceptable in my topic? My topic is the effects of salt and other contaminants on rate rusting?
Please I really need your help.... thank you!

Naomi F [last name deleted for privacy by Editor]
- Los Angeles, California


July 12, 2010

Hi, Naomi. Are you in 2nd grade and this is your first-ever science project, or are you a senior in high school, with a wealth of such projects behind you, and ready to start your career or head off to a university?

Not trying to give you a hard time, but please understand that you're expected to learn an awful lot in the nine or ten intervening years, so a senior project bears little resemblance to a 2nd grade project and nobody can help you plan a project until they have some sense of how deep your knowledge of chemistry is supposed to be at this point.

Regards,

Ted Mooney, finishing.com
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Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


July 19, 2010

Hello....
I'm in the 9th grade and I have a question abt my project which is the effects of different contaminants on the rate of rusting. On the previous answers you have given, you said that you can measure the rust by rubbing the rust off the nail. How do you measure the rust that was rubbed? And as you answered in Chelsea's question, you stated that the black smut that was found in the nail in the vinegar are carbon specs left behind. I wanted to ask if it was still considered as rust?. Because that also happened in my project.
PLEASE PLEASE HELP ME! I DESPERATELY NEED YOUR HELP...THANKS!

Ella C [last name deleted for privacy by Editor]
- Makati, Philippines


July 19, 2010

Hi, Ella. If you desperately need help, I feel you are probably not properly interfacing with your teacher because it is certainly not your teacher's intent to force you to look for help from strangers on the internet :-)

The ideal way to measure rust is to weigh the nail before you start the experiment, let it rust in the solution for your experiment, then use special chemicals to dissolve away the rust, and then weigh the nail again -- determining the amount of corrosion by how much weight the nail has lost.

But depending on what grade you are in, what chemicals the school lets you use, and what equipment your school has, you may have to compromise rather than doing it the ideal way. A compromise which is probably suitable for younger grades is to rub off any rust you can onto a coffee filter, and pour the rusty water through the same filter.  You can't actually "measure" rust this way, but I think you can "judge" the relative amount of rusting by looking at how much rust is on the filter.

I am only guessing that the black smut is carbon specs; neither of us has done an experiment that proves it. But, no, carbon is not rust. "Rust" is iron oxide, the chemical combination of iron from the nail with oxygen from the air or dissolved in the liquid.

I believe the right approach to your report is to understand the principles that we've talked about here, and describe what you've found and the limitations on what you've been able to do. Good luck.

Regards,

Ted Mooney, finishing.com
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Ted Mooney, P.E. RET
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Pine Beach, New Jersey


July 21, 2010

HELP! Based on other studies in this site, the nail that was immersed in vinegar turned black...mine didn't! It was black for the tenth day but since my experiment was for 14 days I didn't take a picture of it.... When the fourteenth day arrived the said nail was black and the one in the salt water had less rust.... what happened to my project? By the way I'm an eleventh grader and my project is the effects of different contaminants on the rusting rate on nails..
Please Help me....I desperately need it!
Thank you!

Casey R [last name deleted for privacy by Editor]
- Lockport, Illinois


July 28, 2010

Hi, Casey. I can't even understand what you are trying to relate -- you have said you expected it to be black and it was, both on the 10th day and the 14th, but it seems that what you said isn't what you mean. So I think the most important thing you need to do is work on a careful description of exactly what you did and exactly what you saw. The methodology of your project and report is far more important than getting the "right" answer. Explain what happened very carefully, then advance a theory that would explain it, and research whether the theory makes sense. Good luck.

Regards,

Ted Mooney, finishing.com
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Ted Mooney, P.E. RET
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Pine Beach, New Jersey

July 29, 2010

Hello, What I meant with the question was that in my experiment, the nail that was in the vinegar rusted the most, while in most of the research that I saw salt was supposed to rust more. I followed the procedure that was to weigh the nails before and after the experiment. But before I weighed the nails after the experiment, I cleaned the rust off to see how much weight is lost. In my project, It showed that vinegar had the most weight loss, while salt had the least weight loss. I just wanted to ask why it happened? Why was vinegar the nail that had the most rust?

I really really really need your help. This project is due next week and I still don't know why the results happened. Please Please help me.....Thanks....

Casey R [last name deleted for privacy by Editor]
- Lockport, Illinois


July 29, 2010

Hi,Casey. I know you don't quite believe me, but you continue to not carefully define for yourself what the words you are using mean. I can see you tossing the word "rust" around in an inconsistent fashion: meaning visible rust one moment, total dissolved iron the next time, amount of weight loss the third time, and back and forth. Until the word has a fixed and stable meaning to you, you will continue to run around in circles of confusion.

Of the solutions that you are using, vinegar is the most corrosive. That is because it is an acid, and acids directly dissolve iron into solution. But as mentioned several times on this thread already, acids are more commonly used to dissolve rust than to create rust; that is because they will dissolve rust faster than they will dissolve metal, leaving a rust-free surface.

Here is what may be happening. The vinegar initially dissolved any small amount of rust that was on the nail, then it began to slowly dissolve the iron itself (as proven by your weight loss measurement). So now the vinegar/water solution has iron dissolved into it. The acetic acid of the vinegar, over time, leaves the solution as a fume or vapor (that's why you smell it). At the same time, the water is also evaporating. At some point, as the acid and water go missing, and the iron that was dissolved remains behind, it can't stay in solution because it's too concentrated for the remaining acid and water to keep dissolved. This should not be a surprise, sweat is salt water and it leaves salt stains behind as it evaporates too. The dissolved iron reacts with the air and water and forms rust. Since vinegar dissolves the most metal (iron), the residue will have the most iron, and when that residue eventually dries and converts to rust, there will be more of it.

Again, sticking with consistent meanings for words: nobody said salt water is more corrosive than vinegar; it isn't. What they said was salt water will produce visible rust whereas vinegar, at least initially, does not create rust but dissolves it instead; but when it's capacity for holding the metal in solution dissipates, the metal is left behind as rust.

Regards,

Ted Mooney, finishing.com
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Ted Mooney, P.E. RET
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Pine Beach, New Jersey


August 5, 2010

Please help me.... I'm a ninth grader and I did a rusting project. The effects of different contaminants on the rate of rusting. The contaminants that I chose were OJ, vinegar, and salt water. The nail in the vinegar rusted the most followed by orange juice, and then salt water. I know that the vinegar is acetic acid and dissolves metal and corrodes only when it is evaporated. But I wanted to ask about salt water. why did it rusted the least? Is it bec. it has a higher pH level? Or does it have something to do with electrochem?

Please help me...need a response by hpoefully tom....thank you so much....

Erika R. [last name deleted for privacy by Editor]
- Los Angeles, California


October 5, 2010

Q. Hey ted I'm kim and um I'm doing a science project on the effects of soda on nails and I'm using dr. pepper, coke, vanilla coke, cherry coke, water, pepsi, and sprite now I've been told that nothing will dissolve keratin nor steel nails but what are your thoughts? and also I have to do note cards with this experiment how would I get A LOT of info that can fill 50 note cards? sincerely,
Kimberly Grace

Kimberly Grace E [last name deleted for privacy by Editor]
science I guess - Florida, U.S.

October 5, 2010

A. Hi, Kim.

50 note cards?! Does your teacher prefer Edward Everett's style to Abe Lincoln's? :-)

If I had my choice I would not use 6 different brands of soda, all of which probably rust stuff similarly (because they have the same basic ingredients of water, sugar, and phosphoric acid). The ingredient lists are secret, so if there are any differences in corrosiveness you'll never know why.

There would be little of extensible value that you can learn from such an experiment. So what is "extensible value"? Can you add 201 plus 103 right in your head right on the spot? Sure you can. Even though your teacher never taught you to add those two specific numbers together, you can add them because your teacher did show you the "extensible" method of adding the units column, then the tens column, then the hundreds column. But if you find that soda A is more corrosive than soda B, so what -- what else does it tell you or teach you? Nothing.

So please try to redesign your experiment with questions like: does the temperature matter, does more sugar increase the rusting or slow it down or have no effect, does the concentration of salt matter, does the concentration of acid matter (for example, straight vinegar vs. 50:50 vinegar to water). Try to find some property or aspect of your test solution that is measurable in some way, and see whether varying that property or aspect affects the rusting. Good luck.

Regards,

Ted Mooney, finishing.com
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Ted Mooney, P.E. RET
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Pine Beach, New Jersey


October 19, 2010

Q. Hello I am in 6th grade and I am doing a science fair project on "science What liquid will make a nail rust the fastest?" my materials are: vinegar,tap water,sprite. But I need an idea for the Procedure....
Write me back as soon as you can thanks!

Marie p [last name deleted for privacy by Editor]
science fair - New york

October 21, 2010

A. Hi, Marie.The answers are already on this thread repeatedly. Please ask your parents to review your understanding the word "procedure" and help you find the procedures that are described on this page. Good luck.

Regards,

Ted Mooney, finishing.com
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Ted Mooney, P.E. RET
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December 10, 2010

Q. I am a 7th grader and I need to know what the chemical reaction would be when vinegar rusts a nail. I saw the black stuff on it and want to know what it is.

Alisha V [last name deleted for privacy by Editor]
- Plano.Texas

December 12, 2010

A. Hi, Alisha. This is pretty advanced for a 7th-grader, but the chemical formula for vinegar (acetic acid) is Vinegar is HC2H3O2, and it will ionize to H+ + C2H3O2-. The chemical formula for an iron or steel nail is basically Fe.

The reaction is approximately Fe0 + 2H+C2H3O2- ==> Fe++(C2H3O2-)2 + H2^.

The iron goes into solution as ferrous acetate, and bubbles of hydrogen gas are released to the atmosphere.

Regards,

Ted Mooney, finishing.com
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Ted Mooney, P.E. RET
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February 10, 2011

Q. I have a 10 year old 4th grader that is doing a science fair project and I was never good at science and do not have all the answers to help him. I have read some of the threads and it helped me understand some to help my son understand his project, but I am left with other questions. He is doing a project on which of bleach, tap water (we have well water), or salt water would rust an uncoated framing nail the fastest. He has done the experiment twice now and has had very similar results. We found that the bleach rusted the most and quickest and I think I have gathered from some of the other threads on why as it basically has more oxygen released to cause the iron to oxidize more and quicker. I think I stated that correctly. Anyway, the tap water seemed to rust a bit more than the salt water in both of the experiments. I saw that you have done this experiment yourself and came to the conclusion that they rust about the same. My question would be why would in my sons experiments the tap water rust more than the salt water both times. He needs a reason to place with his graph he places on his poster board for the project and I have no idea on where to begin to look for an answer. My son is a straight A student which he gets from his father. lol He wants to excel and I am trying to help and I feel like someone is speaking a foreign language to me when it comes to science. My son suggested that the salt in the jar that the nail was half submerged in was preventing oxygen to be released and in turn caused less rust. I don't know if this is correct or not and don't want him looking silly with this conclusion if it's wrong. I just don't see what can be gained from this project besides him learning how to do one. He's been doing the journal and understands to get accurate results that an experiment must be done a few times to maintain the same results. But why would knowing that bleach rust something more be helpful? It's not like bridge building companies for example would have to worry about bleach getting on their bridge and corroding it.

Jackie Brown
- Boggstown, Indiana, USA

February 11, 2011

A. Hi, Jackie.

In the long term, in the real world, we know for certain that salt water is more corrosive than fresh water. This is known by every sailor, every engineer, and countless homeowners who have lived in both places; and it can be easily proven by well controlled accelerated corrosion tests. There are at least two reasons: first, chloride ions, as in sodium chloride salt, chemically attack metal and are corrosive to it; secondly, the dissolved salt increases the conductivity, allowing galvanic corrosion currents to flow easily.

But what can we say of short term tests by students? After dealing with reports of hundreds of tests here for many years, many reporting salt water to cause more rust, and many reporting fresh water to cause more rust, I ran the test myself and was unconvinced that there is any significant difference. If we then try to answer the question of WHY one is more corrosive than the other, we are confronted with the problem that the student actually has insufficient evidence to make such a claim in the first place because countless students got the opposite result :-(

One of our readers (Poppy Anne, letter 19024) claimed that the reason that fresh water is reported as more corrosive is that in the short term it is, but it builds a film of corrosion products on the nail that tend to slow further corrosion, whereas salt water penetrates this film and continues to corrode. I don't fully believe this, but it is one possible explanation. Perhaps another explanation is that as iron dissolves into these smallish dishes we quickly approach an equilibrium condition where the dissolved iron slows further dissolution, and the results would be entirely different in flowing water.

In short, I think your son should do the experiment as conclusively as he can, then try to advance an explanation, but introduce this information about the uncertainty of the results, because there are simply too many contrary results to dismiss them all based on testing two or three nails :-)

Your question about the significance of learning that bleach causes a lot of rust is a good one. But the internet is a giant one-room schoolhouse and while 4th graders don't know enough chemistry to learn an extensible lesson from this, high schoolers should. Another issue is that 4th graders can't use "real" chemicals for safety reasons (even high schoolers sometimes aren't allowed to these days, although for that age group I think it is shameful paranoia rather than a legitimate safety concern); this limits the cause-and-effect lessons they can learn. Your son is doing a very good experiment for a 4th grader though.

Regards,

Ted Mooney, finishing.com
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Ted Mooney, P.E. RET
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March 27, 2011

Q. Hey guys, I'm a grade ten student studying different pH's effects on nail corrosion.
We used HCl (aq) with a pH of 1.6, a mixture from our teacher of HCl (aq) and water with a pH of 4.3, and tap water with a pH of 6.
What we found was that the higher pHs produced what appeared more corrosion, but when we extracted them from the test tubes and removed their rust, the nail stayed the same weight! The lowest pH did however weigh the least, but there was very little rusting. I assume the acidic part of the HCl removed the rust, and I understand that, but I don't understand how the very "rusty" nails didn't change in weight!

Savannah K [last name deleted for privacy by Editor]
Student - Burlington Ontario Canada

March 2011

A. Hi, Savannah. Rust can be very fluffy stuff like cotton candy, occupying a lot of volume and calling attention to itself when there isn't much substance. Although the rust weighed something, it was probably little enough that it was beyond the resolution of your scales. You did good.

Regards,

Ted Mooney, finishing.com
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Ted Mooney, P.E. RET
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June 21, 2011

Q. I have an experiment project in school ... but I always forget to do it ... but I just wanna ask what happens to a nail placed in a glass jar without water and uncovered?
And what happens to to a nail placed in a glass jar with water and is covered? does the nail in the water or or the other forms rust on it's surface? please answer .. :)

cristea s [last name deleted for privacy by Editor]
student - philippines

 

Hi, Cristea. Sorry, but faking the project is not something I want to help you with :-)

Regards,

Ted Mooney, finishing.com
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Ted Mooney, P.E. RET
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Pine Beach, New Jersey


December 20, 2011 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Hi, my name is genesis and I'm in the 9th grade. I'm doing a project based on rusting. I did my experiment and found that after a day of being in salt water and distilled water, nails rust faster in distilled water. Can you please explain why this happened?

Genesis P [last name deleted for privacy by Editor]
- Boston, Massachusetts

December 21, 2011

A. Hi, Genesis. We appended your question to a thread than answers it. Please see my response of Feb. 11, 2011, wherein I say that an experiment with a couple of nails under somewhat uncontrolled conditions may not render a conclusive result. But stuff can only dissolve to an equilibrium point, and I suppose it is vaguely possible that something similar to the "common-ion effect" could mean that the sodium and chloride ions in the saltwater could slightly slow down the dissolution of the iron compared to purer distilled water which has nothing dissolved in it yet. Distilled water can be "hungry" to dissolve stuff. Please patiently google "hungry water" to learn more. Good luck!

Regards,

Ted Mooney, finishing.com
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Ted Mooney, P.E. RET
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Pine Beach, New Jersey


January 2, 2012

Q. I helped my daughter post the following observation/request in a different post, but I am doing so here again because the topic here seems closer to her project and questions. My daughter and I will appreciate all explanations from the chemical professionals.

My 11 year-old 5th grader is doing a project on which 'environment' will cause rust to form fastest. She has used 6 non-galvanized nails cleaned with rubbing alcohol and placed in 6 test tubes filled with NOTHING, RICE, TAP WATER, OIL, VINEGAR, and BLEACH, respectively.
After nearly 7 days of observations and data recording, we have seen some expected results and some puzzling occurrences. All tubes were left at avg room temp of 70F and avg humidity of 40%. The tube with NOTHING had no rust to show - as expected because it would take a long time to form. The tube with RICE also showed no rust - presumably because of the hygroscopic property of rice. The tube with regular TAP WATER did show rust on the nail and lots of rust particles settled to bottom. The nail in OIL showed no rust - presumably due to the oil creating a coating around it and preventing oxygen and moisture from contacting the nail's surface. The nail in VINEGAR gave us a puzzle: there was no rust on the nail which was submerged in vinegar, but the surface outside of it was covered with an extremely crusty, dark reddish-brown and black substance (i presume it is rust, but it didn't look like what we saw in tap water.) The nail in BLEACH caused amazing rust-like clumps to form within a few days.
We expected the rust in water, but the results in vinegar and bleach has me stumped. I don't have an explanation for my daughter as to why the submerged half of nail in vinegar is free of rust but the surface untouched by the acidic liquid is covered profusely with dark rust-like material. Nor do I know what to say about the profuse clumps of light brown rust in the tube with nail and bleach.
I have read other posts having similar results, but I am not clear as to the WHY of the results. PLEASE HELP ME UNDERSTAND.

Roshni PARKER
- Houston, Texas, USA


January 2, 2012

Hi, Roshni.

Okay, you understood the first 4 results but not the vinegar result or bleach result. You also seem to understand that rust is an iron oxide, which is the reaction product of iron plus oxygen.

Vinegar is dilute acetic acid. Acids, as you may have seen in Hollywood movies, dissolve metal. Acids also dissolve rust. So, as long as you have vinegar left in the solution, and it's not exhausted (i.e., the acid hasn't evaporated away, nor become fully saturated with dissolved metal), there will be no rust on the nail because the vinegar has dissolved it and is continuing to dissolve it. Were the vinegar to dry up, the dissolved iron would no longer be dissolved and would quickly react with oxygen from the air to form rust. That is basically what is happening to the part of the nail that is not in solution. The acid vapors dissolved some of the metal, but since that half of the nail isn't wet, the iron can't stay dissolved, but reacts with the oxygen in the air to form rust. At the end of the experiment, you may want to pour the contents onto a paper towel and let it dry to see how rusty the paper becomes.

The bleach situation is a little different. Bleach is sodium hypochlorite, NaOCl. Chemical reactions can be complex, and viewed from different perspectives, but one way to look at it is that there is an awful lot of O in NaOCl that wants to react with iron to form iron oxide (rust). If no iron were present, the decomposition from NaOCl to NaCl + O would proceed quite slowly, but if there is iron available, the decomposition proceeds very quickly with the available iron locking up the O as iron oxide,

NaOCl (bleach) + Fe (nail) => NaCl (salt water) + FeO (rust)

Typical red rust is actually Fe2O3, rather than FeO, and the rusts you form under water may be iron hydroxides rather than iron oxides, so the formula I gave you is somewhat simplified; but it should convey the idea in more than sufficient depth for 5th grade. Good luck.

Regards,

Ted Mooney, finishing.com
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Ted Mooney, P.E. RET
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January 17, 2012

Q. I am doing an experiment on how easily galvanised iron nails go rusty compared to ordinary iron nails?

Priya R. [last name deleted for privacy by Editor]
- Guyana

February 15, 2012

thumbs up signTo Mr Ted Mooney and everyone else who helped us get explanations related to my daughter's 5th grade science project on rust... THANK YOU FOR ALL YOUR HELP!

My daughter's work earned her a TOP 5 in her school's 5th grade classes.

Besides the gratification of earning such recognition, my daughter has also learned some things that I could never have explained to her if it were not for the generosity of the experts moderating this forum.

KEEP UP THE GREAT WORK!

Roshni PARKER
- Houston, Texas, USA


February 16, 2012

We appreciate the compliment, Roshni, and thank you for taking the time. But as I'm sure you know, your daughter earned a Top 5 because she put in the effort. Thanks again.

Regards,

Ted Mooney, finishing.com
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Ted Mooney, P.E. RET
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February 20, 2012

hey yall listen I need help so go down
keep goin
can yall help me. I need facts on corrosion of a nail in Coke, Sprite and Sunkist. I am using a steel nail.
keep goin
you have reached the end bye-bye' y'all want a cookie? ps. I'm in the 5th grade

Mary Z [last name deleted for privacy by Editor]
- Upper Marlboro, Maryland


May 14, 2013

Q. I am doing a science project on how does the acidity of a solution affects the rate of oxidation of an iron nail. I really need help on my procedures.

Sahra [last name deleted for privacy by Editor]
- United State of America


May 14, 2013

A. Hi Sahra. Since you want to know the effect of acidity of the solution, you need to know the acidity of the solution. Your teacher will either give you pH paper (litmus paper) to test the acidity, or will tell you the pH of various solutions, or will ask you to research it. That's step 1 in your procedure then: figuring out how you are going to know the acidity of the solutions.

Regards,

Ted Mooney, finishing.com
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Ted Mooney, P.E. RET
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October 29, 2014

Q. I am a 7th grader doing a project on rusting nails. I need to know what the variables are for rusting nails. If you find anything please let me know. Thanks.

Adrianna S [last name deleted for privacy by Editor]
- Raeford, North Carolina


November 2014

A. Hi Adrianna. If you look at Angela B's letter above, she describes the independent variable, the constants, and the dependent variable.

Our FAQ "What juice or liquid cleans pennies best?" explains those terms, and all the terms used in your project. Good luck.

Regards,

Ted Mooney, finishing.com
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Ted Mooney, P.E. RET
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Dependent vs. independent variables

February 10, 2015

I am a parent helping a 4th grade student with the rusting nails science fair project.

We need to list independent and dependent variables. I am just at my wit's end trying to understand the difference.

HELP!! And, how can I know the difference between the two? Can you share a possible resource to help me with this confusion?

Angela Jefferson
- Laurel, Maryland


February 2015

A. Hi Angela. If you go nice & slow and don't panic, it's actually very easy :-)

A variable is anything that is changing/changeable as opposed to being constant/fixed. And you already know what independent means and dependent means.

If you put the words together, an independent variable is something we choose to change or vary, and a dependent variable is something that changes as a result of that choice. In everyday life, you can choose how much to eat (independent variable); then how hungry you still are when you get up from the table is a dependent variable, and how much weight you gain or lose is another dependent variable, and how much the dinner cost might be another dependent variable. You can choose to buy a Prius or a Humvee or a Ferrari (independent variable); then the average gas mileage you get is a dependent variable, and how much the car payments will set you back is another dependent variable, and how likely you are to survive a 40-mph crash could be yet another dependent variable.

There might be a thousand dependent variables in theory, but you don't necessarily have to be interested in all of them. For example, in choosing a car, if safety & survivability is extremely important to you, you might not care about gas mileage or cost (or leg room or top speed or trunk capacity or other facts & figures).

When it comes to an experiment about rusting nails, independent variables you might choose include what the nail is made out of, or what coatings you put on the nails, or what solutions you expose the nails to, or what temperature the solutions are, or how long you leave the nails in the solutions. A 4th-grade student will probably only vary one thing, for example what juices to use as their solutions. Generally, the dependent variable that you will be interested in is how much rust you get.

There might be other dependent variables in theory but you might not care about them. For example, if you chose to use vinegar in one of the experiments, you'd have less vinegar left in the bottle (dependent variable) but it's probably not a variable that you care about, and doesn't impact the experiment your child wants to do. So THE dependent variable for your child is the amount of rust. Good luck.

Regards,

Ted Mooney, finishing.com
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Ted Mooney, P.E. RET
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February 13, 2015

thumbs up signTHANK YOU, so very much!!! The way you explained it, makes perfectly good sense.

This website rocks!!!!!!!

Angela Jefferson
- Laurel, Maryland



Does temperature affect the time it takes for iron to rust?

October 3, 2015

Q. Alright so I need to do a science project and I chose this. I will be using the following: 4 of the same type of metal (Iron), same container (size wise and brand), and finally same type of water(Tap Water). The first container will be filled with water to about 1 1/2 inches with the piece of iron centered. The same will be for the rest.

The locations for each container will be the following: First One: Sun Light, Second One: Outdoor Shade, Third One: Indoors on a table/counter top, Last One: Inside a refrigerator. I will be constantly measuring the temperature on a graph for about 3 - 4 weeks. I would like to know if this is an efficient way to do my project? If not how else could I do it?

Giancarlo F
Student - 6th Grade - Miami, Florida, United States


October 2015

A. Hi Giancarlo. Your experiment sounds fine to me but there are a couple of things to watch for. First, that the solution in one or more containers may evaporate; I think you should have a fill line on the containers and periodically top them up if they get down to the 3/4 mark or so; or even better might be to cover them (maybe your mom has four matching tupperware containers with lids). Second, you might say that you have attempted to limit the effect of sunlight, humidity, and other factors by covering the containers, and are making the as-yet unproven assumption that those factors have not influenced your results. Have fun.

Regards,

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December 22, 2015

chemistry pd lab
topic: corrosion race
problem: plan and design an experiment to see which nail would rust faster (ordinary iron nail or galvanised nail).

nikkita wilson
- georgetown, guyana, south america


December 2015

Hi Nikkita. Yes, that sounds like a good science question/experiment. But so far you have done nothing (that we can see) except to post your homework assignment :-)

Please tell us what you have planned, or ask questions about what you see on this page, or something, anything, that we can comment on. Thanks.

Regards,

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February 1, 2016

Q. What happens to an iron nail after three days in sugar water?

Melinda A [last name deleted for privacy by Editor]
- Boston, Massachusetts


March 2016

A. Hi Melinda. Please describe exactly what you see, maybe including pictures if possible, and we will try to explain it.

Regards,

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October 28, 2016

Q. I am doing a grade 8 experiment on rusting nails. I am using water based paint and oil based paint and placing them in test tubes with tap water. I know that the oil based is more effective in stopping corrosion... but why? Why does oil based paint prevent corrosion better than water based paint?
Thanks

JOE B [last name deleted for privacy by Editor]
- Florida, USA


October 2016

A. Hi Joe. Can you attach photos or your interpretation of the results?

While it is true that some oil-based paints are better at preventing corrosion than some latex water-based paints, I don't think the general hypothesis is necessarily true. Whichever paint is most free of tiny pinholes, thickest, and best adhering is probably most effective. Additionally, some paints are specifically designed to deter rust, and may have rust-preventative chemicals in them, whereas others may be intended primarily to be used on wood and would not include the rust preventative.

I would suggest documenting as carefully as possible any notes on the paint cans that may help explain the differences.

Now if you were comparing actual water paints that preschool children use to oil paint that professional artists use, the water paints are designed to wash away with water, so they offer no protection at all from water. Good luck!

Regards,

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Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey

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