rust experiment method

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Science At Play: Instant Rust

• Nick Villagra
• November 10, 2020

I’m sure this is something we have all experienced before- you go outside and find a tool or other metal item completely discolored. You may already know, this discoloration is called rust. We typically expect something to take weeks or months to rust, but today I am going to show you a way you can rust a nail in just seconds. Want to see how it works, and how you can try this at home? Watch the video below to learn more.

Materials to Collect

• An iron nail (Make sure it’s not galvanized)
• A plastic or glass container that is large enough to hold your nail & all of the liquid ingredients. *Do not use a metal container or it might rust too* 
• 8 teaspoons hydrogen peroxide (3%) (you can pick this up at any store where they sell first aid supplies)
• 1 teaspoon distilled white vinegar
• Safety glasses or goggles to protect your eyes
• A pair of gloves 

Try it Out! (with adult supervision)

**Before doing this experiment, it is very important that all participants are wearing personal protective equipment (PPE): a pair of safety glasses or goggles and waterproof gloves.  A pair of safety glasses or safety goggles is ALWAYS a good idea when working with liquids that could splash in your eyes. It is also a good idea to have a pair of gloves on hand because you don’t want to have prolonged skin contact once these chemicals are combined.** 

Once you’ve collected all of your materials and have your personal protective equipment on, it’s time to start the science!

Step 1: Measure out your ingredients using the amounts listed in the materials section. If you need more solution, make sure you use 8 parts hydrogen peroxide to 1 part distilled vinegar as you measure out what you need. Then carefully combine the vinegar and hydrogen peroxide in your bowl.

**Once these liquids are combined, be careful not to touch the mixture. Putting on a pair of gloves when working with this solution is a great way to keep your hands safe.**

Step 2: Add enough salt to the mixture to saturate the solution (the same way you would make really salty water). Mix the solution together, you can use the nail if it is long enough, or you can use a wooden skewer.  If you use the nail to stir, you may see a rust color and bubbles start to appear.

Step 3: Place your nail in the container. If you’re rusting more than one nail, choose a container large enough to hold all of the nails that you want to rust. 

Step 4: Let the nail sit in the solution. Any part of the nail that is sitting in the solution will form rust on it. Keep an eye on your nail, and when you are happy with how rusty your nail has become you can carefully take it out of the solution. 

Step 5: Let the nail air-dry. Wear gloves and carefully remove the nail from the solution. If you wipe down the nail you may lose some of the rust finish. Place it gently on a paper towel and let it air dry. In a few hours, your nail should look rusty and you can check it out a little closer.  Be sure to safely drain your solution and dispose of your gloves.

What is the Science? 

So what is rust anyway?

Rust forms on metals in a process called oxidation. Oxidation occurs when certain metals, like iron, are exposed to oxygen. For some metals this happens very quickly, and for others this process is a little slower. Metals that are protected by paint and other coatings will not rust because those coatings are protecting the metal from being exposed to oxygen. If some part of the coating is removed or damaged (like a scratch on a car, or paint on a bicycle wearing off) the metal will then be exposed to oxygen and the process of rusting can begin. 

What is actually happening when rust forms?

In our experiment, mixing hydrogen peroxide (H 2 O 2 ) and distilled vinegar together creates a small amount of something called peracetic acid. Acid is corrosive and can cause things like metal to break down. Hydrogen peroxide is made of hydrogen and oxygen, but it’s the oxygen that’s key to creating rust on metal.  

The molecules of iron on the surface of the nail exchange atoms with the oxygen in the solution and produce a new substance. You guessed it–rust! (or iron oxide as scientists would call it!)

This whole process is helped along by the salt we added to the solution. Its job in this whole process is to act as an electrolyte which lowers the electrical resistance in the solution, helping the oxygen and the nail to trade atoms more easily. 

** Atoms are the pieces that make up a molecule. These are super tiny and impossible to see with your own eyes, so scientists have to use very powerful equipment to see these tiny building blocks**

Why am I noticing so many changes?

Any time you see bubbling, fizzing, or a color change, that is a clue that you’re probably seeing a chemical reaction. This means that our iron is changing. Once the nail undergoes the process of rusting we can remove the rust from the nail, but the iron that turned to rust will never go back to being iron. 

You might also notice the reaction getting warm. This particular chemical reaction is an exothermic reaction, meaning a chemical reaction that produces or gives off heat. This is one of the reasons we want to be sure to use proper tools and safety equipment throughout the entire experiment. If the nail is too warm for you to comfortably touch, use a kitchen utensil like tongs to remove your nail, or pot holders to safely relocate your container.  

Ask Your Young Scientists

As you begin combining ingredients to make your solution, ask:

• They may see and hear some fizzing, some bubbling, the salt disappearing (dissolving) into the mixture, and they may notice that the mixture is clear but gets cloudy as the salt is added 

Once the nail is in the solution, ask your scientists:

• They may see and hear more fizzing or bubbling, the color changing, they may notice that the container feels a little warmer after a few minutes, or even see rust beginning to form on the nail
• Your scientist may wonder why the color of the solution is changing, why it is bubbling, they may wonder why the solution has a different smell. They might wonder what rust actually is.

Once the nail is out and dry, ask your scientist to make a few comparisons between a rusty nail and a non-rusty nail. 

• What things are different? 
• What things stayed the same?

More to Explore

The amount of time you leave the nail sitting in the solution will determine how rusty your nail gets. If you only want a little bit of rust, try taking your nail out after a few minutes. If you want a really rusty nail, try leaving your nail in the solution all day, or maybe longer. You can leave the nail in the solution for as long as you want, but keep in mind that the container may get very warm if the nail rusts for an extended period of time.

Try this same investigation again but with a twist. Either use another nail or wipe off the nail you just used with a paper towel.  Before you put the nail into the solution try covering it in petroleum jelly.  Will it still rust? Let’s find out! 

This content was made possible in part by the Institute of Museum and Library Services.

We want to see what you try at home. share your experiments with us on social media by using the #scienceatplay and tagging @ctsciencecenter..

Nick Villagra is a STEM Educator at the Connecticut Science Center, responsible for developing and delivering science experiences, including classroom lab programs, stage shows, and vacation camps. Nick holds a Bachelor’s of Science in Engineering from Swarthmore College. and has been a speaker at the New England Museum Association conference. Always looking to put a unique stamp on the Science Center’s offerings, Nick enjoys incorporating custom-designed 3D printed materials for students to interact with.

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Rusty nail experiment

Follow FizzicsEd 150 Science Experiments:

You Will Need:

• 6 Test tubes or plastic cups
• 6 Steel nails (avoid galvanised ones)
• Lemon juice
• Cooking oil.
• Optional: Saltwater, detergent.
• Adult supervision

• Instruction

Set up the 6 test tubes or cups as shown in the picture above. This experiment is very much about  variable testing !

Take a photo and write down your observations of each nail at the start of the experiment. This is also a good time to enter this into your own  classroom blog !

Optional: Weigh each nail with an accurate scale at the start and the end of the experiment.

Optional: Try different nails in the same liquid… do they rust differently?

Over the coming days take recordings of each nail’s condition.

– Which nail showed rust first? – If you were able to weigh each nail at the end of the experiment, was there any difference between the nails? Why?

This setup is just one way of running this classic rust experiment. You could also try the following experiment conditions too:

• nail completely submerged in water vs. half submerged.
• nail completely submerged in water with a layer of oil over the top of it.
• nail in salt water vs. nail in pure salt

You could also try normal steel nails vs. steel wool to investigate the effect of surface area on rusting rates as well.

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Why Does This Happen?

Rusting is the oxidation of metal, whereby the oxygen in the environment combines with the metal to form a new compound called a metal oxide. In the case of iron rusting, the new compound is called iron oxide… also known as rust!

This science experiment is all about controlling variables to explore which material will rust an iron nail first.

Variables to test

More on variables here

• Try boiling the water… does this make the nail rust faster, slower or is there no impact on the rusting time?
• What happens when you use different liquids?
• If you scratch the nail first, will it rust faster or slower?
• What if you use iron wool and iron filings instead?
• Try galvanised nails

Further information

Rusting, also known as corrosion, is the reddish-brown layer formed over an iron when exposed to air and water. Rusting occurs mainly because of a chemical reaction between iron with water and oxygen in the air.

Simple formula…     

Water + Oxygen + Iron = Rusting

The chemical reaction usually occurs very slowly and it is an oxidation process. Rusting can also occur on other metals such as copper and they may not always be called ‘rust’.

Rusting can also occur in water. The carbon dioxide gas in the air mixes with water to form a weak acid called carbonic acid. This acidified water can dissolve some of the iron and water begins to break down into oxygen and hydrogen. The free oxygen reacts with the dissolved iron to form iron oxide or rust.

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27 thoughts on “ Rusty nail experiment ”

How many day will nail rust in tap water,vinegar,salt water, sprit and cooking oil

Hi Kolwawole! Thanks for your question. The time to rust for the nail is highly dependent on the liquid the nail is immersed in. In water, you tend to see the beginnings of rust within a couple of days or so whereas other liquids take longer. Try the experiment out and let us know your results!

I bought non galvanised steel nails (they are called bright steel) and I have had them in my liquids (salt water and tap water) for a week now and instead of showing signs of rust they have just gone a grey colour. Do you know why? How can I adjust the experiment to make them actually rust? Thanks

Interesting! It looks like that if your nails were non-galvanised, it would have been to do with dissolved minerals such as carbonates in your water. The more carbonates, the ‘harder the water’. The harder the water the more difficult it is to rust a hot-dip galvanised nail as it affects the pH and the action of sodium and chlorine ions that come from the dissolved salt in the water ( see this link ). The thick layer of Chromium and Zinc on the galvanised steel slows the rusting as it prevents oxygen reaching the metal (at least for a while). You can actually see this affect by scratching off part of the galvanised layer and then letting this area rust as you’ve removed the protection ( read up on crevice corrosion ).

The thing is, your bright steel nails are non-galvanised. This means they should have little to no protection to the salt. If left for longer, the nails should begin to corrode on the outside. The rust formed on the outside is still permeable by the water and salt ions, which means that we would expect this rusting to happen underneath the top layer of rust as well. This should continue until the nail becomes completely iron oxide (rust). Let us know if this happens! For full details on the chemistry of nails rusting, check out csun.edu.

Thanks for your question!

I’m really confused about how can I weigh corrosion in metals. Can you please help.

Hi Rouzana! If you are able to have access to laboratory scales within a high school, you should be able to take a measurement of each nail mass before and after the experiment. The more sensitive the scales, the better!

hi can you please tell me the aim and the hypothesis of this experiment. thanks

Hi! Here’s something that could start you off; – Aim; To determine which liquid produces the most rust on an iron nail. – Null Hypothesis; There will be no change in rust on an iron nail when immersed in ‘ABC liquid’. Have fun!

Hi! Do you know what type of reaction this and also the science behind it? Thank you!

Hi Lara! This is an example of a Redox reaction, wherein this case the iron reacts with water and oxygen to form hydrated iron(III) oxide, which we see as rust. See further details here!

I wanted to do a variation of this experiment for my high school class. Instead of weighing the change in mass to determine the amount of oxidation, I was wondering if there was a chemical that could dissolve only the nail(iron or any other metal) leaving the remaining iron oxide behind.

Sorry Michelle, I’m not sure of a chemical that will do this. If you find out please let us know!

hey can you tell us the chemical formula of the equation iron+water+oxygen= hydrated iron(III) oxide Should we cover the bottle of water to hasten the rusting process ? thank you

Hi Viv! There’s actually a few things going on here over three separate reactions: A great summary of the three reactions can be found here The final balanced equation is below, however this covers both Fe(II) and Fe (III) ions. 4Fe + 3O 2 + 6H 2 O → 4Fe(OH) 3

If I have four solutions (water, salty, bleach and with oil) which will corrode the fastest? the slowest?

Hi!, I placed screws/nails in vinegar and lemon juice and after 9 days they turned black, I was wondering what is the cause of this?

Hi! The acid from both liquids removed the outer coating and exposed the underlying metal to the air which caused oxidation

hi, I have a doubt, I used the ss steel screw ( nail) and I kept them in vinegar, cooking oil & lemon juice. But when I checked it in the next day the screw in the vinegar turned silver to black. The same happened the same but it happened to the lemon juice

Hi! Both the vinegar & lemon juice are acids that removed the coating and allowed the underneath to oxidise.

What is their rate of corrosion (Reaction)? thank you

Hi! This is dependent on the concentration of the acids and the temperature

what are the factors that affect/speeds-up corrosion?

Solution concentration & type as well as temperature. Isolate a variable and see which make the greatest effect!

what liquid makes nails/screws rust the fastest?

Hi Piper! Please try the experiment to find out and let us know!

Do you know what are the independent, dependant and controlled variables in the experiment.

Hi! Please have a read of this article to help you with this answer 🙂 https://www.fizzicseducation.com.au/articles/variables-teaching-the-heart-of-science-experiments/?recaptcha_response=

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Oxidation Experiment: Does It Rust?

This post may contain affiliate links.

We did a rust oxidation experiment this week that was really fun to watch. We wanted to know what things will rust and why. Plus we measured which ones rusted the quickest!

How to Do the Rust Oxidation Experiment:

My kids gathered a bunch of different metal objects from around the house. We got nails, screws, paper clips, staples, bobby pins, brads, etc. We put them all into little paper cups of water. and let them sit for a week.

My kids wanted to try some with salt water, too. So half of ours are in salt water. We did it randomly & not in the most scientific way! 🙂 I think a few extra things were added in during the week, too.

(To make a more scientific experiment, try double of each, one set in in salt water and one set in fresh water and compare the difference.)

Each day we observed the changes to see which ones were rusting. This photo shows the first signs of rust.

What is Rust?

Rust is the reddish brown compound called iron oxide that forms when iron an oxygen react in the presence of water and air, hence the term oxidation.

There are ways to speed up rusting and ways to slow it down. To speed it up metal objects can be immersed in water. Salty water speeds it up even more.

To prevent  rust ,  iron  can be coated to prevent the reaction. You can do it through painting metal or through galvanization.   Galvanization  involves coating an  iron  object with a protective layer of  zinc which helps prevent that reaction, or slow it way down. 

A few of the objects we tested had been galvanized (paper clips, staples, and one of the nails). We also added in a bobby pin with had a paint coating on it. Those things did not rust. The tip of the bobby pin, where there is no paint, did end up rusting, though!

It was a fun experiment to try!  We learned some interesting things.

You may also be interested in another oxidizing experiment that we did with apples browning a while back.

This is part of the A-Z Guide to Understanding STEM hosted by Little Bins for Little Hands.

Former school teacher turned homeschool mom of 4 kids. Loves creating awesome hands-on creative learning ideas to make learning engaging and memorable for all kids!

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Science project, bust that rust.

This project can be done by a variety of different ages.  Younger students can experiment with making steel wool pads rust and trying to find substances that might prevent rusting.  High school students can appreciate the chemistry involved.

Difficulty of Project

$7.00 for poster board and steel wool pads

Approximate time to complete the project

Project goal.

The goal is for all students to learn how rust occurs and how to prevent rusting.

Materials and Equipment

• A box of steel wool pads.  Although the soap-less kind is preferable, the ones with soap will work equally well.
• At least two or three of the following:  clear fingernail polish, spray-on car wax, furniture polish, polyurethane finish, and vegetable oil.
• Four saucers or small bowls

Introduction

Rust is a problem almost everywhere in the country except the southwest.  It’s the cause of bridges collapsing (such as happened in 1967 when the Silver Bridge in West Virginia collapsed, killing 46 drivers), cars prematurely aging, and fire escapes failing.  Even your bicycle is not immune from this problem as fenders often become rusty, especially as water slicks up in this area.

Since rust is such a problem, it’s natural to demand an explanation. Rust occurs as iron oxidizes.  This oxidation happens when iron (and its alloys such as steel) is exposed to water or air with high water vapor content.  Iron rusts faster when exposed to salt water, which is why salting snowy roads is hard on cars.  Likewise, bridges over salt water (such as the Golden Gate Bridge) need more regular maintenance.  This is one of the reasons that acid rain caused by pollution is so harmful.

In these experiments, students use steel wood pads to explore how rust occurs.  They will have the opportunity to develop their own anti-rust measures, using clear nail polish, spray-on car wax, vegetable oil and other coatings. Background information

Oxidation occurs when an element (in this case, iron) loses an electron.  Both water and oxygen are required for oxidation – which is why cars in the dry southwest have so little rust compared to cars in rainy Florida.  We see even more rusted-out cars in New England where icy roads are regularly salted. This is because oxidation occurs faster when water is slightly acid.

Iron can be rust-proofed with a variety of water-repellant coatings.  In these experiments, students can try various water-repellent substances that encourage water to “bead-up” – therefore minimizing contact with the water.

High school and older middle school students may be interested in learning in learning the chemistry of oxidation.

Chemistry of Oxidation

Oxidation occurs when an element loses an electron.  We say that the oxidation state of the element has increased when it loses that electron.  Oxidation is the first step in the rusting process:

Fe ? Fe2+ + 2 e-

Here, the 2 e- represents two electrons that were liberated from the iron, leaving a charged iron radical.  The charged radical reacts with oxygen in the presence of water as follows:

4 Fe2+ + O2 ? 4 Fe3+ + 2 O2-

Note:  in the above reaction, the oxidation state of iron increases from Fe2+ to Fe3+.  Since both Fe2+ and Fe3+ are inherently unstable, they will try to spit out hydrogen ions as follows:

H2O ? Fe(OH)2 + 2 H+Fe3+ + 3 H2O ? Fe(OH)3 + 3 H+

The resulting Fe(OH)2 and Fe(OH)3 will lose as water (this is called a dehydration reaction), thereby creating  iron oxide (Fe2O3) – which we call rust.

Terms, Concepts and Questions to Start Background Research

• Electron transfer

Experimental Procedure

Experiment #1.

• Dampen a steel wool pad with approximately 2/3 cup regular water and put it in a first saucer.  
• Dampen a steel wool pad with approximately 2/3 cup salt water and put it in a second saucer.
• Make a mildly acidic solution by mixing 1/3 cup vinegar with a 1/3 cup water.  Use all of this solution to dampen a steel wool pad and put it in a third saucer.
• Leave an undampened steel wool pad in a fourth saucer.  This is your control.
• Inspect the steel wool pads at 12 hours, 24 hours, 36 hours, 48 hours, 72 hours and 96 hours.   Which pad rusted the fastest?  The second fastest?  The third fastest? Take pictures of the rusted pads and write up your results.

Experiment #2

• “Pre-treat” steel wool pads by coating them in any of the following:  clear nail polish, spray-on car wax, vegetable oil, polyurethane finish, and furniture polish.   You do not have to use all of these substances, but try to select at least two.  Which do you think will prevent rust the best?
• Dampen your pre-treated steel wood pads with water (just as you did in experiment #1) and put them on a saucer.  Come back and observe the steel wool pads at 12 hours, 24 hours, 36 hours, 48 hours, 72 hours, and 96 hours. Which pre-treatment worked the best?  Why?

Bibliography

• Wikipedia " Rust "
• How Stuff Works " How Does Rust Work? "

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Science Project on Nails That Rust

Chalk and Vinegar Science Projects

If you ever wonder why nails rust, it's because rusting happens when a metal is exposed to oxygen. The "rust" is actually iron oxide and forms when the iron in the nail reacts with the oxygen in the air or in liquids. The molecules of iron on the surface of the nail exchange atoms with the oxygen in the air and produce a new substance, the reddish-brown ferrous oxide, a.k.a. rust. A simple science project tests the effects of different liquids on the rusting process, such as oil, water, vinegar and detergent.

TL;DR (Too Long; Didn't Read)

The rusting process of a nail speeds up considerably when it is in certain types of liquids. Water removes electrons from iron, leaving it positively charged. Oxygen then reacts to the positively charged iron and creates ferrous oxide. Salt water is an electrolyte, which contains charged atoms. Charged atoms cause iron to lose electrons more readily and allow oxygen to bind with the iron more freely, which accelerates rusting.

Things You'll Need

Place numbered test tubes or cups in a line to let you compare the effects of different liquids on your nails. Before you begin your experiment, take a photograph of each nail. You may also weigh each nail at this point. Place one nail in each test tube or cup.

Add a different liquid to each test tube or cup. For example, if you have six containers you could add cooking oil, tap water, vinegar, lemon juice, salt water and detergent. Write down what liquid is in each container. Over several days, take regular notes on each nail's condition. Record which nail showed rust first.

Repeat the above steps, but this time try different conditions. For example, you could compare a nail completely submerged in water to a nail only half submerged in water, or observe a nail completely submerged in water with a layer of oil on the top of it. You could compare a nail in salt water and a nail in pure salt.

At the end of your experiment, remove the nails from their containers. Weigh them to determine whether there is any difference between them.

Wear safety goggles and gloves at all times. If you use bleach or stronger acidic substances in your experiment, have adult supervision.

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• California State University: Rusting Rates of Iron Nails
• University of Illinois at Urbana-Champaign: Q & A: Rate of Rust Formation
• UCSB ScienceLine: Does Saltwater Affect the Production of Rust?

About the Author

Claire is a writer and editor with 18 years' experience. She writes about science and health for a range of digital publications, including Reader's Digest, HealthCentral, Vice and Zocdoc.

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Rusting of Metals

Introduction:

These equations indicate that in order for metals to corrode (rust), two reactions occur; an oxidation that converts metal to metal ions and electrons and a second reaction which consumes those electrons by converting oxygen and water to hydroxide ions. In order for these reactions to occur, the electrons must be transported from the place where the metal dissolves to the place where the oxygen is consumed and an ionic current must also flow between the sites to complete the circuit. This ionic current flows more easily through water containing electrolytes (i.e., NaCl). This accounts for the rapid rusting of unprotected steel in a salty environment.

The final product of iron oxidation (rust) is usually a ferric oxide (often hematite Fe 2 O 3 ). The initial corrosion product of the anodic reaction is ferrous (Fe 2+ ) ion. This is subsequently oxidized to Fe 3+ by exposure to oxygen. In this experiment we are looking at the initial product only.

In this experiment we can watch the corrosion reaction by using substances that produce a color change when they react with the products of the iron oxidation or oxygen reduction. Recall that phenolphthalein turns pink in the presence of hydroxide and ferricyanide turns a deep blue in the presence of iron II ++ (rust). (see experiment #6, Metcalfe, H. Clark, Modern Chemistry , Holt, Reinhart and Winston, 1982, pp. 147-50.

The corrosion process may be slowed by coating the metals with other metals or polymers in order to protect the metal from the corrosive environment. Examples of this can be seen in food cans which have a polymer coating and in galvanized steel where iron is coated with zinc.

When we put two metals in direct contact, one can oxidize (rust) while the other reduces oxygen. This reaction sets up a voltage and is the primary reaction in a battery. By measuring this voltage, it is possible to construct a list ranking the metal's oxidation tendencies. If metals which are far apart in oxidation tendencies are placed in contact with each other and with an electrolyte solution, severe corrosion of one metal can occur. We will examine some of these metal combinations in this experiment.

0.1 M K 4 Fe(CN) 6 ; 0.1 M K 3 Fe(CN) 6 : 0.1 M NaCl solution: phenolphthalein; Al, Cu, Pb, Sn, Zn, 1.5 X 6 cm foil strips; Mg ribbon, 6 cm; mild steel bar 2.5 X 6 cm; galvanized steel sheet, 4 X 4 cm; steel can (food) lids, polymer coated; steel can side, tin coated (use Hunt's tomato sauce can); pennies, new and old (pre-1982).

Safety Note:

Rusting of Steel Using the Salt Drop Technique. (First described in 1926 by U. R. Evans. See Scully, J. C., The Fundamentals of Corrosion , 2nd Ed., Pergamon. 1975. p. 57.)

Procedures:

1. Plain Steel

Obtain 100 ml of salt solution and add 10 drops of phenolphthalein. On a section of mild steel, combine 4 drops of this solution and 3 drops of potassium ferricyanide and cover with a watchglass. Observe for at least five minutes. What changes occur?

On the same bar do as above except use ferrocyanide. Observe for at least 5 minutes. What changes occur? Which chemical reagent (ferro or ferri) would you use to check for rust on iron?

In Figure 1, fill in the colors you see at the proper sites.

Ions are spatially separated in this salt drop experiment because the drop is thicker in the middle than at the edges. Electrochemical reduction reactions that produce OH - occur at the edges due to readily available oxygen from the air. Electrochemical oxidation reactions occur at the middle of the drop due to the lack of oxygen. See Figure 2.

2. Polymer Coated Steel

Using the file, place a deep scratch on one area of a polymer coated steel can lid. Place 3 drops of ferricyanide and 4 drops of salt solution on the scratch. On a second area of the polymer coated lid, place the drops as above and cover with a watch glass. Observe both areas of the lid for at least 5 minutes. What changes occur? Record in Figure 3.

3. Tin Coated Steel

Repeat Procedure 2 using a tin plated steel can side, tin side up. Observe for at least 8 minutes. What changes occur? Record in Figure 4.

4. Zinc Plated Steel

Repeat Procedure 2 using a piece of galvanized steel. Observe for 5 minutes. What changes occur? Is iron rusting? Record in Figure 5.

Unscratched__________________ Scratched ___________________

Observe that an intense pink color forms, indicating a reaction is taking place and OH ions are produced. No blue is seen in the drop-indicating that the iron is not rusting. Metals such as zinc are used because these sacrificial anodes are more willing to give up electrons (oxidize) than the iron and thus protect the iron from oxidation. Let us investigate different metal combinations.

3. A Penny For Your Thoughts

Following Procedures 2 in Part I. use the salt drop technique on each of two pennies with a deep scratch on each (one penny pre-1982 and one post-1982). The new pennies are copper plated zinc. What do you think will happen?

Part II - Galvanic Series (batteries)

1. Voltmeter Ranking of Metals

Fill a wide mouth bottle with salt solution. Hang a copper strip over the side of the jar, and stopper the jar. Abrade all metal strips with sandpaper. Clip one lead from a voltmeter to the copper strip and the second lead to a metal strip into the solution through the hole in your stopper and record the voltage on Table 1. Obtain two more sets of readings from other students; average and calculate the standard deviation. Rank your metals in ascending order of voltage.

2. Galvanic Couples of Metals

Place 2 strips of metal from Table 2 on each other and fold one end of the strips over each other several times. Flip one metal out so that both metals are visible (see figure 7). Place several drops of your salt solution on the junction of the 2 metals. Observe and record which metal turns pink on Table 2. In using Mg, if both metals turn pink, ignore the Mg.

metal A —e--—> metal B

The metal acting as a cathode turns pink therefore the other metal must be the anode and is corroding (rusting). How do the results in Table 2 compare with the voltage ranking on Table 1?

• Explain your observations and conclusions from the pennies experiment above.
• Why does grapefruit juice left in an open can taste metallic?
• If nerves respond to electrical currents, why do you think putting aluminum foil on an amalgam (gray) filled tooth hurts? Dental amalgam is a mixture of Ag, Sn, and Hg.
• Why do they put magnesium rods in a steel hot water heater? (Hint: Think about galvanized steel.)
• If pipes feeding a water fountain were made of copper with lead solder at the junctions, which metal dissolves more readily? Explain.
• Tarnished silver can be restored by contact with magnesium in a salt solution. In this reaction, the tarnished silver is reduced. What is oxidized? (Try this!)
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Tag: rust experiment for kids

The chemistry of rust (oxidation).

That reddish-brown crud we call “rust” is all around us, yet we probably rarely think much about it. It turns out what we call rust is a chemical process that combines iron (Fe) and oxygen (O) to form iron oxide. Thus, by studying rust we are studying chemistry!

The chemical formula is:  4Fe + 3O 2 = 2Fe 2 O 3

What is happening? During this reaction the iron atoms are passing electrons to the oxygen atoms, a transfer that is called oxidation. In the process the atoms are bound together.

Rust Experiments

Because it is a slow process, doing experiments with rust takes a few days.

1. What rusts? (Preliminary free exploration)

• paper clips, small bolts, metal washers and any other small metal objects to check for rusting – let the children brainstorm and gather samples as appropriate
• include some items that probably won’t rust such as pennies or brass brads
• container to hold water

Place a sample of all the objects in a container of water and check them every day for a few days. Leave the rest of the objects nearby or in a similar dry container to compare what happens. See which objects start to show signs of rust and which do not. Let the children touch and smell the objects that have rusted. Do they feel different? Do they smell? Do they look different?

2. What environmental conditions are needed for iron to rust?

Can iron rust in dry air or is water needed? Does the presence of acids, such as acid rain, speed up rust? What about salt? Do the salty roads in winter or salt spray from the ocean really make cars rust faster? What happens when the tannins in tea meet iron/rust? Let’s find out.

Gather for each participant:

• fine steel wool (from paint stores or home supply centers- see note below)
• white vinegar
• teaspoon measure
• tea bags, hot water and container for making tea
• tape and marker for labels
• 5 beakers or similar containers
• paper and pen or pencil to record results

Note:  Why fine steel wool? The coarser steel wool you get to clean dishes is stainless steel, which is resistant to rust. For another experiment, get samples of both and try them side by side.

Note 2: The tea isn’t central to the question, but does react quickly which may engage impatient youngsters who might otherwise lose interest. You may definitely omit it.

Prepare the tea by soaking one or two tea bags in hot water in a container such as a tea mug for about three minutes. Stir briskly and discard tea bags.

Make saltwater by adding 2 teaspoons of salt per 8 ounces of water and stirring.

Label the containers:

Pour 4 ounces (1/2 cup) or roughly 120 ml of water into the first container. Add 4 oz or 120 ml of saltwater to the second container. Add 4 ounces white vinegar to the third container and 4 ounces of tea to the fourth. Leave the 5th container dry.

Break off pea to marble-sized balls of steel wool and roll into 5 small balls. Try to use a consistent amount for each container. Drop the steel wool into each container. Some may float, which is okay.

Rust experiment, before set-up.

Check what is happening after 15 minutes.

After 15 minutes the tea probably has started to darken. The steel wool will have turned black. In the photograph above the steel wool that was in the tea is on the left and steel wool that had been in plain water is on the right.

What is happening? The tannins in the tea are reacting with the iron and rust in the steel wool to make iron tannate. Iron tannate is very stable and people are investigating its use to prevent metals from rusting.

Check again after 24 hours.

The tea, on the right, has turned black with a concentration of iron tannates. The water, on the left, and the saltwater (not shown) are turning brown and the steel wool is beginning to rust.

The vinegar (center) is still clear and the steel wool is not showing rust. Why not? One reason might be that the vinegar has been setting on a shelf in a closed jar and might not have much oxygen in it. How would you test this?

The dry steel wool is not rusting either. Even though the chemical equation shows that only iron and oxygen are needed, the chemical process actually needs some water or another catalyst to be present to get the reaction going.

Record your results again after 48 hours. What has changed? Use your results to plan more experiments.

Can you tell me…

why we paint metal objects like the San Francisco bridge?

_______________________________

A word of caution to educators:

During preparation for this post I came across a couple of references to experiments that promised “fast rust.” These experiment required mixing bleach and vinegar. Mixing bleach and vinegar is not a good idea! The acid reacts with the bleach releasing chlorine gas. In small amounts the chlorine gas reacts immediately with the iron to give iron chloride, which looks like rust. If you add an excess amount, however, toxic chlorine gas might possibly be released.

About.com has more information

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Corrosion experiment - Rusting nails

Corrosion of metals is an electrochemical process (Redox reaction) and fundamentally it requires 4 components:

Cathodic reaction (Reduction reaction, positive polarization): A reaction that gains electrons. As a result, the oxidation number decreases. For instance, hydrogen and oxygen reduction reactions are common in acidic and aerated solutions, respectively. The site where the cathodic reaction occurs is called the cathode.

Proton reduction reaction 

$$2{H^ + } + 2{e^ - } \leftrightarrow {H_2}(g) \tag{1} \label{eq:1}$$ 

Oxygen reduction reaction

$$ {O_2}(sol.) + 2{H_2}O + 4{e^ - } \leftrightarrow 4O{H^ - } \tag{4} \label{eq:4}$$

Anodic reaction (Oxidation reaction, negative polarization): A reaction that loses electrons. As a result, the oxidation number increases. Generally, this is the metal dissolution reaction. A metal in metallic form, which has an oxidation number of zero, loses electrons and becomes ions. Metal ions can dissolve away or further react with the surroundings, such as with oxygen to form oxides scales. The site where the anodic reaction occurs is called the anode.

Iron oxidation

$${Fe}\rightarrow{Fe^ {2+} } + 2{e^ - } \tag{5} \label{eq:5}$$ 

Zinc oxidation

$${Zn}\rightarrow{Zn^ {2+} } + 2{e^ - } \tag{6} \label{eq:6}$$ 

Electrolyte : a conductive solution to carry ions. Seawater is an effective electrolyte for corrosion due to high salt concentration. Coastal regions are thus more susceptible to corrosion than areas further in land due to deposition of salt aerosols.

Electrical conductor : an electrically conductive medium to transport electrons. For instance, an electrical wire connecting two metal pieces, direct contact between dissimilar metals, or the metal itself.

Different metals have different tendencies to corrode, thus some would corrosion more readily than others (i.e., we say they would be more anodic). In fact, local anodes and cathodes develop even on the same metal surface as they are heterogeneous. 

The dissimilar metal corrosion and the effect of heterogeneities in metals on corrosion are demonstrated using steel nails in an agar gel with a pH indicator and ferrous ion indicator. In these examples, the steel nail corrosion was accelerated when electrically connected to copper and was mitigated when connected to zinc. The time-lapse videos show colour changes as reactions proceeded.

Nail - Zinc

Nail - Copper

When it is simply just the steel nails in agar, corrosion still occurred. This is because of metal heterogeneities and cold work (bending).

Nail - straight

Nail - Bent

We developed a supplementary note to further explain science behind this experiment, some troubleshooting, and additional resources.

Kod Pojtanabuntoeng

Associate Professor

Keep up to date with all the latest research, subscribe:

Experiment: Investigating the rusting of iron

Experiment: investigating the rusting of iron- updated 2024.

Investigating the rusting of iron

ZIMSEC O Level Combined Science Notes: Experiment: Investigating the rusting of iron

Aim:  Investigating the rusting (oxidation) of iron

Materials:  4 iron nails, 1 steel nail, a piece of copper/brass, 5 test tubes, cotton wool, solid calcium chloride, magnesium ribbon

• Half fill two test tubes with water
• Put an iron nail in one test tube and label it A and a steel nail in another tube label it B
• Put an iron nail in a dry test tube and label it C and plug with a small piece of cotton wool on which a few pieces of calcium chloride are placed.
• Calcium chloride is a drying agent
• Wrap a piece of magnesium ribbon around and an iron nail and put it into the fourth test tube and label it D fill it with water
• Half fill the remaining test tube with boiled water. Put an iron nail with a layer of oil to exclude air and label the tube E
• Leave the test tubes for a few days and observe the results

Results and Observations

• The iron nail in test tube A will be covered with a layer of rust after a few days
• There is very little if any rust on the steel nail in test tube B
• There is no rust observed on the iron nail in test tube C
• There is no rust/little rust on the iron nail in test tube D
• There is no rusting on the iron nail in test tube E
• Iron is susceptible to rusting
• Rusting can only occur in the presence of moisture (water) and air
• Controlling humidity ( test tube C) prevents rusting
• Galvanising using a more reactive metal such as zinc prevents the rusting of iron
• Oiling reduces/prevents rusting

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Lesson Explainer: Rusting Chemistry • Third Year of Secondary School

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In this explainer, we will learn how to explain the conditions necessary for rusting and learn how to write balanced equations for the key reactions involved.

Rust is a reddish-brown substance often found on the surface of old or abandoned metal, such as an old car, can, or nail.

Rust is a form of corrosion that builds up over time on iron or iron alloys when they are exposed to oxygen and water. Before learning about the chemical formation of rust, let’s take a look at its physical properties.

The formation of rust can reduce the strength and stability of an iron object because of the difference in physical properties between iron and rust. An engineer that uses an iron beam in a structure will want it to remain a strong, durable, and dense beam instead of one that will expand, crack, and chip away.

In order to prevent rust, engineers can use coatings, such as oil, paint, or other metals, to prevent the surface of the metal from making contact with water and oxygen in the surroundings. They can also select rust-proof alloys such as stainless steel.

Example 1: Identifying Methods That Prevent Rusting

Which of the following suggestions is not a viable method of slowing or preventing rusting?

• Plating with tin
• Soaking in salt water
• Covering with plastic
• Coating with grease

Most of these answer options slow or prevent rust from forming. The question is asking us to find the one option that does not slow or prevent rusting.

Rust forms when iron is exposed to oxygen and water. In order to prevent rusting, we need to prevent the exposure of iron to oxygen and water.

Knowing this, one option leaps out as different: soaking in salt water certainly does not limit the exposure to water. Also, since there is oxygen dissolved in water, it does not limit the exposure to oxygen either.

The other four options—painting, plating, covering, and coating—all involve protective layers that prevent iron from contacting water and oxygen.

The correct answer is option C, soaking in salt water.

Definition: Rust

Rust is a flaky, reddish-brown hydrated iron(III) oxide formed through the oxidation of iron in the presence of oxygen and water. It has the chemical formula F e O H O 2 3 2 ⋅ 𝑛 .

Definition: Corrosion

Corrosion is the gradual destruction or damage caused by a slow, irreversible, and spontaneous redox reaction between the surface of a substance and the environment.

Note that all rust is corrosion, but not all corrosion is rust. Other metals can oxidize or otherwise corrode to form various compounds, but only iron will form the compound we call “rust.”

Chemically, rust is hydrated iron(III) oxide, with the chemical formula F e O H O 2 3 2 ⋅ 𝑛 . The “ 𝑛 ” signifies that the number of water molecules in the compound can vary.

The simplified reaction for the formation of rust is: 4 F e + 3 O + 2 H O 2 F e O 2 H O 2 2 2 3 2 𝑛 ⋅ 𝑛

This overall reaction shows that iron combines with oxygen and water to form a hydrated oxide. However, to understand the chemical process in more detail, let’s look at the intermediate reactions.

The first step is the oxidation of iron to iron(II) ions, as shown by the following half reaction. Oxidation is the loss of electrons, and this formation of ions happens as the solid iron becomes a solution: F e ( ) F e ( ) + 2 e s a q 2 + –

In the corresponding half reaction, oxygen is reduced, accepting electrons from the reaction above in the presence of hydrogen ions to form water: 4 e + 4 H ( ) + O ( ) 2 H O ( ) – + 2 2 a q g l

As well as reacting to form water, the hydrogen ions and the dissolved oxygen in the water further oxidize iron(II) ions into iron(III) ions: 4 F e ( ) + 4 H ( ) + O ( ) 4 F e ( ) + 2 H O ( ) 2 + + 2 3 + 2 a q a q a q a q l

The iron(III) ions combine with water to form iron(III) hydroxide: F e ( ) + 3 H O ( ) F e ( O H ) ( ) + 3 H ( ) 3 + 2 3 + a q l s a q

Finally, the iron(III) hydroxide dehydrates to form hydrated iron(III) oxide with chemical formula F e O H O 2 3 2 ⋅ 𝑛 .

In summary, iron dissolves in water to form iron(II) ions that are then oxidized into iron(III) ions. Hydrogen ions are absorbed, and water is produced along the way. The iron(III) ions then combine with water to make iron(III) hydroxide, which then forms hydrated iron(III) oxide.

With this process in mind, we can take a look at some of the factors that might increase the rate of rusting of a piece of iron. The simplest way to affect the rate of reaction is to change the exposure to the two main reactants, water and oxygen. For example, if we coat the iron in grease so water and oxygen cannot reach it, no rust will develop. Conversely, if we leave an iron object outside in the rain for many days, it will rust more quickly than if it is kept dry.

The iron in objects near the sea, such as boats and chains, also tends to rust quite quickly, as can be seen in the photo below. Interestingly, exposure to salt water increases the rate of rusting compared to fresh water. The oxidation–reduction reaction at the beginning of the rusting process requires the movement of electrons. The ions present in salt water make it a more effective electrolyte than fresh water, allowing electrons to be transferred more easily and rust to form more quickly.

It is worth noting that even underwater iron can rust as there is oxygen dissolved in the water. The rust can clearly be seen in the following photograph of a propeller from a Japanese ship that was sunk during the second world war.

However, if we took water and boiled it to remove the dissolved oxygen, that water would not cause a piece of iron to rust.

Other reactants in this process are hydrogen ions. Hydrogen ions are absorbed during both the reduction of oxygen and the formation of iron(III) ions, so an increase in the concentration of hydrogen ions will speed up these processes. In addition, the hydrogen ions increase the electrical conductivity of the solution, so the electron transfer in the redox reaction happens more quickly.

Acid rain can also erode protective coatings, allowing the process of rusting to begin on the iron underneath. For these reasons, an acidic environment with a low pH will cause iron to rust more quickly.

Example 2: Describing the Effect of Salt on Rusting Processes

Rusting of iron is an example of a redox reaction. The rate of rusting of iron in water varies with increasing salt concentration.

• Oxygen atoms
• Hydrogen atoms
• The rate increases because dissolved ions aid the decay of metal nuclei.
• The rate increases because dissolved ions aid the movement of electrons.
• The rate decreases because dissolved ions aid the ionization of water.
• The rate decreases because dissolved ions react with dissolved oxygen.
• The rate increases because dissolved ions react with the metal atoms.
• Oxidizing agent
• Reducing agent
• Electrolyte

This question is asking about the process of oxidation. Oxidation–reduction reactions involve the transfer of electrons from one compound or element to another. Oxidation involves a loss of electrons, while reduction involves a gain of electrons. During oxidation, iron gives up electrons to form iron 2+ ions. So, the correct answer to this part of the question is “electrons.”

This question is asking how and why salt changes the rate of reaction of rusting. To answer this question, we need to determine whether it increases or decreases the rate of reaction and the mechanism behind that change.

Part of the correct answer is that increasing salt concentration increases the rate of rusting. Iron that is either near salt water, or areas where roads are salted, rusts relatively quickly compared to metals in other environments. We can eliminate options C and D from consideration.

Next, why does salt increase the rate of reaction for rusting? As we mentioned in the first part of this question, the oxidation–reduction reaction that occurs at the beginning of rusting involves the transfer of electrons. The faster those electrons can move, the quicker the reaction will occur. In a salt solution, the electrons can move faster. Looking at the answer options, this fits with option B, the rate increases because dissolved ions aid the movement of electrons.

Option A describes the decay of metal nuclei, but radioactive decay is not involved in the rusting process. Option E suggests that the rate increases because of a reaction between the metal atoms and salt ions, but during rusting, the metal atoms react with the water and the oxygen in the solution, not the salt ions.

So, the correct answer is option B, the rate increases because dissolved ions aid the movement of electrons.

This question is asking us to define the role of salt in the rusting process.

Salt cannot be the oxidizing or reducing agent, as it does not accept or donate electrons in the oxidation–reduction reaction.

While some salt solutions can be acidic or basic, the function of the salt in this case is not as an acid or a base. Any salts will increase the rate, not just those that dissolve into hydrogen ions or hydroxide ions.

In the previous part of this question, we determined that the purpose of the salt is to aid the movement of charged particles through the solution. A substance that allows the movement of charged particles is called an electrolyte. Option E, electrolyte, is the correct answer.

The industry and manufacturers are very concerned about the risk of rusting. This concern is due to the widespread use of steel and the detrimental effects that rust has on the properties of iron. These negative effects impact the properties of the metal much more significantly than corrosion in many other metals.

Rust is the specific name for hydrated iron(III) oxide formed during the corrosion of iron, but there are other metals that corrode to form oxides as well. For example, aluminum corrodes in the presence of oxygen in the following reaction: 4 A l ( ) + 3 O ( ) 2 A l O ( ) s g s 2 2 3

Aluminum can corrode in other ways, such as in the presence of a chloride, but this way is the most common. We can compare and contrast rust with aluminum oxide to better understand the negative effects of rusting.

Patches of rust can easily chip away after they have formed, exposing more iron to be rusted; however, aluminum oxide does not chip away easily. The oxide coating on aluminum forms very quickly, resealing the aluminum if the surface is scratched or chipped.

Another negative effect of rusting is the fact that iron expands when it corrodes into rust, while aluminum contracts when forming aluminum oxide. These two physical characteristics make rust a much more disruptive oxide for machines and structures. Aluminum oxide will form a thin, dense layer on the outside of the metal that will not noticeably affect its volume. However, rust expands as freshly exposed metal deeper in the metal begins to rust.

Rust has a much more significant effect on the properties of iron than corrosion in other metals. The fact that rust can chip, cause the object to expand, and penetrate deep into the piece of metal shows the significant negative effects that need to be mitigated. Depending on the use of the piece of iron and the time and severity of the rust, the strength of the piece of iron can be compromised, making it unfit for purpose.

Example 3: Identifying Differences Between the Oxidation of Iron and Aluminum

Why does rusting affect iron more than aluminum?

• Aluminum oxides are less soluble than iron oxides.
• Aluminum is less reactive than iron.
• Aluminum oxides are less stable than iron oxides.
• Aluminum is protected by a surface oxide layer.
• Aluminum binds to water less strongly.

This question is asking us to identify a key difference between the oxidation of iron and aluminum. This oxidation process can happen when the metal is exposed to water and air. One reason why the oxidation of iron causes significant changes is that the rust can chip away. When it chips, more iron is exposed that can then rust as well.

The reason aluminum is not as affected by oxidation is that aluminum oxide does not chip. Instead, it forms a thin coating on the outside of the metal. Aluminum is more able to hold its shape and strength when it oxidizes. The correct answer is option D, aluminum is protected by a surface oxide layer.

To be thorough, we can take a look at the other options as well. Aluminum oxide and rust are equally insoluble, so option A is incorrect. Aluminum is more reactive than iron and its compounds are more stable as a result, so options B and C are incorrect as well. Option E is insignificant, as water molecules do not readily bind with aluminum molecules due to the strong oxide coating.

Different sets of conditions cause rust to form at different speeds. We can use a simple experiment to demonstrate which combinations of conditions cause rusting to happen most quickly.

Demonstration: The Effect Different Conditions Have on the Formation of Rust and the Rate of Rusting

• Place an iron nail into five separate test tubes.
• Set up different conditions for each test tube as shown in the image below.

Observation

The iron nail in test tube E will begin to rust first, followed by the iron nails in test tubes C, B, and A. The iron nail in test tube D should be the last to start rusting.

Explanation

Rust occurs when iron is exposed to both water and oxygen. In test tube D, the iron nail is placed into dry air where no oxygen is present. The anhydrous calcium chloride removes any remaining water that might be present. The iron nails placed into test tubes A and B contain either water or oxygen, but not both. So, here, rusting will be slow to occur. The iron nail in test tubes C and E are exposed to both oxygen and water. However, test tube E contains salt water, and since the presence of ions increases the rate of rusting, then the iron nail in C will rust more slowly than the iron nail in E.

• Rusting occurs quickest when iron is exposed to salt water and oxygen.
• Rusting occurs slowest when iron is protected from water and oxygen.

Example 4: Identifying the Necessary Conditions for the Rusting of Iron

Iron nails are placed into three sealed bottles containing different materials, as shown.

• 1, 2, and 3

Rusting occurs when iron is exposed to both water and oxygen. In order to answer this question, we must identify the different conditions in each of the bottles. All three bottles are sealed; however, there is still air, which contains oxygen, present inside.

In bottle 1, the iron nail is placed into boiled water with air being present. The importance of using boiled water is that boiling will reduce the amount of oxygen gas present in the water. However, oxygen from the air will dissolve into the water, and so the iron nail will likely be exposed to oxygen and water. So, rusting is likely to occur.

In bottle 2, the iron nail is again placed into boiled water. However, the water is covered with a layer of oil that will prevent oxygen from the air from dissolving in the water. Even though the iron nail is in the water, the lack of oxygen present means that rusting is unlikely to occur.

In bottle 3, there is no water present, only air and some calcium chloride. The air might contain both oxygen and water vapor; however, the calcium chloride will remove moisture from the air. As a result, the iron nail in bottle 3 is exposed to oxygen from the air, but not to water. Therefore, rusting is unlikely to occur.

Since rusting is likely to only occur in bottle 1, the correct answer is option A.

The calcium chloride in bottle 3 will remove any moisture that is present in the air. During this process, the anhydrous calcium chloride will form a hydrated salt according to the following equation: C a C l ( ) + H O ( ) C a C l H O ( ) 2 2 2 2 s l s 𝑛 ⋅ 𝑛

This reaction is not oxidation or reduction, so we can exclude options A and B. The calcium chloride is not dissolving in a solvent and therefore is not acting as an electrolyte, so we can conclude that option E is not correct.

Calcium chloride is not involved in the process of rusting and, as there is no other chemical reaction occurring, it is not acting as a catalyst.

This means that calcium chloride is acting as a desiccant. A desiccant is a substance that can induce a state of dryness, often by absorbing water. The correct answer is option C, desiccant.

• Rust is a reddish-brown substance that forms when iron is exposed to water and oxygen.
• Rust is weaker, more brittle, and less dense than iron, so the formation of rust can negatively impact iron objects and structures.
• The chemical formula for rust is F e O H O 2 3 2 ⋅ 𝑛 .
• The formation of rust is a multi-step process wherein dissolved iron ions combine with water to make iron(III) hydroxide, which then dehydrates into rust.
• Rusting occurs more quickly when there is increased exposure to oxygen or water. It also occurs more quickly when the iron is exposed to salt water or an acidic solution.
• Rust is particularly harmful when compared to other oxides, such as aluminum oxide, as it will expand and crack more as well as chip away to corrode further.

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Chemistry for the gifted and talented: rusting

By Tim Jolliff and Kirsty Patterson

• No comments

Dive to greater depths in your understanding of the factors that affect the rate of rusting with this lateral thinking problem

This resource accompanies the article  Raising expectations . The activity originally appeared in the book  Chemistry for the gifted and talented .

Learning objectives

• Develop higher order thinking skills including lateral thinking and creative thinking.
• Design a valid investigation which models one of the factors that might affect the rate of rusting at different depths below sea level.

Introduction

This activity looks at rusting in the context of shipwrecks. It aims to develop higher order thinking skills including some lateral thinking and creative thinking. It has different demands to the traditional experiment to show the factors needed for rusting to occur .

Download this

A lateral thinking problem exploring the factors that affect the rate of rusting in the context of shipwrecks. Learners produce a concept cartoon and plan an experiment.

Resources in this package include a student worksheet as MS Word and PDF , a student support sheet as MS Word and PDF , teacher guidance notes (including a discussion of the answers) as MS Word and PDF , a technician sheet as MS Word and PDF and a presentation as MS Powerpoint and PDF .

Prior knowledge

Learners will need to be familiar with the topic of rusting in order to be able to ask probing questions and design an appropriate experiment. Learners will need to be confident with the following scientific ideas:

• Rusting of iron requires oxygen and water.
• Salt speeds up rusting.
• The sacrificial protection of iron by more reactive metals, such as zinc or magnesium.

The questions on slide 8 help to assess and activate this prior knowledge and free up working memory so that learners can use the higher order thinking skills.

Teacher notes

This resource is best used as a teacher-led class discussion using the accompanying Powerpoint presentation. The discussion will lead on to group and practical work. The lateral thinking section could be used as a lesson to follow on from an introduction to rusting of iron. The experiment design section is optional and the activity can be used without it.

Part 1: Lateral thinking exercise

The learners may not have met these before and you might want to go through an example with them – ‘Anthony and Cleopatra lie dead on the floor (in a pool of water)’. The learners ask questions which require a yes or no answer. Answer the questions to help your learners discover that Anthony and Cleopatra are goldfish whose bowl has fallen on the floor when the shelf, on which it was sitting, broke.

In the lateral thinking exercise in this activity the shipwreck in deeper water was carrying a cargo of zinc and magnesium. Learners in need of more challenge could devise their own lateral thinking problems, perhaps for homework.

Ask your learners to design a concept cartoon on the predictions about the shipwrecks. They can do this all together or in groups. The cartoon should have a drawing in the middle showing the shipwrecks at different depths and four speech bubbles around it expressing opinions about why one will be rustier than another. The support sheet contains templates for learners who do not want to draw the central image. The best cartoons will be those with the greatest number of plausible explanations. An example of a good concept cartoon is given on slide 11. It might be a good idea to do a group effort on a different topic on the board before the students produce their own. One example could be four opinions on: whether mayonnaise is a liquid or a solid; whether magnesium would dissolve in acid on a space station; what climate change will mean for the UK; who is doing the greater good for humanity, the doctor or the research scientist working on a cure for cancer.

Part 2: Planning an investigation

Learners will plan an investigation to investigate one of the factors that affect the rate of rusting. The planning itself is the aim of the exercise, but if you also want your learners to carry out their planned investigations it will need some advance preparation. A suggested list of some apparatus required is included for technicians.

Learners may find it difficult to get reliable results and should be encouraged to run their experiment more than once so that they get an idea of the reliability. A couple of methods they could try for measuring the amount of rusting are: weighing the dried rust after filtering or weighing the nails and recording the mass lost as rust.

Practical notes

The actual requirements will depend on the plans written by the learners.

If the class are going to carry out their plans it is a good idea to ask your science technician, if you have one, which pieces of glassware they are happy to leave nails in to rust. There is advice about rust stain removal in CLEAPPS Bulletins 103 and 108 .

The practical may need to be left for some time (a week or more) so you will need to check with the technician or other teachers in your department which equipment will need to be returned if it needs to be used again during that time. Agree a suitable place where the experiment can be stored between lessons to prevent it being cleared away prematurely or tampered with in a way that might affect the results.

• Thermometers
• An electronic balance
• Water pumps
• Apparatus to draw air through the mixture in a boiling tube
• Distilled water
• Cooking oil
• Emery paper
• Filter paper

More resources

• Challenge pupils to balance sinking against floating , with a toy submarine concept from  In search of solutions .
• Use this concept cartoon to stimulate class discussion about the factors that affect rusting  and find more concept cartoons in our collection.
• Try this practical to test the corrosion of metals in dry air, moist air and air polluted by acidic sulfur dioxide from the Nuffield practical collection .
• Check out job profiles for an Environmental chemist  and a Professor of environmental chemistry on the Future in chemistry website .

Shipwrecks presentation

Shipwrecks student sheet, shipwrecks student support sheet, shipwrecks teacher notes, shipwrecks technician notes, shipwrecks powerpoint, additional information.

This resource originally appeared in the book  Chemistry for the gifted and talented  by Tim Jolliff. The resource was reviewed and additional content added in July 2022 by Holly Walsh and Kirsty Patterson.

• 11-14 years
• Presentation
• Applying scientific method
• Problem solving

Specification

• use scientific theories and explanations to develop hypotheses
• 2.2.3 investigate experimentally rusting as a reaction of iron with water and air producing hydrated iron(III) oxide (other practical activity); and
• 2.2.4 demonstrate knowledge and understanding of the methods used to prevent iron from rusting, including barrier methods such as painting, oiling, plastic coating and suitable metal coating or plating (galvanising), and explain sacrificial protection…
• 2. Develop and use models to describe the nature of matter; demonstrate how they provide a simple way to to account for the conservation of mass, changes of state, physical change, chemical change, mixtures, and their separation.
• 4. Classify substances as elements, compounds, mixtures, metals, non-metals, solids, liquids, gases and solutions.

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• Physical and Chemical Changes
• Rusting Iron Prevention

Rusting of Iron

Table of Contents

What is the Chemistry Behind the Rusting of Iron? Why is Rusting an Undesirable Phenomenon? Factors that Affect the Rusting of Iron How can Rusting be Prevented?

Rusting of iron refers to the formation of rust , a mixture of iron oxides, on the surface of iron objects or structures. This rust is formed from a redox reaction between oxygen and iron in an environment containing water (such as air containing high levels of moisture). The rusting of iron is characterized by the formation of a layer of a red, flaky substance that easily crumbles into a powder.

This phenomenon is a great example of the corrosion of metals, where the surfaces of metals are degraded into more chemically stable oxides. However, the term ‘rusting’ is generally used to refer to the corrosion of objects made of iron or iron-alloys.

What is the Chemistry Behind the Rusting of Iron?

The exposure of iron (or an alloy of iron) to oxygen in the presence of moisture leads to the formation of rust. This reaction is not instantaneous, it generally proceeds over a considerably large time frame. The oxygen atoms bond with iron atoms, resulting in the formation of iron oxides. This weakens the bonds between the iron atoms in the object/structure.

The reaction of the rusting of iron involves an increase in the oxidation state of iron, accompanied by a loss of electrons. Rust is mostly made up of two different oxides of iron that vary in the oxidation state of the iron atom. These oxides are:

• Iron(II) oxide or ferrous oxide. The oxidation state of iron in this compound is +2 and its chemical formula is FeO.
• Iron(III) oxide or ferric oxide, where the iron atom exhibits an oxidation state of +3. The chemical formula of this compound is Fe 2 O 3 .

Oxygen is a very good oxidizing agent whereas iron is a reducing agent. Therefore, the iron atom readily gives up electrons when exposed to oxygen. The chemical reaction is given by:

Fe → Fe 2+ + 2e –

The oxidation state of iron is further increased by the oxygen atom when water is present.

4Fe 2+ + O 2 → 4Fe 3+ + 2O 2-

Now, the following acid-base reactions occur between the iron cations and the water molecules.

Fe 2+ + 2H 2 O ⇌ Fe(OH) 2 + 2H +

Fe 3+ + 3H 2 O ⇌ Fe(OH) 3 + 3H +

The hydroxides of iron are also formed from the direct reaction between the iron cations and hydroxide ions.

O 2 + H 2 O + 4e – → 4OH –

Fe 2+ + 2OH – → Fe(OH) 2

Fe 3+ + 3OH – → Fe(OH) 3

The resulting hydroxides of iron now undergo dehydration to yield the iron oxides that constitute rust. This process involves many chemical reactions, some of which are listed below.

• Fe(OH) 2 ⇌ FeO + H 2 O
• 4Fe(OH) 2 + O 2 + xH 2 O → 2Fe 2 O 3 .(x+4)H 2 O
• Fe(OH) 3 ⇌ FeO(OH) + H 2 O
• 2FeO(OH) ⇌ Fe 2 O 3 + H 2 O

One similarity between all the chemical reactions listed above is that all of them are dependent on the presence of water and oxygen. Therefore, the rusting of iron can be controlled by limiting the amount of oxygen and water surrounding the metal.

Why is Rusting an Undesirable Phenomenon?

Rusting causes iron to become flaky and weak, degrading its strength, appearance and permeability. Rusted iron does not hold the desirable properties of iron. The rusting of iron can lead to damage to automobiles, railings, grills, and many other iron structures.

The collapse of the Silver Bridge in 1967 and the Mianus River bridge in 1983 is attributed to the corrosion of the steel/iron components of the bridge. Many buildings made up of reinforced concrete also undergo structural failures over long periods of time due to rusting.

Rusted iron can be a breeding ground for bacteria that cause tetanus. Cuts from these objects that pierce the skin can be dangerous.

Since rusting occurs at an accelerated rate in humid conditions, the insides of water pipes and tanks are susceptible to it. This causes the pipes to carry brown or black water containing an unsafe amount of iron oxides.

Factors that Affect the Rusting of Iron

Many factors speed up the rusting of iron, such as the moisture content in the environment and the pH of the surrounding area. Some of these factors are listed below.

• Moisture: The corrosion of iron is limited to the availability of water in the environment. Exposure to rains is the most common reason for rusting.
• Acid: if the pH of the environment surrounding the metal is low, the rusting process is quickened. The rusting of iron speeds up when it is exposed to acid rains . Higher pH inhibits the corrosion of iron.
• Salt: Iron tends to rust faster in the sea, due to the presence of various salts. Saltwater contains many ions that speed up the rusting process via electrochemical reactions.
• Impurity: Pure iron tends to rust more slowly when compared to iron containing a mixture of metals.

The size of the iron object can also affect the speed of the rusting process. For example, a large iron object is likely to have small deficiencies as a result of the smelting process. These deficiencies are a platform for attacks on the metal from the environment.

How can Rusting be Prevented?

Iron and its alloys are widely used in the construction of many structures and in many machines and objects. Therefore, the prevention of the corrosion of iron is very important. Some preventive methods are listed below.

Alloys that are Resistant to Rusting

Some alloys of iron are rust-resistant. Examples include stainless steel (which features a layer of chromium(III) oxide) and weathering steel.

COR-TEN steel rusts at a relatively slower rate when compared to normal steel. In this alloy, the rust forms a protective layer on the surface of the alloy, preventing further corrosion.

Galvanization

• Galvanization is the process of applying a protective layer of zinc on a metal. It is a very common method of preventing the rusting of iron.
• This can be done by dipping the metal to be protected in hot, molten zinc or by the process of electroplating .
• Zinc is a relatively cheap metal that sticks to steel easily. It also offers cathodic protection to the iron surface by acting as an anode. The zinc layer is corroded instead of the iron due to this.
• The disadvantages of galvanization are that it only provides protection from corrosion for a limited amount of time since the zinc layer is eaten up in the process. It is not very effective in highly corrosive areas (where cadmium coating can be used instead).

Cathodic Protection

• Providing the metals with an electric charge can help inhibit the electrochemical reactions that lead to rusting.
• This can be done by making the iron/steel a cathode by attaching a sacrificial anode to it.
• This sacrificial anode must have an electrode potential that is more negative than that of iron.
• Metals that are commonly used as sacrificial anodes are magnesium, zinc, and aluminium. Once they are corroded away, they must be replaced in order to protect the iron/steel.

Many types of coatings can be applied to the surface of the exposed metal in order to prevent corrosion. Common examples of coatings that prevent corrosion include paints, wax tapes, and varnish.

Smaller objects are coated with water-displacing oils that prevent the rusting of the object. Many industrial machines and tools made of iron are coated with a layer of grease, which lubricates the metal to reduce friction and prevents rusting at the same time.

To learn more about the rusting of iron and other related concepts, such as the corrosion of metals , register with BYJU’S and download the mobile application on your smartphone.

Frequently Asked Questions – FAQs

What are physical and chemical changes.

A chemical transition is the result of a chemical reaction, and a physical change occurs where the structure of matter changes but not the chemical identity. Examples of chemical transformations include fire, frying, rusting, and rotting. Examples of physical changes are to simmer and freeze.

What defines a chemical change?

Chemical reactions requiring the rearrangement of atoms of one or more compounds and the modification of their chemical properties or structure resulting in the creation of at least one new substance: iron rust is a chemical alteration.

Is Melting zinc a chemical change?

A chemical reaction is a mechanism that happens by converting one or more compounds into one or more other compounds. No chemical reaction is registered. However, if the mixture absorbs energy in the form of heat, the zinc may react chemically with the sulphur to form the compound zinc sulphide (ZnS).

Which process is a chemical change?

Material modifications arise as a substance becomes a new material, called chemical synthesis or, similarly, chemical decomposition into two or three distinct compounds, combined with another. These mechanisms are called chemical reactions, and they are usually not reversible or by additional chemical reactions.

What is the importance of chemical change?

Chemical processes allow one to understand matter’s properties. We can learn its chemical properties by observing the way a sample interacts with another matter. These properties may be used to classify an unknown specimen or to predict how different kinds of matter may react with each other.

Put your understanding of this concept to test by answering a few MCQs. Click ‘Start Quiz’ to begin!

Select the correct answer and click on the “Finish” button Check your score and answers at the end of the quiz

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Wow wonderful

very helpful

what is iron

Iron is a mineral, and its main purpose is to carry oxygen in the hemoglobin of red blood cells throughout the body so cells can produce energy.

What is the definition of Corrosion ?

Corrosion is when a refined metal is naturally converted to a more stable form such as its oxide, hydroxide or sulphide state this leads to deterioration of the material.

What is meant by unbalanced chemical equation ?

An unbalanced chemical equation lists the reactants and products in a chemical reaction but doesn’t state the amounts required to satisfy the conservation of mass.

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