silver nitrate copper wire experiment

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Displacement reaction of silver nitrate and copper metal

By Adrian Guy 2008-09-01T00:00:00+01:00

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Watch silver crystals grow in this captivating experiment

For me, this is one of the most beautiful demonstrations. Watching fractal-like silver crystals grow is captivating, whatever your age.

Forming silver crystals

This demonstration can be used as a simple introduction to reactivity or to provide an in-depth discussion of electrochemistry.  

Source: Adrian Guy

• 0.1 mol dm -3  silver nitrate solution (irritant: skin and eyes); 
• Pipette dropper; 
• Petri dish; 
• Microscope with 40× zoom; 
• Copper foil (0.3 mm thickness); 
• Scissors; 
• tweezers; 
• View camera attached to microscope; 
• or microscope with integrated digital camera; 
• Laptop computer and a projector (all optional). 

Silver nitrate solution is an irritant, wear eye protection and avoid skin contact.

Procedure 

Using scissors, cut a very thin slice from the copper sheet. From this slice, cut off the smallest speck that you can see and handle, thus ensuring you have freshly cut edges which are not corroded. Using tweezers, put the speck on a petri dish and place the dish under a microscope. (Note: for smaller microscopes a glass slide can be used instead of a petri dish.)  

Focus the microscope on the copper using  ca  40× magnification (I use a 10× eye piece and 4× object lens). Carefully add one drop of silver nitrate solution to the copper and refocus the microscope. Crystals of silver will start to grow from the edges of the copper. Enough silver is produced at this magnification to fill the view within minutes. 

To show the demonstration to a class of students link a microscope to a view camera, or as I do, use a microscope with an integrated digital camera set at 40× magnification, linked to a laptop computer which is linked to a projector. By using a microscope with an integrated digital camera still images can be recorded, printed and included in the students' notes.  

An alternative way to demonstrate this displacement reaction is to drop a 5 cm piece of 0.5 mm copper wire into a 8 cm depth of silver nitrate solution in a boiling tube. The displacement reaction can be seen with the naked eye, but the crystalline structure of the silver is hard to make out.  

Special tips 

Most microscopes have the light source positioned below the sample platform, which produces a dark outline of the crystals formed. I switch off the light source and, on dark days, shine an LED, clamped in position using a retort stand and clamp, onto the sample from above to see the silver crystals in their true glory. If it is a sunny day, natural light can be used by positioning the microscope near a window.  

Take care not to reflect direct sunlight. If this is focused by a lens it can cause blindness.

When you add the silver nitrate to the copper, the speck of copper can become suspended on the surface tension of the drop. You will need to sink the copper before the reaction will work effectively. The three dimensional crystal structures will not stay in focus because their thickness varies and so constant focal adjustments are required. 

Teaching goals

By investigating a series of displacement reactions leaners aged 11–14 can learn about the reactivity series of metals. Set up a series of test-tube reactions to investigate the displacement reactions between metals such as silver, lead, zinc, copper and magnesium and the salts ( eg  sulfate, nitrate, chloride) of each of the other metals. (Note: 0.1 M lead nitrate is toxic.) Alternatively, you can do this in microscale using spotting tiles, which can be laid out in the same format as the table students use to record their results. 

• See How to teach displacement reactions at 11–14  for more ideas and tips.
• Watch our  reactivity series of metals  practical video to see metal displacement reactions set up in microscale (at 10:35) and find additional resources.

When teaching age 14-16 students about metallic bonding in the structure and bonding topic this demonstration can be used to illustrate the crystalline structure of metals.  

Post-16, students 'enjoy' this simple experiment as an introduction to electrochemistry. The experiment is by no means an electrochemical cell under standard conditions employing a salt bridge, 1 mol dm -3  solutions, and using a high resistance voltmeter to reduce current flow, but it is worth showing to post-16 students.  

By seeing the crystals grow, students can imagine the Ag +  ions pulling electrons off the silver crystals, which in turn remove electrons from the lump of copper and produce copper ions, thus setting up a simple electrochemical circuit. For each copper ion that forms in solution, two silver ions will add to the silver crystal structure.  

This is important to demonstrate because students might hold the misconception that the reaction takes place by silver ions colliding with the copper, which is not the case. 

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What Happens When You Put Copper Wire in Silver Nitrate?

• The Chemistry Blog
• Posted on April 4, 2018

Jessica Clifton

One of the most fascinating chemical experiments is the reaction between silver nitrate and copper wire in water. Characterised by fractal-like precipitates, this experiment is a stunning example of a simple redox reaction.

When you place a copper wire into a solution of silver nitrate and water, crystals begin to appear. These grow on the copper and form a crystallised structure. But before we get in to why this happens, we must first take a look at the components involved.

In this post:

What is Silver Nitrate?

Silver nitrate is a caustic chemical compound with the formula AgNO 3 . Interestingly, it was previously known as lunar caustic by ancient alchemists who associated silver with the moon.

Silver nitrate is highly soluble in water and other solvents. It is also less sensitive to light than its silver halide relatives, and is made by dissolving large amounts of silver in nitric acid.

Even though silver nitrate is poisonous if ingested, it has a variety of applications in medicine where it is used for its antiseptic properties. Silver nitrate is also used as the forerunner in most silver compounds, including those used in photography.

What is Copper?

Copper (Cu) is one of the only metals that doesn’t require extraction from an ore. This is because its natural form is directly usable.

Copper has weak metallic bonds, which is why it is one of the more ductile metals. While copper is known for its reddish colour, it is also recognised for its green pigment – think of the Statue of Liberty, for example.

This green layer is actually a protective coating known as patina. It forms when copper has been exposed to air for a long period of time, and provides protection against further corrosion.

The Reaction

When a copper wire is introduced into an aqueous silver nitrate solution, a single replacement reaction occurs. This is when two elements in a reaction swap places, one replacing the other. This is a type of redox reaction. 

At the beginning of the experiment, the pure elemental form of copper (Cu) is oxidised by the silver nitrate solution. This means that it loses electrons and forms copper ions. These ions replace the silver ions that are present in the aqueous silver nitrate solution to form a new compound: copper nitrate.

Meanwhile, the opposite process happens to the silver nitrate. Rather than losing electrons, the silver ions in the nitrate solution gain electrons as they undergo reduction. This changes them into their elemental form (Ag) which replaces the elemental copper. This reaction is also known as a redox reaction, and we can express it in the following way:

Copper Metal (Cu) + Silver Nitrate (AgNO 3 ) = Silver Metal (Ag) + Copper Nitrate (CuNO 3 )

As the silver nitrate is converted into its elemental form, the deposits of silver coat the surface of the copper wire where they continue to accumulate over time. This forms a captivating crystalline structure around the wire.

Sometimes, the crystal-like precipitates are later separated from the copper and used in pieces of fractal artwork.

The solution at the end of the experiment is a characteristic blue colour. This is because of the presence of copper nitrate, which appears blue because of its ability to absorb the white light that passes through a solution. This happens with most transition metals.

Check out the video below which demonstrates how this reaction occurs:

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Replacement Reaction: Silver onto Copper

Metallic copper is placed in a solution of silver nitrate. Silver metal forms at the surface of the copper metal. Copper nitrate is seen turning the solution blue as the reaction progresses.

Silver nitrate stains the skin. It is also an oxidizer.

Chemicals and Solutions

• Copper sheet or wire
• 0.5M or 1.0M silver nitrate

Crystallizing dish or beaker

Form the metal into an easily recognized design (UW is a popular choice). Place the dish with the metal on the overhead. Pour silver nitrate over the metal. The formation of silver metal will blur the image as the reaction progresses.

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Demonstration: Silver Tree And The Reactivity Series

Every element on the periodic table is as unique as the next, differing in color, toxicity, boiling points, magnetic properties, and of course, reactivity. Chemical reactivity is an important predictor of reactions, sometimes shown in a simplified form known as the reactivity series. Learn about it through a step-by-step demonstration of the famous ‘Silver Tree’ experiment that you can try at home!

The silver tree is a result of the different reactivities of metals. When we add copper metal to silver ions, the more reactive copper loses its electrons (is oxidized) to the less reactive silver (is reduced). The oxidized copper moves into the solution, while reduced silver becomes a solid. This silver metal is what causes the ‘tree’ to form.

Before we begin the demonstration, we need to give you a little background on the experiment. As with all well-written lab reports, it’s important to have an introduction that tells us what the reaction is trying to prove. In this case, it’s about how metals have different reactivities.

Metals Have Different Reactivities

The reactivity series.

he most reactive metals include sodium and potassium which can react with cold water, catch fire and explode. Meanwhile extremely unreactive metals on the bottom—like gold and platinum—can even be found naturally in their pure metallic form due to their low reactivity 1 . Metals are nicely placed in order of most to least reactive in a list known as the reactivity serie s, shown below.

Extracting Iron from Ore

In the real world, we can take advantage of the reactivity series to do useful chemistry! An example is to use carbon is used to extract metallic iron from rocks (ore).

The iron ore found in nature is in the form of iron (III) oxide (also known as haematite). When we heat iron ore together with carbon, the more reactive carbon ‘steals’ oxygen atoms from the iron. The less reactive iron is happy to give up its oxygen atoms, forming iron metal and carbon dioxide as waste 2 .

Iron (III) oxide + Carbon → Iron + Carbon dioxide 2Fe 2 O 3 + 3C → 4Fe + 3CO 2

The reactivity series is a basic but useful tool for predicting displacement reactions—seeing if a metal will displace another metal in a compound.

Displacing Silver with Copper

The ‘Silver Tree’ demonstration provides a fantastic visualization of such reactions. From the reactivity series we see that copper is more reactive than silver, so we predict that copper will displace silver in a solution of silver nitrate:

Silver nitrate + Copper → Silver + Copper nitrate 2AgNO 3 + Cu → 2Ag + Cu(NO 3 ) 2

Being extremely easy to set up, copper metal is added to a silver nitrate solution. Silver metal crystals grow out like beautiful fuzzy branches covered in sparkly leaves from the surface of the copper, giving the reaction the famous ‘Silver Tree’ moniker. As an extra, the solution takes on a blue hue as copper nitrate is formed; perhaps comparable to the bleak blue sky on a winter’s day. Lovely. Definitely a festive experiment ready to celebrate the winter season with a sparkly snowflake -coated chemis -tree!

Now, lets hop into the demonstration to see how we can do this at home! As always, safety first. The team recommends reading the risk assessment below if you plan on repeating the demonstration yourself.

The Silver Tree Reaction: A Demonstration

Risk assessment.

Author’s Personal Safety Notes:

• Gloves and goggles should always be worn when handling chemicals to protect your sensitive eyes and skin.
• Silver nitrate is extremely sensitive to light, causing decomposition. It can be very reactive so is best stored and handled away from bright light and other chemicals. Stains skin and clothes brown, protective gear such as a lab coat should be worn to limit skin exposure.
• Copper (II) nitrate is produced in the reaction which is harmful to ingest and irritating to the eyes. If in contact with eyes, immediately wash for at least 10 minutes. Prolonged contact is certainly not good, but from experience though if you get this on your skin it is hardly dangerous if washed off immediately. It clings to protein though, so contact with your hair or nails can stain them blue, with the stain only removed by cutting the dyed body part off!

Preparing The Silver Tree

Preparing the Silver Tree demonstration is simple. The reactants are only: – 0.1M Silver nitrate solution 4 – Thick copper wire The concentration of the silver nitrate solution is not hugely important, but we recommend 0.1M. To prepare this, we weighed 1.36g of silver nitrate into a 100ml glass beaker.

Next, we added 80ml of distilled water to the beaker. The silver nitrate crystals were dissolved by giving them a good stir.

Wallah! 0.1M silver nitrate solution. Next up, the copper wire can be bent into shape and we’re ready to proceed.

Growth of the Tree, In Pictures

Once ready to begin, the copper wire can be lowered into the solution. We held it in place with a clamp – this way the copper doesn’t touch the bottom nor move around.

Now sit back, relax, and enjoy watching these sparkly crystals appear before your very eyes! The demonstration should last for 30 minutes to an hour, depending on the concentration of your silver nitrate solution 5 . The following pictures of our experiment were taken over the course of just over an hour:

It is a beautiful little experiment, although I will admit a little ugly near the end yet still extraordinary! The silver crystals grow as silver nitrate molecules and copper atoms collide, up until the surface of the copper wire is covered in silver crystals. At this point, the silver acts as a barrier to protect the copper inside from further reaction. Instead, silver ions (Ag + ) now pull electrons off the silver crystals themselves, which in turn removes electrons from the copper wire to produce copper ions (Cu + ), thus setting up a simple electrochemical circuit 6 !

Explaining The Silver Tree Reaction

Redox (reduction and oxidation).

The Reactivity Series is great for predicting reactions such as the beautiful Silver Tree we just witnessed, but we can even go one step further. Here is the Silver Tree reaction equation again:

We can simplify the overall equation by removing ions that don’t lose or gain any electrons – spectator ions – which are not actually chemically involved in the reaction. In this case, the nitrate ion (NO 3 –  ) is the spectator ion, let’s go ahead and remove it:

Silver ion + Copper → Silver + Copper ion 2Ag + + Cu → 2Ag + Cu 2+

By presenting the ‘bare bones’ of a chemical reaction, we can better see the movement of the electrons. Notice the silver ions with a positive charge became two silver atoms (without a charge). This suggests that each silver ion gains a single electron each to be converted from Ag + to Ag; therefore two electrons were gained in total. Because the silver ions gained electrons, we say the silver was reduced. Where do these two electrons come from? We see that the copper atom was converted from Cu to Cu 2+ ; therefore two electrons were lost in total. Because the copper atom lost electrons, we say the copper was oxidised 7 . Due to both reduction and oxidation occurring in this reaction, the Silver Tree is an example of a redox reaction, ‘ redox ‘ being short for ‘ red uction and ox idation’. To help remember the difference between reduction and oxidation, there is a popular acronym:

OIL RIG O xidation I s L oss, R eduction I s G ain

Standard Electrode Potentials

Using our chemical detective skills, we deduced that copper lost two electrons to silver in the Silver Tree reaction. We can work out the fate of both the copper and silver ions in ionic half-equations:

Copper → Copper ion + Electrons Cu → Cu 2+  + 2e –

Silver ion + Electron → Silver 2Ag + + 2e – → 2Ag

Not only do half-equations help put oxidation and reduction into perspective, but they also have predictive power like the reactivity series. Each reaction can be assigned a standard electrode potential or the ‘electrochemical energy’ of a reaction. It may seem a little complicated, but here are the standard electrode potentials for the copper and silver half-equations we just looked at:

Cu 2+ + 2e – → Cu ;  E = +0.34V Ag + + e –  → Ag ;  E = +0.80V 8

Copper has a lower standard electrode potential than silver at 0.34V, which indicates a more reactive metal. Think of it as the metal with a more negative standard electrode potential will be more willing to lose its negative electron(s).

The Electrochemical Series

By listing all half-equations in order of smallest (most reactive) to largest (least reactive) standard electrode potentials , metals can be compared just like the reactivity series and is likewise called the electrochemical series.

In the Silver Tree, the difference in potentials can be calculated between silver and copper. 0.80 – 0.34 = 0.46 V, which means the reaction is predicted to proceed. As a general rule, metals involved in a reaction with less than a 0.4 V difference in their standard electrode potentials are unlikely to react or do so extremely slowly. Although it may seem to be a simple little experiment, the Silver Tree demonstration involves redox chemistry and does so with such beauty. With such an easy preparation to grow pure crystals of sparkly silver metal, this has to be a festive treat for all budding chemists!

This article was written by Samuel Hutchins-Daff . Author’s Note: I hope you learned something interesting today and gained a little appreciation for this tried and tested chemistry demonstration—it would make my day if you did! If you have any further questions don’t hesitate to drop us an email here !

• Oxford English Dictionary, https://en.oxforddictionaries.com/definition/native_metal, (Accessed December 2018)
• BBC Bitesize, https://www.bbc.com/bitesize/guides/zpcdsg8/revision/4, (Accessed December 2018)
• CLEAPSS Student Safety Sheets, http://science.cleapss.org.uk/resource/student-safety-sheets-all.pdf, (Accessed December 2018)
• The Home Scientist, http://thehomescientist.blogspot.com/2010/04/experimehnt-silver-tree.html#, (Accessed December 2018)
• Walter R. Carmody, Jack Wiersma, J. Chem. Educ. , 1967, 44 (7), p 417
• Royal Society of Chemistry, https://eic.rsc.org/exhibition-chemistry/displacement-reaction-of-silver-nitrate-and-copper-metal/2020046.article, (Accessed December 2018)
• Sam Holyman, David Scott, Victoria Stutt, OCR A Level Chemistry A Student Book 2 , Pearson Education Limited, London, 2015
• HyperPhysics, http://hyperphysics.phy-astr.gsu.edu/hbase/Tables/electpot.html, (Accessed December 2018)

About the Author

This article was written by a contributor. For a full list of guest writers, click here .

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lab s-3 copper in silver nitrate

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Lauren's Chemistry Blog

Silver/ copper replacement lab.

Copper wire reacts with aqueous silver nitrate. The relative amounts (moles) of reactant and product are determined from the mass loss of copper wire, the starting mass of sliver nitrate, and the mass of sliver metal obtained. Copper will be changed from its elemental form, Cu, to its blue aqueous ion form, Cu2+(aq). At the same time, sliver ions (Ag+(aq)) will be removed from solution and deposited on the wire in the elemental Ag metallic form.

Like every lab there is always hazards so be careful the hazards in this lab was handling silver nitrate solutions will lead to black stains where it is spilled. It is also poisonous. Be especially careful to avoid getting it in the eyes.

There where three days to this lab each day a different thing was to be done,

Day 1. obtain a 30 cm length of bare copper wire, and then clean it and coil it to fit from the top of the beaker to the bottom. weigh the coil as accurately as possible with the balance. weigh the weighing dish of sliver nitrate and record its number. transfer the contents of silver nitrate to your test tube. pour distilled water into your test tube until the water is about 2 cm front he top. cover the top of the test tube with parafilm. place your thumb on top of the test tube and invert it until all the sliver nitrate has dissolved. add the copper to the test tube and observe the reaction. set the test tube aside.

Day 2. weigh a piece of filter paper for use in separating the silver. shake the test tube and copper wire to dislodge the sliver. set up the funnel with your filter paper in it. lay the copper wire on a labeled piece of paper to allow it to dry. allow the contents to drain over night.

Day 3. weigh the copper coil and record its mass. weigh the sliver and filter paper record the mass.

After all three days you have come to the end of the experiment and you of course have to record your data and answer some questions

Mass of sliver nitrate= 1.04g

Mass of copper coil before reaction= 3.48g

Mass of copper coil after reaction= 3.27g

Mass of copper reacted= .21g

Mass of filter paper and sliver= 2.24g

Mass of filter paper= 1.537

Mass of silver produced in reaction= 0.703

8. Using your starting amount of sliver nitrate, how much Ag should be formed in grams

We estimated about 0.6604/SggAg would be formed and after the lab was over and we collected our information we collected  0.7 grams Ag which is relatively close to what we guessed we would get.

9. using your starting amount of sliver nitrate, how much Cu became Cu(NO3)2 in the reaction we estimated 0.19455064g Cu and the amount we lost when the lab was over was 0.2 grams lost and that is also close to the amount we estimated.

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Silver Crystal Tree Chemistry Demonstration

In this simple chemistry demonstration or crystal project you’ll grow a silver crystal tree. This is a variation of the classic method of growing silver crystals on a copper wire.

Silver Crystal Tree Materials

You only need two materials for this project:

• Copper tree – Sheet of copper that has been cut into a tree shape or a tree made from copper wire
• 0.1 M Silver nitrate solution

There are a few different ways to make the tree shape. One of the easiest is spiraling copper wire over a paper or cardboard cone to make a simple tree form.  Another method is wrapping thin copper wires around a thicker wire, leaving the ends of the thin wires out as branches. Another method uses tin snips to cut a tree shape out of a thin copper sheet.

Be careful to use uncoated copper. Because copper oxidizes in air, it is often treated or coated. If your copper has a coating, it’s not the end of the world. Dipping it into dilute hydrochloric acid (muriatic acid) and rinsing it in water removes most coatings and exposes the copper metal.

Grow a Silver Crystal Tree

All you is place the copper tree into the silver nitrate solution. Silver is reduced on the copper, forming silver crystals. Crystals begin forming immediately and should be visible within an hour. Meanwhile, the solution increases in concentration of copper(II) ions and develops a blue-green color.

You can allow the silver crystal tree to sit in an undisturbed location for a day or two for peak crystal growth. When you are finished growing the silver crystals, carefully remove the tree from the solution and use it as a decoration. Silver is a noble metal , so it resists tarnish.

How It Works

A single displacement reaction is responsible for crystal formation:

2 AgNO 3  + Cu → Cu(NO 3 ) 2  + 2 Ag

2 Ag + + Cu → Cu 2+ + 2 Ag

The silver nitrate in water dissociates into silver and nitrate ions. The silver and copper “trade places” so that silver metal takes the place of some copper, while some copper goes into solution. The copper ions change the color of the liquid, making it blue. This is also an example of a redox reaction written as its net ionic equation .

Silver is very far down the metal reactivity series . What this means is copper isn’t the only metal that works for this project. For example, silver also replaces mercury. If you happen to have mercury sitting around, you can place a bead into a container of silver nitrate and see the same effect.

Dendritic Silver Crystals

Silver crystals form dendrites, which look like ferns, branches, or trees (depending who you ask). Another simple project is to place a copper wire in silver nitrate solution and view crystal growth using a magnifying glass or microscope. The intricate structure of the metal crystals develops as you watch!

Here’s an example of the reaction on a piece of copper:

Is silver nitrate too expensive? Another redox reaction coats copper onto zinc and makes copper holiday ornaments . There are other metal crystals you can grow, too.

• Lide, David R., ed. (2009). CRC Handbook of Chemistry and Physics (90th ed.). Boca Raton, Florida: CRC Press. ISBN 978-1-4200-9084-0.
• Todd, Robert H.; Allen, Dell K.; Alting, Leo (1994). “Surface Coating”.  Manufacturing Processes Reference Guide . Industrial Press. ISBN 0-8311-3049-0.

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Mole Ratios: Copper and Silver Nitrate—ChemTopic™ Lab Activity

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The reaction of copper wire with silver nitrate in aqueous solution produces delicate silver crystal growth on the wire surface and the color of copper(II) ions in solution. With the Mole Ratios: Copper and Silver Nitrate—ChemTopic™ Lab Activity, determine the number of moles of reactants and products in the reaction of copper and silver nitrate and calculate their mole ratio, then write the balanced chemical equation for the reaction.

• Stoichiometry
• Balanced Chemical Equation
• Single Replacement Reaction

FREE K-12 standards-aligned STEM

curriculum for educators everywhere!

Find more at TeachEngineering.org .

• TeachEngineering
• Creating Silver Nanoparticles

Hands-on Activity Creating Silver Nanoparticles

Grade Level: 10 (9-11)

(five 55-minute class periods)

Expendable Cost/Group: US $5.00

Group Size: 3

Activity Dependency: None

Subject Areas: Chemistry, Problem Solving

NGSS Performance Expectations:

TE Newsletter

Engineering connection, learning objectives, materials list, worksheets and attachments, more curriculum like this, pre-req knowledge, introduction/motivation, vocabulary/definitions, troubleshooting tips, activity extensions, activity scaling, user comments & tips.

Chemical engineers develop processes to manufacture valuable chemicals through the application of chemistry, math, and engineering principles. Through these processes, they may improve upon existing processes or even create new, more efficient ones. In this activity, students take on the role of chemical engineers by building a valuable compound: silver nanoparticles. These nanoparticles have unique properties that are used in variety of modern applications such as in water treatment, medicine, and electronics. Students also apply the principles of chemistry and engineering to improve the existing manufacturing process.

After this activity, students should be able to:

• Describe the visible signs of a chemical reaction.
• Explain the principle of limiting reactants in chemical reactions.
• Explain why light scattering by nanoparticles produces unexpected colors.
• Refine a chemical process through experimentation.

Educational Standards Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards. All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN) , a project of D2L (www.achievementstandards.org). In the ASN, standards are hierarchically structured: first by source; e.g. , by state; within source by type; e.g. , science or mathematics; within type by subtype, then by grade, etc .

Ngss: next generation science standards - science.

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Do you agree with this alignment? Thanks for your feedback!

International Technology and Engineering Educators Association - Technology

State standards, arizona - science, texas - science.

Each group needs:

• stereo microscope; if this isn’t available in a chemistry lab, check in with your biology department
• 3 disposable polystyrene petri dishes with lids, 100 mm x 15mm
• a piece of copper wire with no insulation, 4 cm (1.5 in) 16-24 gauge in width
• test tube rack
• pipette droppers
• 4 test tubes, 10 mm x 75 mm
• copy of Student Workbook , one per student
• permanent black marker
• deionized (DI) water, at least 1 L per group
• test tube brush
• 6 pieces of Glad Press’n Seal® Wrap, 2.5 cm 2   (~1 in. 2 )
• safety goggles, one set per student

To share with the entire class:

• refrigerator (for storing the tanning solution)
• silver nitrate, 60 ml of 0.2 M solution
• Pu’erh tea to make 250 ml of tannin solution, 40% concentration tea, available in stores or on Amazon
• filter paper circles with a medium flow rate, available on Amazon
• sodium hydroxide, 50 ml of 0.1 M
• distilled vinegar, 50 ml
• A familiarity with basic chemistry lab procedures and awareness of lab safety rules.
• A familiarity using and cleaning lab glassware such as test tubes.
• A basic understanding of the types of chemical reactions and signs of chemical reactions.

Note: this activity could also be used as an introduction to these topics.

Is it possible to turn base metals like copper or mercury into more valuable metals like silver or even gold? An ancient tradition called alchemy that was practiced extensively throughout the middle ages attempted to do just that. The aim of alchemy was to perfect certain objects by, for example, turning them into gold, or to create new substances that would help cure disease or even lead to immortality. While the practice of alchemy ended centuries ago, alchemists helped develop some of the laboratory techniques, theories, and methods that are used in basic scientific exploration, particularly in chemistry and medicine. While we cannot create gold out of thin air through chemistry, we are going to examine some fascinating processes that will allow us to create a type of silver that is used in a variety of modern applications.

(Follow along in the Student Workbook , 1.0 Lab: Introduction )

An atom of silver found in silver metal has an equal number of protons and electrons. Silver metal is metallic, shiny, and makes great jewelry. Silver ions, however, are missing one electron. Silver ions make up a different substance: silver nitrate. Unlike the related metal, silver nitrate is clear, brittle, and dissolves in water, which is why you never see silver nitrate jewelry.

Today we are going to give an electron to the silver ion in silver nitrate, and see if we can make silver metal again.  When an ion gains an electron it is said to be reduced . When a substance loses an electron it is said to be oxidized . Chemistry research suggests that the element copper and tannin—an organic substance found in tea—may reduce silver nitrate by losing one of their electrons. 

When substances are reduced and oxidized it is called a chemical reaction . Some signs of a chemical reaction include: unexpected temperature change, unexpected color change, formation of gas bubbles, or the formation of a new solid substance, also known as a precipitant . We will be looking for signs of a chemical reaction as evidence that we are making silver.

Note to teacher: The introduction is purposefully vague to allow students to discover that they are creating nanoparticles of silver.  The goal is that students will discover empirical evidence before the explanation.

Silver nitrate (AgNO 3 ) reacts with copper (Cu) to form copper(II) nitrate (Cu(NO 3 ) 2 ) and silver (Ag). This can be called a redox reaction because silver nitrate is reduced and copper is oxidized .  This can also be called a single replacement reaction because copper replaces silver in the substance silver nitrate.

Silver nitrate and copper are the reactants and copper(II) nitrate and silver are the products . Silver is a precipitant because it is a new solid substance formed by a chemical reaction between soluble silver nitrate and copper. The balanced chemical reaction looks like:

2AgNO 3   +  Cu  -->  Cu(NO 3 ) 2   +  2Ag

Image 2 shows a magnification of the product of the chemical reaction between silver nitrate and copper. Silver is visible as precipitant dendrites on the copper wire. Copper(II) nitrate is visible as a green powder. Unreacted copper is also visible because it was not the limiting reactant.

The other reaction in the activity is between silver nitrate and tannins. Tannins are a class of many different large chemicals composed of carbon, hydrogen, and oxygen. One tannin is tannic acid, which has the formula C 76 H 52 O 46 . Tannins have many parts called phenols. Phenols can be oxidized and in return reduce silver nitrate. When tannins reduce silver nitrate they also produce nitric acid (HNO 3 ). The balanced redox reaction looks like:

C 76 H 52 O 46    +   AgNO 3    -->  Ag  +  C 76 H 51 O 46   +  HNO 3

Because tannins are large they block silver from growing like the dendrites on the copper wire. The particles of silver metal are so tiny, about 100 atoms, that you cannot see them. They are only a few nanometers across (a millionth of a millimeter) so we call them nanoparticles . The physical appearance of the solution of suspended silver nanoparticles appears brown.

Silver nanoparticles look brown because tiny particles scatter light.  When light scatters, we see colors.  Take cloud formations as an example. Water is not white, but we see white because the droplets of water scatter sunlight. We can also consider eye color. Blue eyes and green eyes do not have blue or green particles in them, but instead they have tiny particles of brown melanin. Melanin scatters light reflected in eyes. If there is some melanin in an eye, you see blue. If there is more melanin, you see green. When nanoparticles of silver scatter light, you see shades of yellow, amber, and brown. 

Before the Activity

• Gather the materials for each group
• The plastic dishes can be the petri dish or its lid – both work in this activity.
• The actual length of the copper wire is unimportant, but should be at least 2.5 cm. (1 in.)
• Each student will need a copy of the Student Workbook .
• Set aside an area in the classroom where students can access and leave their plastic dishes for the duration of this five day activity.
• Create the tannin solution, silver nitrate solution, sodium hydroxide solution, and acetic acid solution before the activity. The tannin and silver nitrate solutions will be used on Day 1 and 4. The sodium hydroxide and acetic acid solutions will be used on Day 4.
• Directions for making the solutions:
• Tannin solution (brew tea)
• Rinse a 250 ml piece of glassware with deionized (DI) water
• Add 10 g of Pu’erh tea
• Fill the glassware with 150 ml of DI water
• Heat to a boil and then boil for 15 minutes (see Image 3)
• Filter about 100 ml of tea using a medium speed filter in a funnel into a clean 500 ml piece of glassware (see Image 4)
• Add 150 ml DI water to make a 40% concentration tea
• Label “tannin,” cover, and add dropper
• Keep refrigerated when not in use; tea will spoil if left out at room temperature

• Silver nitrate solution
• The molar mass of silver nitrate is 170 g/mol
• Rinse a 100 ml piece of glassware with DI water
• Add 2 g of silver nitrate to 60 ml of DI water
• Label 0.2 M silver nitrate, cover, and add dropper
• Sodium hydroxide solution
• The molar mass of sodium hydroxide is 44 g/mol
• Add 0.22 g sodium hydroxide and 50 ml of DI water
• Label 0.1 M sodium hydroxide, cover, and add dropper
• Acetic acid solution
• Rinse 100 ml piece of glassware with DI water
• Fill to 50 ml with distilled vinegar (not diluted)
• Label 0.8 M acetic acid, cover, and add dropper

With the Students

Day 1 (Student Workbook Sections 1.0 to 2.1)

• Start by organizing the students into groups and handing out a copy of the Student Workbook to each student.
• Present the Introduction/Motivation
• Introduce them to the Student Workbook by having them read 1.0 Lab: Introduction and fill in the missing definition blanks.
• Briefly cover Student Workbook , 1.1, 1.2, 1.3, and 1.4 with the students.
• Include extra lab safety practices related to your specific classroom situation.
• Note the location of all of the materials, and demonstrate how to label the test tubes and plastic dishes with a permanent marker.
• Note the location where you expect students to leave their plastic dishes overnight.  Tell the students that moving the plastic dishes after the solutions are poured into them might mix and contaminate adjacent solutions.
• Describe how you want the test tubes cleaned and returned at the end of the lab.
• Tell the students to record their observations in the Student Workbook , 2.0 Worksheet: Observations and to answer the questions in the  Student Workbook , 2.1 Worksheet: Questions . Students will work on the observations and questions together, with each individual recording their answers in their workbook. Students may complete unfinished questions as homework before the next class.
• Have students put on their goggles and follow the setup and procedure in the Student Workbook , 1.1, 1.2 , and 1.3 .
• A few minutes before the end of class, remind students it is time to finish the lab, and refer to Student Workbook , 1.4 .  Remind them to rinse their hands with tap water before they leave the classroom, and remind students that they need to complete Student Workbook , 2.1 Worksheet: Questions for homework.

Day 1 Tips For teachers

Initially the silver precipitant appears like a black coating on the copper wire. Once the dendrites grow longer, the coating takes on a fuzzy silver-gray appearance. The silver color is more obvious in brighter light.

Students may not notice that the solution in test tube A is turning green. It is subtle at low concentrations.  Students might notice it if they compare it to the clear solution in test tube B.

If students do not notice the change in color in test tube D, have them compare it to test tube C. They started as the same color and noticing the color difference is evidence of a chemical reaction.

There is also a visual test for the presence of nanoparticles in solution. Using a laser pointer (if you have one on hand,) shine it through the side of one of the test tubes. Shining the laser through test tubes A, B, or C means you will not see the laser beam inside the solution. If it is test tube D, the presence of nanoparticles scatters the laser light, and you can see the laser beam inside the solution. This technique is similar to using chalk dust to see a laser beam in a classroom.

If students do not finish 25 minutes of observations, just make sure they notice a color change in test tube D and the precipitant in test tube A. The chemical reactions will continue to completion in the plastic dishes after they leave.

It not a problem if solutions touch and mix a little in the plastic dishes. Students will have lots of uncontaminated areas to examine on Day 2.

Remember, at the end of the day store the tannin solution in a refrigerator as they are prone to spoiling.

Silver nitrate solutions react in light to turn a surface black. Clean up spills with water and paper towels and avoid contact with skin. Students rinse their hands with tap water just in case their skin contacted silver nitrate.

It is important for the students to clean the test tubes. Cleaner glassware gives more accurate results.

Day 2 (Student Workbook Sections 3.0 to 5.4)

• Have students turn to  Student Workbook 2.1 Worksheet: Questions and check for completion.
• Start the class by asking students which test tubes had chemical reactions and which ones did not.  Ask them how they know there was or was not a chemical reaction.  Ask them what they think was produced.
• Regardless of the answers, explain that today you will be examining the samples from test tubes A, B, C, and D that dried overnight for more evidence of what was produced.
• If this is the first time students are using stereo microscopes, demonstrate all of the following: how to adjust the magnification; how to adjust the eyepiece; how to use coarse and fine focus, how to place the sample to see different parts; how to turn on lamps above and below the sample.
• Have students collect their plastic dishes from Day 1.
• Have students follow the directions in  Student Workbook 3.0 Lab: Stereo microscope .  This section describes what each substance looks like through a stereo microscope, along with tips and photos.
• Have students complete Student Workbook , 4.0 Worksheet: Observations 2 , describing what substances they see.  There are also questions where students use their own words to describe what each substance looks like.
• Have students return their plastic dish samples and clean their work area.
• Assign students to read Student Workbook , 5.0, 5.1, 5.2, 5.3 , and 5.4 .  

Day 2 Tips for Teachers

Student Workbook 4.0 is the end of the discovery part of the activity. At this point students have many pieces of empirical evidence that they produced silver nanoparticles in test tube D. The readings and particle diagrams in student workbook sections 5.0 to 5.4 explicitly describe what happened in each test tube and connects the students’ empirical observations to the chemical reactions.

The photos in Images 2, 5, and 6 are from actual student samples. The photos were taken with a cell phone camera through a focused stereo microscope eyepiece.  You or your students could take similar photos to share or display.

Student workbook section 5.4 has a particle diagram that describes three reasons for a color change. This sets up the part of the lab where students will use differences in color as empirical evidence.

Save the dried plastic dish samples in case students want to compare what they produce on Day 4 to previous results.

The silver in D will be in a small sheet near the edge where the silver nanoparticles accumulate as the water evaporates. There will also be dendrites of pure silver throughout the dried sample. Each millimeter of a dendrite is 1 million silver nanoparticles in a line. There will be brown staining from the tannins and probably some unreacted silver nitrate crystals in the corners by the petri dish walls.

In test tube B, students get to see what unreacted silver nitrate crystals look like. This will help them when they see the same in other dried samples.

In test tube C, students get to see what unreacted tannin looks like.  This will help them when tannin when they see the same in other dried samples.

Day 3 (Student Workbook Sections 6.0 to 8.0)

• Organize students into their groups and have them complete Student Workbook , 6.0 Worksheet: Questions 2 .  These reflective questions combine their empirical evidence with the informative readings.
• Check each group for understanding.  Have students defend their answers by citing evidence. Ask questions like:
• How do you know that there was no reaction?
• What was your answer to question 9 on Day 1? Why did your answer change?
• What evidence is there that you produced silver?
• Why did it look brown?
• What would happen if I added more silver nitrate to …….?  Why?
• After each group has defended at least one answer, transition to a whole-class discussion.
• Announce to the students that you are now finally convinced that they made silver nanoparticles in test tube D.
• Say to the students: “A chemical engineer would look at the manufacturing process you used to make silver nanoparticles and think of ways to make it better.  If your job was to make silver nanoparticles, how would you want to make the manufacturing process better?”
• Listen to student answers. Afterwards, direct them to read Student Workbook , 7.0 Reading: Silver Nanoparticles 1 , which describes some of the ways a chemical engineer might try to make the manufacturing process better. Direct them to read Student Workbook , 7.1 Reading: Silver Nanoparticles 2 , which covers some of the chemistry principles a chemical engineer might use to change the manufacturing process.
• Inform the students that there will be a lab on Day 3. It will be just like Day 1 except they will use only two test tubes. The first will be a repeat of test tube D, the standard manufacturing process. The second will be unique to each group, a modified process with the goal of improving the manufacturing process in some way.
• Each student group needs to reach a consensus of how they want to change the manufacturing process.  They also need to state how they believe the change will affect the amount, production speed, and size of the silver nanoparticles.  Students also need to state if the change would affect the amount of silver nitrate lost in the production process.
• Each student needs to record their group consensus in Student Workbook , 10.0 Worksheet: Observations 3 , as the answers to questions 23 and 24.
• Assign Student Workbook section 8.0 Worksheet: Complete Particle Diagrams for homework.

Day 3 Tips for Teachers

If students are unsure what change they should make, Student Workbook 7.1 lists a few options to choose.

Section 7.1 mentions a very simplified version of Le Chatelier’s principle.  With nanoparticles the question of reversibility is complicated and a function of particle size and not just product concentration.  In other words, the silver nanoparticle reaction is modeled as non-reversible and Le Chatelier’s principle is modeled as simply adjusting the forward reaction rate rather than the equilibrium point.

Generally, the slower the reaction rate, the smaller the silver nanoparticles. Extending the exposure time to hot or cold temperatures may change the silver nanoparticle size, with the added effect of the samples  not having enough time to evaporate overnight.

Student Workbook 8.0 for homework allows students to use particle diagrams to guide them in their predictions of how changes in the manufacturing process will change the important factors.  Every scenario is an exact copy of the particle diagram for test tube D in student workbook section 5.2 with one change applied.

Day 4 (Student Workbook Sections 9.0 to 10.0)

• Organize students into groups.
• Ask if any group wants to change their improved manufacturing process choice.
• Verify that the students completed Student Workbook 8.0 .
• Have students follow the directions in Student Workbook , 9.0, 9.1, 9.2, 9.3, and 9.4 . Tell them that it is similar to the lab on Day 1.
• Have students record their observations in Student Workbook , table 4, 10.0 Worksheet: Observations 3 .
• A few minutes before the end of class, remind students where they need to leave their plastic dish, with samples D and E, overnight to dry.

Day 4 Tips for teachers

You can use the laser pointer from day 1 to prove students produced silver nanoparticles in both test tube D and E.

When students work on the Student Workbook , 8.0 particle diagrams they may realize that they want to change the manufacturing process in a different way to produce a better or different outcome.

Students are looking for differences between the original manufacturing process, test tube D, and the improved manufacturing process, test tube E. Students are mostly doing the same lab as day 1. They are looking for evidence that E is different from D. Today they will have color change and rate of color change. Tomorrow they will have evidence from the stereo microscope.

Day 5 (Workbook Section 10.1)

• Have students examine their dried samples with stereo microscopes.
• Direct students to complete Student Workbook , 10.1 Worksheet: Questions 3 .
• Have students present their recommendation to the whole class, emphasizing improvements and tradeoffs.
• When they present, ask each group follow-up questions like:
• Why would producing more silver be beneficial?
• What evidence did you have that…?
• You saw ball like shapes in your sample.  What could they be?
• You created smaller silver nanoparticles but you wasted a lot of tannin.  Was it worth it?
• This other group suggested that it would be better to …. Do you agree?
• Collect the completed student workbooks.

Day 5 Tips for the Teacher

The stereo microscope tips listed in 3.0 are still valid.

There can be a lot of empirical evidence generated by comparing sample D and E. 

When comparing the two samples, both might contain a dark silver edge (as in Image 6), a lighter silver band near the edge, and silver dendrites elsewhere. However, one might have wider and denser silver features. Students may interpret that as a process producing more silver nanoparticles.

Students should combine the information from their observations of the chemical reaction in test tubes D and E, their analysis of the D and E dried samples, their previous experience analyzing samples, the information in the readings, and the information in the particle diagrams. Students have many sources to interpret change in silver nanoparticle production.

Without advanced equipment, analysis is very squishy and qualitative, but there are some general patterns.  Slower reactions produce smaller silver nanoparticles (the best change). Lower temperatures, excess silver nitrate, and adding acid all slow down the reaction.  Faster reactions produce larger silver nanoparticles. Higher temperatures, excess tannins, and adding sodium hydroxide increased the reaction rate.

Some of the evidence students may describe when answering the questions in Student Workbook , 10.1 :

• Evidence of producing more silver metal:
• From the reading and prior knowledge: We added more silver nitrate and tannins so we created more silver .
• Test tube: The color is darker than expected.
• Dried sample: We see less silver nitrate in the corner - it all reacted so we produced more silver metal. We see a larger sheet of silver near the edges, so there were more nanoparticles. We see tighter packed and thicker dendrites .
• Evidence of producing less silver metal:
• From the reading and prior knowledge: We used less of one or both of the reactants.
• Test tube: The color is lighter than expected.
• Dried sample: There is more silver nitrate, so less reacted. The size of the silver sheet is smaller. Dendrites are thin and sparse.
• Evidence of producing silver metal faster:
• From the reading and prior knowledge: Hotter temperatures produce a faster reaction. Adding sodium hydroxide speeds up the reaction (Le Chatelier’s principle).
• Test tube: The color changed faster.
• Dried sample: A faster reaction produces larger nanoparticles. The sheet of silver is less smooth, grainier. There are fewer dendrites and more thick clumps of silver.
• Evidence of producing silver metal slower:
• From the reading and prior knowledge: Colder temperatures produce a slower reaction. Adding acetic acid slows down the reaction. Changing the reactant concentrations may change the reaction rate.
• Test tube: The color changed slower.
• Dried sample: A slower reaction produces smaller nanoparticles. The silver dendrites are finer.
• Evidence of wasting more silver nitrate:
• From the reading and prior knowledge: We added more silver nitrate and there already was excess silver nitrate.  We added less tannin, so there would be excess silver nitrate.
• Test tube: Excess silver nitrate produces smaller particles. The color is lighter because the silver nanoparticles are smaller.
• Dried sample: We see a lot more silver nitrate on the edges and corners.
• Evidence of wasting less silver nitrate:
• From the reading and prior knowledge: I added excess tannin.
• Test tube: Excess tannin produces larger particles. The color is darker because the nanoparticles are larger.
• Dried sample: There is no visible silver nitrate. There might be a lot of visible tannin. 
• Evidence of smaller nanoparticles
• From the reading and prior knowledge: The reaction is slower.
• Test tube: The color is lighter.
• Dried sample: The dendrites are thinner but the amount of silver is the same. The sheet of silver is smoother and thinner.
• Evidence of larger nanoparticles:
• From the reading and prior knowledge: The reaction is faster.
• Test tube: The color is darker.
• Dried sample: The sheet of silver is less smooth, grainier. There are fewer dendrites and more thick clumps of silver.

chemical reaction: A process that leads to the chemical transformation of one set of chemical substances to another. Oxidation is a type of chemical reaction.

dendrite: A characteristic, tree-like structure of crystals that grows when molten metal freezes.

Le Chatelier’s principle: Used to predict the effect of a change in conditions when a substance is subjected to a change in concentration, temperature, volume, or pressure; also known as the equilibrium law.

limiting reactant: A substance that is totally consumed when a chemical reaction is complete.

nanoparticle: Particles that measure between 1 and 100 nanometers (nm) in size.

oxidation : The loss of electrons during a reaction by a molecule, atom, or ion.

precipitant: A new solid substance formed from a solution.

product: The substances produced after a chemical reaction.

reactant: The substances that participate in a chemical reaction.

redox reaction: Short for a chemical reaction that includes reduction (red-) and oxidation (-ox) of reactants.

reduction: The gain of electrons during a reaction by a molecule, atom, or ion.

silver nanoparticle: Particles of silver that measure between 1 and 100 nanometers in size; composed largely of silver oxide.

silver nitrate: The substance AgNO3, composed of a silver ion and a nitrate ion.

single replacement reaction: A reaction by which one or more elements replace another element in a compound.

soluble: The ability for a substance to dissolve in water.

tannin: A class of astringent, organic molecules that bind to and precipitate proteins and various other organic compounds. One tannin is tannic acid which has the chemical formula C76H52O46.

Activity Embedded Assessment

Student Workbook: Have students work through the Student Workbook . Sections 2.0, 2.1, 4.0, 6.0, 8.0, and 10.0 all provide opportunities for embedded assessment. 

Post-Activity Assessment

Final Recommendation: Section 10.1 provides a framework where the students can act like a chemical engineer and present their final recommendation for improving the manufacturing process building silver nanoparticles.

Safety Issues

The activity requires glassware and dilute sodium hydroxide. Both require goggles and closed-toes shoes.  Enforce that “nothing in this lab is safe to consume” because some people use silver nitrate and silver nanoparticles as nutrition supplements. 

The tannin solution is weak or not reacting well

Try using hotter water, steeping the tea for a longer period of time, or breaking the tea up into smaller pieces; using more tea while brewing also produces more tannins. 

I want to eliminate the brown tint of the tea

Some substances that make the tea brown can be filtered out using vacuum filtration with micron filters – this may reduce the brown tint if you have access to them.  Additional filtering with medium speed funnel filters provides no benefit. 

Pu’erh tea actually is not required; any substance that is soluble and reduces silver works. Pu’erh tea just contains a lot of tannins. Tannins are a class of large molecules that have a lot of phenol groups. Phenol groups reduce silver and the large size of the tannins limit the size of the silver nanoparticles formed. You may use phenols extracted from fruit and leaves to produce the same results, which is referred to as “green” silver nanoparticle production.  Other phenols may not have a brown tint. 

Using more dilute tea also works but the reaction rate is slower. You would have to leave the solution in test tube D covered overnight.

There is a brown/black substance that covers the dried silver – how can I remove it so I can see the silver underneath?

The brown material from the tannins is not soluble in either ethanol or hot DI water. Mechanical removal will also remove the silver nanoparticles underneath.

Can I use a drying oven to speed things up?

Yes and no. The normal reaction takes hours. Using a drying oven soon after class will produce a lot less silver and leave a lot more silver nitrate because the reaction did not go to completion. Using a drying oven the next morning is a good idea if the sample are not completely dry.

I see threads in the samples

Those may be small airborne fibers that get caught in the sample; some might even get silver plated. To counter this effect, you can cover the petri dishes.

I want to change the concentration of the silver nitrate solution or tannins.

About 1 drop of 0.4M Silver nitrate reacts with about 1 drop of undiluted Pu’reh tea.

I want to use hydrochloric acid or sulfuric acid

Both 0.1M HCl and H 2 SO 4 worked as well as distilled vinegar.  HCl, H 2 SO 4 , and vinegar produce silver chloride, silver sulfate, and silver acetate respectively. All are partly soluble and reduce like silver nitrate. 

When using sodium hydroxide I see light brown crystal nodules

That substance is silver hydroxide. In this case, the experiment may have had inadequate tannin concentration or chemical reaction time.

• Students could perform the inquiry section with a range of samples. Students could examine the effects of adding 0, 1, 2, 3, and 4 drops of excess tannin in five different samples.
• Students could collect all of the results from each group, and could then find patterns in multiple outcomes, refine the process to optimize the production of nanoparticles, and repeat the experiment with the refined process.
• Students could expand on the reduction of silver by metals other than copper, such as iron.  Students could develop some of the activity series of metals.  If a metal reduces silver nitrate it is more active than silver metal.
• Students could explore Mie scattering, Rayleigh scattering and Willis-Tyndall scattering.  Students could make connections between their lab observations and light scattering principles and determine which type of scattering is occurring.
• Students could use redox titration to determine the strength of the tannins reduction potential. Dilute a sample of the tannins, add iodine and starch as indicators then titrate with hydrogen peroxide or some other oxidizing solution.
• For lower grades, students could create their own phenols for reducing silver.  Some could boil red and green apple sand some plant leaves in water to see which extracts reduce silver.  Use fruits and leaves that contain many flavonoids and antioxidants. The lab could consist of which fruits have the most antioxidants – they produce the most silver nanoparticles when mixed with silver nitrate.
• For higher grades, students can explore it as single replacement and redox reactions. They could balance the equations, use molarity, and apply stoichiometry to determine percent yield.
• For higher grades, students could mathematically apply Le Chatelier’s principle to predict changes in silver nanoparticle production before they attempt them.

Student teams conduct an experiment that uses gold nanoparticles as sensors of chemical agents to determine which of four sports drinks has the most electrolytes. Using some basic chemistry and physics principles, students develop a conceptual understanding of how gold nanoparticles function.

Loo, Yuet Ying et al. “Synthesis of Silver Nanoparticles by Using Tea Leaf Extract from  Camellia Sinensis .”  International Journal of Nanomedicine  7 (2012): 4263–4267.  PMC . Web. 6 Jan. 2018.

Tippayawat, Patcharaporn et al. “Green Synthesis of Silver Nanoparticles in Aloe Vera Plant Extract Prepared by a Hydrothermal Method and Their Synergistic Antibacterial Activity.” Ed. Maria Rosaria Corbo.  PeerJ  4 (2016): e2589.  PMC . Web. 6 Jan. 2018.

Zainal Abidin Ali, Rosiyah Yahya, Shamala Devi Sekaran, and R. Puteh, “Green Synthesis of Silver Nanoparticles Using Apple Extract and Its Antibacterial Properties,” Advances in Materials Science and Engineering, vol. 2016, Article ID 4102196, 6 pages, 2016. doi:10.1155/2016/4102196

Contributors

Supporting program, acknowledgements.

This curriculum was based upon work supported by the National Science Foundation under Rice University Engineering Research Center for Nanotechnology Enabled Water Treatment Systems (NEWT) RET grant no.1449500. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.

Special thanks to Dr. Shahnawaz Sinha, Dr. Paul Westerhoff, and Dr. Francois Perreault at Arizona State University for the introduction to the uses and synthesis of silver nanoparticles. Special thanks to Christina Crawford at Rice University for encouraging writing this activity.

Last modified: August 28, 2019