Science on the Road: Visiting the Statue of Liberty & Chemical Reactions

In September, we spent a few days in New York City on the island of Manhattan, the city’s historical birthplace and the economic and center. The borough contains several smaller islands including Liberty Island, Ellis Island (shared with New Jersey), Governors Island, and a few others. We were really looking forward to exploring the area and learning more about the history of the area, specifically the Statue of Liberty.

Science of the Statue of Liberty @EvaVarga.netWe arrived in Manhattan via Amtrak train from Boston in the early afternoon. We thereby opted to take in the Statue of Liberty and Ellis Island the following day when we could arrive early and board the first cruise boat. This turned out to be a wise decision as the queue upon our return to the main island was very long.

We grabbed a quick bite at the deli just outside the Courtyard Marriott on 40th where we are staying then hopped the green line express to Bowling Green. Here, we walked the short distance to the boarding area.

We immediately made our way to the National Park Visitor Center after we disembarked. Here we stamped our Park Passport Books and inquired about guided tours. We were in luck in that the first tour would begin in just 20 minutes. We took a few candid photos (Geneva pulled out her sketch book) as we waited.

As we planned to spend all our time in this area, we opted to purchase the New York CityPASS as the majority of the attractions were in this general area. In addition to Statue of Liberty and Ellis Island cruise, the pass provided us with tickets to each of the following attractions:

  • Statue of Liberty & Ellis Island
  • The Empire State Building
  • American Museum of Natural History
  • The Metropolitan Museum of Art
  • Guggenheim Museum 
  • 9/11 Memorial & Museum   

 

Science & Art of Liberty Island and the Statue of Liberty @EvaVarga.netVisiting the Statue of Liberty & Liberty Island

Liberty Island Tour

The group that gathered for the guided tour of Liberty Island was small and thereby very intimate. I am surprised more people don’t take advantage of this opportunity – they are so very informative and best of all, FREE!

As we listened to the park ranger, we learned the idea of gifting the United States with a monument was first proposed in 1865 by Frenchman Edouard de Laboulaye. Sculptor Frederic Auguste Bartholdi was commissioned to design a sculpture ten years later, with a goal of completing the work in 1876 to commemorate the centennial of the American Declaration of Independence.

As a joint venture between the two nations, it was agreed that the American people were to build the pedestal (carved in granite, the pedestal was designed by architect Richard Morris Hunt in 1884), and the French people were responsible for the Statue and its assembly here in the United States.

In France, public fees, various forms of entertainment, and a lottery were among the methods used to raise funds for the project. In the United States, theatrical events, art exhibitions, auctions and prizefights assisted in financing the construction.

Poet Emma Lazarus wrote her famous sonnet “The New Colossus” in 1883 for the art and literary auction to raise funds for the Statue’s pedestal.

Not like the brazen giant of Greek fame,
With conquering limbs astride from land to land;
Here at our sea-washed, sunset gates shall stand
A mighty woman with a torch, whose flame
Is the imprisoned lightning, and her name
Mother of Exiles. From her beacon-hand
Glows world-wide welcome; her mild eyes command
The air-bridged harbor that twin cities frame.
“Keep, ancient lands, your storied pomp!” cries she
With silent lips. “Give me your tired, your poor,
Your huddled masses yearning to breathe free,
The wretched refuse of your teeming shore.
Send these, the homeless, tempest-tost to me,
I lift my lamp beside the golden door!”
 – Emma Lazarus

Science & History of the Statue of Liberty @EvaVarga.netCentennial Gift 10 Years Late

Financing for the pedestal was completed in August 1885, and pedestal construction was finished in April 1886. The Statue was completed in France in July 1884 and arrived in New York Harbor in June 1885 onboard the French frigate “Isere.”

In transit, the Statue was reduced to 350 individual pieces and packed in 214 crates. The Statue was reassembled on her new pedestal in four months’ time. On October 28, 1886, President Grover Cleveland oversaw the dedication of the Statue of Liberty in front of thousands of spectators.

Homage to the Statue of Liberty Supporters

On Liberty Island, there are several small sculptures commemorating several of the key supporters of the Statue of Liberty gift. I really enjoyed hearing the personal triumphs that made it all possible.

  • Edouard de Laboulaye ~ The “Father of the Statue of Liberty.” He provided the idea that would become the Statue.
  • Frederic Auguste Bartholdi ~ The French artist and sculptor who designed the Statue of Liberty Enlightening the World.
  • Alexandre-Gustave Eiffel ~ The architect and engineer who designed the Statue’s internal support.
  • Emma Lazarus ~ The poetess who wrote “The New Colossus” to help raise money for the pedestal’s construction.
  • Joseph Pulitzer ~ The newspaper publisher who helped raise the money needed to complete the pedestal’s construction.

One of the things I overheard many of the young visitors ask as we walked about the island was, “Why is it green?” I knew that when I returned home, this was a concept I wanted to revisit with my children.

Bring it Home ~ Oxidation Reduction Reactions

Why is the Statue of Liberty Blue-Green?

Begin by showing students photographs of the Statue of Liberty.  Ask students to describe the color. Students usually give the right answer: that it is blue or aquamarine (blue-green). Now ask them why it is this color. Students generally have no clue.

Explain that the color is due to the oxidation of copper. Next, show them a piece of rusted metal and point out that the red color of rust is caused by the oxidation of iron.

Science of Oxidation and the Statue of Liberty @EvaVarga.netOxidation Explained with Chemical Equations

Chemical reactions can be divided into two classes: redox (reduction-oxidation) reactions and non-redox reactions based on whether electron transfer process is involved or not. A redox reaction consists of two half reactions: a reductive half in which a reactant accepts electrons and an oxidative half in which a reactant donates electrons.

2Cu + O2 → Cu2O

The nature of a redox reaction is that one reactant donates its electrons to the other reagent. For example, in the oxidation of copper by oxygen, copper atoms donate electrons to an oxygen molecule so copper is oxidized while oxygen is reduced.

The Statue of Liberty gets its blue-green color from patina formed on its copper surface mainly through oxidation along with several other chemical reactions. The main constituent of patina contains a mixture of 3 compounds: Cu4SO4(OH)6 in green; Cu2CO3(OH)2 in green; and Cu3(CO3)2(OH)2 in blue. The following reactions are involved.

2Cu2O + O2 → 4CuO

Cu + S → 4CuS 

The oxidation starts with the formation of copper oxide (Cu2O), which is red or pink in color (equation 1), when copper atoms initially react with oxygen molecules in the air. Copper oxide is further oxidized to copper oxide (CuO), which is black in color (equation 2). In the 19th and early 20th century, coal was the major fuel source for American industry and it usually contains sulfur. Thus, the black copper sulfide (CuS) also forms (equation 3).

2CuO + CO2 + H2O → Cu2CO3(OH)2

3CuO + 2CO2 + H2O → Cu3(CO3)2(OH)2

4CuO + SO3 +3H2O → Cu4SO4(OH)6

Over the years, CuO and CuS slowly reacts with carbon dioxide (CO2) and hydroxide ions (OH-) in water from the air to eventually form Cu2CO3(OH)2 (equation 4) , Cu3(CO3)2(OH)2 (equation 5) and Cu4SO4(OH)6 (equation 6), which constitute the patina. The extent of humidity and the level of sulfur-related air pollution have a significant impact on how fast the patina develops, as well as the relative ratio of the three components.

Take it Further

Can you think of another oxidation reduction reaction? Write out the chemical equations to further describe this process.

 

Carl & Gerty Cori Change the Face of Medicine

In brilliant collaboration, Carl and Gerty Cori studied how the body metabolizes glucose and advanced the understanding of how the body produces and stores energy. Their findings were particularly useful in the development of treatments for diabetes. They were awarded the Noble Prize for their discovery of how glycogen (animal starch) – a derivative of glucose – is broken down and resynthesized in the body, for use as a store and source of energy.

cori cycleThe pair were interested in how the body utilizes energy. The couple spent more than three decades exploring how the human body metabolizes glucose. It was known in the 1920s that faulty sugar metabolism could lead to diabetes, and it was also known that insulin kept the disease in check.

The effect of insulin on blood sugar levels had been observed, but scientists did not understand the biochemical mechanism behind insulin’s effect or how carbohydrates were metabolized. In 1929, the couple described what is now known as the Cori cycle; an important part of metabolism. To put it simply, lactic acid forms when we use our muscles, which is then converted into glycogen in the liver. Glycogen, in turn, is converted into glucose, which is absorbed by muscle cells.

The Cori Cycle

cori cycleThe Cori Cycle refers to the metabolic pathway in which lactate produced by anaerobic glycolysis in the muscles moves via the blood stream to the liver where it it is converted to blood glucose and glycogen. High intensity exercise will mostly get it’s energy or ATP from the pathway of the glycolitic system.  Less intense activity will receive its energy or ATP from the aerobic pathway utilizing the Krebs cycle.

When utilizing the glycolitic system, cycle after cycle, lactate will start to build up.  Lactate from the glycolitic system will diffuse from the muscles into the bloodstream.  It will then be transported into the liver.  In the liver it is converted from lactate back to pyruvate back to glucose, which is then available to the muscles again for energy, this is called gluconeogenesis.  The whole process is called the Cori Cycle.

The more you train with high intensity exercise, the more capable the enzymes and transporters become that are needed for the Cori Cycle.  Your liver gets better at using the lactate, not more efficient (it still needs the same amount of ATP to run the Cori Cycle) but it will do the cycle faster.

Gerty Cori Biography

carl & gerty cori Gerty Radnitz was born in Prague in what was then Austria-Hungary. She received her PhD in medicine from the German University of Prague’s Medical School in 1920. It was here that she met fellow classmate, Carl Ferdinand Cori, whom she married later that same year.

The couple moved to Buffalo, New York in 1922 and began researching metabolic mechanisms. As a woman, Gerty Cori was employed on much less favorable terms than her husband and encountered other forms of gender discrimination throughout her career.

The couple moved to Washington University in St. Louis in 1931 after both were offered positions there. When the Coris were hired at Washington University, she received one-tenth Carl’s salary, even though they were equal partners in the laboratory.

Gerty and her husband continued to investigate how glycogen is broken down into glucose and in 1939 were able to both identify the enzyme that initiates the decomposition and also to use the process to create glycogen in a test tube.

She became full professor in 1947, the same year that she and Carl were awarded the Nobel Prize “for their discovery of the course of the catalytic conversion of glycogen.” She was the first American woman to win the Nobel Prize in Science.

Around this time Gerty was diagnosed with myelosclerosis, a disease of the bone marrow. She died in 1957 at the age of 61.

Bring it Home

Try this hands-on lab from Amy Brown Science to discover The Use of Glucose in Cellular Respiration

Enjoy the Carl and Gerty Cori and Carbohydrate Metabolism commemorative booklet produced by the National Historic Chemical Landmarks program of the American Chemical Society in 2004.

Read about the dip-and-read test strips developed by Helen Free and her husband, Al. Originally designed to test for glucose in urine, the test strips were such an advance that researchers have since combined 10 urine tests to check for ailments like liver failure, urinary tract infections, and others—onto one plastic stick.

Learn more about our digestive system with these hands-on enzyme labs.

Investigate What Types of Food Contain Starch and Protein?

Building Macromolecule is a paper-scissors-tape activity used to help students envision the process of synthesis, building macromolecules out of smaller subunits.

Science Milestones

Visit my Science Milestones page to learn more about scientists whose discoveries and advancements have made a significant difference in our lives or who have advanced our understanding of the world around us.

Interested in learning about others who were born in the month of August? Hop over to Birthday Lessons in August to read posts by other iHomeschool Network bloggers.

 

Rosalind Franklin: The Unsung Hero of DNA Structure

Rosalind Franklin, a scientist whose role in the discovery of DNA structure in 1953 has been forgotten by many, has a chance to be immortalized in a feature film. Throughout her career she faced sexism at nearly every turn. She also happened to be Jewish, which heightened the prejudice against her. Her name may soon be on the tips of everyone’s tongue and her role in the discovery of DNA Structure known to all. Entertainment One has acquired the script to Exposure, her life story.

In 1962 James Watson, Francis Crick, and Maurice Wilkins jointly received the Nobel Prize in physiology or medicine for their 1953 determination of the structure of deoxyribonucleic acid (DNA). Rosalind Franklin (1920–1958), a colleague of Wilkins, died of cancer at the age of 37, and was thereby not equally honored because the Nobel Prize can only be shared by three scientists. It was her work in X-ray crystallography, however, that proved critical to the correct solution to DNA structure.

Unsung Hero of DNA Structure @EvaVarga.netWhat is DNA?  

DNA is the material embedded in the cells of all living organisms that carries the genetic coding that determines how a living thing will look and function. It is found in the nucleus of each cell and is unique to every individual – whether human, mountain lion, or butterfly. Its full name is deoxyribonucleic acid, which can be complicated to say, so we usually refer to it as DNA for short.

DNA is so tiny that it can not be seen unless we use a very powerful microscope. If we could see it we would see that it looks like a twisted ladder, which scientist refer to as the double helix. Each rung or step on the DNA ladder is composed of two letters.

There are only 4 letters — A,T,G, and C — and each has a unique puzzle-like shape. This means that A and T fit together to form a rung on the ladder and G and C fit together to form another rung on the ladder.

As we read the DNA ladder, the letters combine to form 3-letter words called codons. Then, these codons combine to form sentences that we call genes. These genes are the basis for your chromosomes, which give your body a blueprint or set of instructions for life.

Every human has 23 pairs of these DNA chromosomes that determine what we look like and how to perform. We get one set of chromosomes from our mother and one set from our father. Our chromosomes determine whether our eyes will be blue or brown, what color our skin and hair will be, whether we will be a boy or girl and so much more.

The Structure of DNA @EvaVarga.net

Building a Cardboard Safari DNA Double Helix Puzzle

Discovering DNA Structure

Inspired by Linus Pauling’s success in working with molecular models, James Watson and Francis Crick rapidly put together several models of DNA and attempted to incorporate all the evidence they could gather. Franklin’s excellent X-ray photographs, to which they had gained access without her permission, were critical to the correct solution. Along with Wilkins, Franklin’s partner, the four scientists announced the structure of DNA in articles that appeared together in the same issue of Nature.

After the publication, they moved on to different projects. Franklin went to Birkbeck College, London. Before her untimely death from cancer, she made important contributions to the X-ray crystallographic analysis of the structure of the tobacco mosaic virus, a landmark in the field. By the end of her life, she had become friends with Francis Crick and his wife and had moved her laboratory to Cambridge, where she undertook work on the poliovirus.

Biography

Rosalind Franklin @EvaVarga.netRosalind Franklin was born July 25, 1920 to a Jewish family in London, England. Educated at private schools in London, she studied natural sciences at Newnham College, Cambridge, from where she graduated in 1941. She joined the University of Cambridge where she earned a research fellowship in a physical chemistry laboratory under Ronald George Wreyford Norrish. The British Coal Utilisation Research Association offered her a research position in 1942, and started her work on coals. This helped her earn a PhD in 1945.

In 1947, she went to Paris as a chercheur (post-doctoral researcher) under Jacques Mering at the Laboratoire Central des Services Chimiques de l’Etat, where she became an accomplished X-ray crystallographer. She returned to London in 1951 and became a research associate at King’s College. She was compelled to move to Birkbeck College after two years, however, owing to disagreeable clashes with her director and more so with her colleague Maurice Wilkins. At Birkbeck, J. D. Bernal, chair of the physics department, offered her a separate research team. She died on April 16, 1958 at the age of 37 of ovarian cancer.

Bring it Home

Build a model of the DNA Double Helix with the Cardboard Safari Puzzle

Create a model of DNA with colorful Wiki-Sticks

Extract DNA from Strawberries in this great lab from Marci at the Homeschool Scientist

Explore the DNA Teaching Resources from Karyn at Teach Beside Me

Challenge your students with this Transcription / Translation Lab Activity 

Download the DNA & RNA Protein Synthesis Interactive Notebook Resources from Science with Amy

Make these cool DNA Sequence Bracelets

Watch this fabulous NOVA documentary on PBS, The Secret of Photo 51

Science Milestones

Unlocking the Secrets of Invisible Ink

Have You Ever Wondered …

How does invisible ink work?

What common household substances can be used to make invisible ink?

What things can you do to reveal a message written in invisible ink?

Steganography is the practice of concealing a file, message, image, or video within another. The use of invisible inks is one of the earliest known examples of steganography. Invisible ink today is mostly considered child’s play, but in the not too distant past, its use and the recipes were considered classified government information.

Using the suggested inks and reagents provided here, write a secret message to a friend. Then get creative and see how many kinds of invisible ink you can find.Unlocking the Secrets of Invisible Ink @EvaVarga.net

Types of Invisible Inks

There are two categories into which invisible inks fall ~ organic fluids and sympathetic inks. You can find many heat-activated invisible inks right inside your kitchen. Another type of invisible ink is chemically activated. Read on to learn more about each.

Organic or Heat-Activated Invisible Inks

Organic fluids consist of the natural methods your likely already familiar: lemon juice, vinegar, milk, or onion juice, to name a few. These organic invisible inks can be revealed through heat, such as with fire, irons, or light bulbs.

The organic fluids alter the fibers of the paper so that the secret writing has a lower burn temperature and turns brown faster than the surrounding paper when exposed to heat. To activate or develop the ink, simply iron the paper, set it on a radiator, place it in an oven (set lower than 450° F), or hold it up to a hot light bulb.

  • any acidic fruit juice (e.g., lemon, apple, or orange juice)
  • onion juice
  • sodium bicarbonate NaHCOsolution (baking soda)
  • vinegar
  • white wine
  • diluted cola
  • milk
  • soapy water
  • sucrose solution (table sugar)
  • bodily fluids

solution is a homogeneous mixture composed of two or more substances. In such a mixture, a solute (baking soda or sugar) is a substance dissolved in another substance, known as a solvent (water).

Inquiry Science :: What other organic inks can you find? Which kind shows up best? Which kind lasts longest?

Unlocking the Secrets of Invisible Ink @EvaVarga.net

Sympathetic Inks

Sympathetic inks contain one or more chemicals and require the application of a specific “reagent” to be activated, such as another chemical or a mixture of chemicals. Most of these inks work using pH indicators, requiring the recipient to paint or spray a suspected message with a base (like sodium carbonate Na₂CO₃ or washing soda solution) or an acid (like lemon juice). Some of these inks will reveal their message when heated.

  • lemon juice, activated by iodine solution
  • starch (e.g., corn starch or potato starch), activated by iodine solution
  • vinegar or dilute acetic acid CH3COOH, activated by red cabbage water
  • ammonia NH3, activated by red cabbage water
  • sodium bicarbonate NaHCO3 (baking soda), activated by grape juice
  • sodium chloride NaCl (table salt), activated by silver nitrate
  • phenolphthalein (pH indicator), activated by ammonia fumes or sodium carbonate Na₂CO₃ (or another base)
  • lead nitrate, activated by sodium iodide
  • iron sulfate, activated by sodium carbonate, sodium sulfide, or potassium ferricyanide

CAUTION: Some of the chemicals suggested here can be hazardous if misused. Always use caution when working with chemicals. Read the information on the chemical label before you start, and always wear protective safety equipment such as goggles, gloves, and aprons. Adult supervision required.

Ultraviolet Light Activated Invisible Inks

Most of the inks that become visible when you shine an ultraviolet or black light on them will also become visible if you heat the paper. Here are are few ‘glow-in-the-dark’ ideas to try:

  • dilute laundry detergent (the bluing agent glows)
  • tonic water (quinine glows)
  • vitamin B-12 dissolved in vinegar

The History of Invisible Ink

The history of invisible ink is incredibly fascinating and swings wildly between high-tech methods and the humblest of approaches. Invisible ink was a key method for spy communications throughout history. Prisoners, Lovers, and Spies is an historical account of invisible ink and the secret communications revealed through thrilling stories about scoundrels, heroes, and their ingenious methods for concealing messages.

The Catholic Mary, Queen of Scots, kept under luxurious house arrest for eighteen years by her Protestant cousin Elizabeth I, advised correspondents to write to her employing two commonly used substances: alum (hydrated potassium aluminum sulfate) or nutgall (the tannic acid secreted in swellings generated by parasitic wasps colonizing oak trees). Letters written in alum required the recipient to soak the paper in water, while nutgall needed a solution of ferrous sulphate as a reagent.

During World War II, chemist Linus Pauling worked on an unusual wartime project, formulating new kinds of invisible ink that would resist all known reagents. Pauling and his colleagues experimented with invisible inks made from pneumococcus bacteria (an inert strain so as not to spread pneumonia). The ink-ified microbe would react to an antibody, and then become visible once dipped in a dye solution. However, the ink never passed the experimental stage.

Visit The Art of Manliness for a more detailed look at how invisible inks have been used in espionage and naval intelligence.

Make Your Own BioPlastics

bio plasticsPlastics play an important role in our lives.  Plastics are used to manufacture many everyday items and have significantly reduced the use of glass.  Some plastics are very durable and make things like furniture and appliances.  Other plastics make items such as diapers, trash bags, cups, utensils and medical devices.  The largest amount of plastic is used to make containers and packaging for items such as soft drink bottles, lids, shampoo bottles, etc. Common plastic is made from petroleum, a fossil fuel which is nonrenewable.

Nonrenewable resources are made naturally by the earth, but do not renew themselves fast enough to be able to count on having the resource for an indefinite period time.  Some resources are considered non-renewable because our access to the resource is limited.  For example, glass and metal are non-renewable resources.  The elements and minerals used to make glass and metal are found in the structure of the earth’s crust, however we are limited to what we can access through mining.

Renewable resources are either naturally reproduced at a sustainable rate or they can be produced in agriculture at a rate equivalent to the demand or need.  For example, corn can be used for ethanol fuel and to produce corn oil.  Corn is a renewable resource.

DIYBioPlasticsBioplastics are a type of plastic made from renewable, biological materials like starches, cellulose, oils or proteins. They generally contain little to no petroleum and therefore are usually biodegradable. When bioplastics are exposed to the environment (sunlight, heat, water, microorganisms) they breakdown into non-toxic compounds like carbon dioxide and water. Additionally, unlike petroleum-based plastics, bioplastics are made from renewable resources. These resources are typically agricultural byproducts, like cornstarch and potato starch, tapioca starch and casein (milk protein).

Biodegradable: refers to material capable of breaking down into harmless products through the action of living organisms or natural processes

Byproducts: in agriculture refers to secondary products created from a crop. For example, corn starch is a byproduct of corn

Make Your Own BioPlastics

Materials

  • Plant based oils (Corn Oil, Sesame Oil, Vegetable Oil)
  • Cornstarch
  • Water
  • Food coloring
  • Measuring spoons
  • Eyedropper (optional)
  • 1 Ziploc bag per student
  • Access to a microwave oven

BioPlasticsProcedure

  1. Place the following ingredients in a plastic bag: 1 tablespoon of cornstarch, 2 drops of oil, 1 tablespoon of water, and 2 drops of food coloring.
  2. Seal the bag and gently mix the cornstarch mixture by rubbing the outside of the bag with your fingers until combined.
  3. Open the bag slightly, making sure it can vent. Place the bag in a microwave oven on high for 20-25 seconds.
  4. Carefully remove the bag from the microwave and let it cool for a few minutes. While it is still warm, students can try to form their plastic into a ball. Observe what it does.
  5. Ask them to describe their plastic; did it turn out differently than others? Does the type of oil you used affect the bioplastic? Have the students name three things they could make with bioplastic.

Take it Further

I’m committed to sharing activities and resources for teaching science in your homeschool. I believe it is helpful to see that science isn’t scary and it doesn’t require special curriculum. Here are a few resources that you can use to further your study of plastics and renewable vs. nonrenewable resources.

Watch the 3-minute How Stuff Works video clip about Corn Plastic.

In this hands-on, inquiry based Plastics Lab Activity, students investigate whether all plastics the same? How are they different?

Polymers Are Cool ~ Experiment with different polymers, large molecules composed of many repeated subunits, with these 3 great recipes.

As plastics are not biodegradable, learn how you can make a difference in encouraging others to reduce our use of plastics. The volunteers at Washed Ashore inspired us to create a Bottle Cap Mural to help spread the word of the harm done to our oceans by plastics.

 

Polymers Are Cool: 3 Recipes for Middle School

Chemistry is great for making many useful products. It’s also good for making stuff that’s just fun to play with. One of my favorite chemistry units is on polymers.

A polymer is a large molecule, or macromolecule, composed of many repeated subunits. In other words, they are made up of many, many molecules all strung together to form really long chains.

Polymers Are Cool: 3 Polymer Recipes for Middle School @EvaVarga.netIn Greek, Poly- means “many” and -mer means “part” or “segment”.  Mono means “one”. So, monomers are the individual molecules that can join together to make a long polymer chain.

A single polymer molecule is made out of hundreds of thousands (or even millions!) of monomers. Not all molecules can link up in this way to form polymers, however.

The atoms that make up a polymer chain essentially line up and repeat all along the length of the polymer chain. For example, look at polypropylene:


Polypropylene is made up of just two carbon atoms repeated over and over again. One carbon atom has two hydrogen atoms attached to it, and the other carbon atom has one hydrogen atom and one pendant methyl group (CH3).

In this example, the pendant group hangs from the carbon atom in the chain backbone. As you can see from the example, pendant groups usually repeat along the length of the chain as well.

But enough of the mumbo jumbo. Let’s get to the fun stuff. What is better than reading about chemistry? Doing the labs, of course!  Here are three tried and true recipes for polymers you can use in the classroom.

Polymer Recipes ~ Get Messy!

Basic Polymer Putty

This is a fun and easy polymer to make (and the one featured in the photographs).

Materials

  • Elmer’s white glue
  • Borax (find in the laundry detergent aisle of the store)
  • Water
  • Two bowls
  • Food coloring (just for fun)

Procedure

  1. In one bowl mix 1/2 cup (4 oz) glue and 1/2 cup water. Add food coloring if you want colored slime.
  2. In the other bowl, slowly mix borax into 1 cup of water until the borax will no longer dissolve (this is a saturated solution).
  3. Add the glue mixture to the borax solution, stirring slowly.
  4. The slime will begin to form immediately; stir as much as you can, then dig in and knead it with your hands until it gets less sticky.  Don’t worry about any leftover water in the bowl; just pour it out.

The glue has an ingredient called polyvinyl acetate, which is a liquid polymer. The borax links the polyvinyl acetate molecules to each other, creating one large, flexible polymer. It will get stiffer and more like putty the more you play with it.

Store it in a plastic bag in the fridge, to keep it from growing mold.

polymer recipesA Firmer Polymer

This recipe makes a firmer, dryer slime that will even bounce if it is kneaded enough.

  1. Mix 4 tsp. (20 ml) water with 5 tsp. (25 ml) Elmer’s or other white glue in a small bowl.
  2. Add 1 tsp. (5 ml) talcum powder and stir until thoroughly mixed.
  3. Add 1 or 2 tsp. (5 or 10 ml) saturated borax and water solution. Stir four a few minutes.
  4. Remove the glob from the bowl and stirrer. Knead it for a while and it will become drier.

You will probably need to wipe off some of the excess moisture from your hands with a paper towel from time to time. Don’t be tempted to wipe the glob with a paper towel as it will only stick. You can add a little talcum to the surface if you are having trouble getting it dry enough. Store in a zip lock in the fridge.

plastics lab activityTake a closer look at plastics & polymers

Super Slime

This slime is similar to the one above, but creates a less rubbery and more transparent slime. This is the real gooey deal! (This slime is non-toxic, but still keep these chemicals away from unsupervised children and wash your hands after playing with the slime.)

Materials

  • Polyvinyl Alcohol (PVA)
  • Borax
  • Water
  • Graduated cylinder or measuring cups and spoons
  • Food coloring (just for fun)

Procedure

  1. Make a 4% solution of polyvinyl alcohol: Stir 1.5 teaspoons (approx. 4g) of PVA into 1/2 C (approx 100 ml) of water in a large microwave-safe bowl. Cover the bowl and microwave for 1 minute, then stir. Microwave another 30 seconds and stir. Continue until all the PVA is dissolved. A slight film may have formed on top; you can remove that with a spoon. You can add food coloring if you want colored slime. Allow the solution to cool.
  2. Make a 4% borax solution by stirring a little less than 2 teaspoons (approx. 4g) of Borax into 1/2 cup of water.
  3. Pour the cooled PVA solution into a ziplock bag and add 2 teaspoons (10ml) of the borax solution.
  4. Zip the bag and knead it until the chemicals are mixed into slime. Then scoop it out and play with it.

While water is a liquid made up of individual H2O molecules, polyvinyl alcohol is formed of long chains of connected molecules, making it a liquid polymer. The borax acts as a “cross-linker,” linking the individual PVA chains to each other. The borax molecules form hydrogen bonds with molecules present in the PVA chains. The partial positive charge of hydrogen atoms attracts the partial negative charge of oxygen atoms. Since hydrogen bonds are weak, they can break and reform as you play with the slime or let it ooze on a flat surface.

Your slime will last for a while if you seal it in a plastic bag and keep it in the fridge.

Misconceptions in Chemistry @EvaVarga.net

Learn how to dispel children’s Misconceptions in Chemistry & Physics.

Helpful Hints for Success with Polymers

Gel type glues

Over the past few years several brands of gel type glues have been introduced. Most of these make excellent slimes which are very elastic and have a nice color and consistency. I have personally experimented with Elmer’s School Glue Gel, but there are several similar products available from other manufacturers. Try substituting a gel glue in the Basic Polymer recipe, above.

Slime overly sticky or runny?

If your white glue or gel glue based slime is too sticky or runny, first try kneading it for a while. Working it in your hands will help to mix things up better, as well as remove some of the moisture. If it is still not quite right, mix 1 part borax with 10 parts water. Dunk the slime into this solution, remove and knead.

Precautions

  • Polymers can wreak havoc with plumbing, so don’t throw them down the drain.
  • Always wear a mask when mixing PVA.
  • Use distilled water for all solutions for best results.
  • Keep polymers away from anything they could damage. They can dry into fabric and the dyes can stain surfaces, including wood.
  • Supervise small children when playing with polymers so they do not ingest any.
  • Some people are allergic to Borax powder. Wearing rubber gloves when mixing should help.
  • Polymers using Borax solutions work best if you pour the Borax solution into the other solution, rather than the other way around. Coloring should be added before the Borax.
  • Use metric measurements whenever possible. This will make it simpler to experiment with different concentrations and ratios.

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