The Chemistry of Everyday Things: Olympic Gold, Silver, and Bronze

Welcome to my first of many posts to come! Let me start by introducing myself. My name is Sherri Rukes and I am the American Association of Chemistry Teachers (AACT) High School Ambassador for the 2016 – 2017 school year. I am a high school teacher in the suburbs of what people around me call the ‘Chicagoland area.’ I have taught chemistry (honors, regular, and now AP), physics (regular and honors) and physical science for the past 21 years. Currently I am teaching AP Chemistry in a program that I’ve personally grown from 14-18 students, to now over 60 students on average per year.

As a high school chemistry teacher (no matter what level I teach), my students think that I eat, work, and sleep chemistry. Well, my students are somewhat correct. Even though I love other things—my dog, the Chicago Bears, Blackhawks, and the beloved Cubs—I do eat, work, and sleep chemistry. In everything that I do, I think about the connection to chemistry in the hope that my students will see my passion and love for chemistry. As I continue with this blog series over the course of the year, I am going to write about the chemistry of my interests, students’ interests, and the chemistry of everyday things. The goals connected to my blog are: to inspire other teachers to relate what is taught in their classroom to the chemistry all around us; encourage students and society to appreciate chemistry; and to provide ideas about connecting the world around us to the chemistry classroom.

As my summer is winding down and I am getting ready for back to school, I started to think about all of the chemistry that is involved in the success of the Summer Olympics in Rio de Janeiro. The most popular item that comes to mind is the medals, so this blog post will focus on the materials used to create the gold, silver, and bronze medals. We’ll examine two questions: “What are the medal compositions?” and “What is the monetary value of each medal?” Let’s focus on the 2016 Rio Summer Olympics considering they are fresh in our minds.

Sustainability

Protecting the world’s environment, the Rio Olympics produced medals with sustainability in mind. For example the gold was extracted without the use of mercury, from the mining all the way to the end design of the medal. According to the Rio committee, the metals used were recycled. The silver metal is roughly 93% pure, and comes from recycled raw silver of leftover mirrors, solder and X-ray plates. In the bronze medals, 40% of the copper used actually came from the Brazil Mint itself. Even the ribbons that the medals hang on are made with 50% recycled PETE, an acronym for Polyethylene terephthalate, plastic which water and soda pop bottles are made from.

Composition and cost

The dimensions of the medals are roughly 850 mm in diameter and 6 mm -11 mm in thickness. The mass of the medals is about 500 grams. If the gold medal was truly solid gold it would be worth over $39,000 USD as of the June 2016 markets. However, the gold medal is not solid gold. It is a mixture of silver, copper and gold. The mixture is 91% silver, 8% copper and just 1% gold. The gold for the London games was actually electroplated onto the metal. Those medals are worth a little over $500 according to today’s market. The mixture of the silver medal changes the value to $260.00 in today’s market. So this raises the questions: how do these medals compare to the previous Olympics, and were there ever any true gold medals handed out?
Related lesson: More information about making a gold medal can be found in this article, “Are Gold Medals Really Gold?” To teach electroplating, use this easy activity from Flinn Scientific, “Microscale Electroplating Lab.”

• Related lesson
  More information about making a gold medal can be found in this article, “Are Gold Medals Really Gold?” To teach electroplating, use this easy activity from Flinn Scientific, “Microscale Electroplating Lab.”

History of the Olympic medal

The first modern Olympics were held in Athens, Greece in 1896, and gold medals were not awarded to first place. Instead, silver was awarded to the first place victor along with an olive wreath, and the second place finisher received a copper based bronze medal. It wasn’t until the 1904 games when a gold medal was handed out for first place, but it was solid gold. This was used from the 1904 Olympics to the 1912 games. Because the medals were solid gold, they were much smaller than the medals handed out today. After the 1912 Olympics, there was a change in how the medals were made. Due to the strain of resources that began due to the First and Second World Wars, the medals ended up being gold plated. There are now requirements that must be met for the medals used for the games. According to the Olympic committee, gold medals must be made from at least 92.5% silver, and must contain at least 6 grams of gold. All medals–gold, silver or bronze–must be at least 60mm in diameter and 3mm thick. So if the medals from the 1904-1912 Olympics were the same dimensions of the medals today, the cost of the medal would be $22,150.40 USD. That is over 40 times the cost of the gold medal given out today! To put that in perspective, the women’s gymnastics team medals would be worth a whopping $110,572.00 USD. ( You can read more interesting facts about the Olympics here.)

Alloys

Because the size and composition changes from games to games, most of the medals are mixtures called alloys. Alloys have many different applications and can be found in building materials, medical implants, and jewelry. The mixture of the metals used in Olympics medals causes the materials to change their properties. Combining these metals together brings the value of the piece to go down, but makes the medal stronger and harder. (More information about alloys in coins, can be found in this Chemmatters article.)

Just like typical mixtures, alloys can be either homogeneous or heterogeneous. If the composition of the mixture contains components that are uniformly mixed within the substance than they are homogeneous. There are two main groups of homogeneous alloys: substitutional and interstitial alloy. A substitutional alloy is one in which the atoms are taking up the space where the “host” metal would normally be found. This is usually done by solid state diffusion. Substitutional alloys combine two or more atoms that are similar in size. The difference in atomic radii of the combining metals must be within 15%. Another important characteristic of substitutional alloys is that the metals need to have similar chemical bonding properties. The metals that suits these criteria are the d block metals on the periodic table. They are all very close in size going across their respective rows and have similar properties.

Alternately, if atoms occupy the spaces in between the atoms of the “host” metal, then the alloy is known as an interstitial alloy. Interstitial alloys need one small radii atom and one large radii atom. Steel is an example of an interstitial alloy where the carbon migrates into the empty spaces of the iron metal host. However, an alloy such as stainless steel is both interstitial, as well as, substitutional. The carbon is in the empty spaces making it interstitial, but the nickel and chromium atoms take the place of some of the iron in the structure.

Substitutional alloys are much more common than the interstitial alloys, and the first known man-made alloy was bronze– a substitutional alloy. Bronze was made with roughly 70% to 90% copper and the rest tin. This makes the alloy much more durable and harder than 100%copper, which is easy to melt and cast. Historically, bronze was harder than many other building materials, and much more resistance to corrosion.

Monetary value

The largest medals were handed out at the 2012 games. The composition was similar to this year (gold – 1.3%, silver 93% and 6% copper for the gold), but lighter than the medals for the 2016 games. The mass of the gold medal from the 2012 games is 412 grams, and the Rio games is over 500 grams. Because the cost of gold and silver was more expensive during the 2012 London games, the cost of the gold medal at the 2012 games ends up being worth $651 today. The 2106 gold metal is worth $500 (Find more information about Olympic medals.)

Applications in the classroom

So when thinking about when to do the old favorite lab of brassing / alchemy of a penny this year, (Brassing a penny lab activity or Flinn Scientific lab ) think about doing it at the beginning of the school year while the Olympics are fresh in student minds. Ask why copper needs to be added to silver to make it harder. Have them calculate the cost of a medal made out of pure gold ($22,150.40). And ask them to reflect on why the material in a bronze medal is only worth $3.00, but to Olympians it’s priceless.

And consider talking about alloys. Alloys are a great way to connect chemistry to the world around us. They’re found all over the place; buildings with steel (iron and carbon mainly with other metals depending on the use), old amalgam fillings for teeth (alloy of mercury, tin, silver, zinc and copper), and memory wire (NiTinol) used for medical stents, glass frames, and magic tricks (come back to learn more about NiTinol in the future).

I hope this post has given you some ideas to talk about the next time students ask why they need to know chemistry! Continue to relate what the students talk and think about to chemistry. My next blog post will continue to talk about the Olympics, and focus on the advancements in materials athletes use to compete. All throughout this upcoming school year, I will examine the many materials that make up the world and connect them to the subject which I love – CHEMISTRY.

Ms. Sherri Conn Rukes is an AP Chemistry at Libertyville High School in Libertyville, IL. She earned a B.S. in Chemistry, Mathematics and Physics from the University of Illinois in Champaign Urbana and an M.S. in Education from NOVA Southeastern University in Florida. Sherri has done research at Northwestern University in Material Science (from MWNT to art restoration), is a Polymer Ambassador, is a master teacher for ASM and has presented at several NSTA, ACS, and ISTA conferences. You can follow her on Twitter @polychemgirl or @sherrirukes.

Editor’s Note: Sherri currently serves on the AACT governing board as the High School Ambassador. This is her first blog post in a new series for the 2016-17 school year The Chemistry of Everyday Things. Read a new post each month on the AACT blog as Sherri shares resources, news, her perspectives, and more!