Spectroscopy at Home

Hello again from the secret ACS demonstration laboratory! Today, we have a demo video for you to help explain one of the mainstays of analytical chemistry: spectroscopy. Use this demonstration to show how we scientists know if a substance is present in a sample, and how much of that substance is present.

From: metryq.deviantart.com/art/fluorescing-tonic-water-416559283

From: metryq.deviantart.com/art/fluorescing-tonic-water-416559283

To perform this demonstration, you will need:

  • a highlighter (we used the bright yellow Sharpie brand)
  • A bottle of tonic water
  • a purple laser (do NOT point this at anyone’s face!) (We bought ours here)
  • a small glass vial (plastic will do)
  • 3 clear plastic cups
  • water (tap water will do)
  • goggles

Safety Notes:

Although you’re only using household items, you’ll be performing this as a part of a demo show, so you should be wearing your safety goggles. Even if you’re performing this demo by itself, wear your goggles anyway- its a science thing, and we only do science things if safety is addressed.

Also, don’t shine the laser in anyone’s face.

Procedure:

spectroscopy from ACS Undergraduate Programs on Vimeo.

To perform this demo, start by explaining that scientists often need to know what is present in our samples. One of the ways we do this is through the interaction of light and and radiated energy, through a process called spectroscopy.

Experiment 1: Light can show us if a substance is present in a material.

Demonstrate that a laser, shined through a vial of tap water, leaves no trail.  This is because nothing in the tap water fluoresces when hit by the laser.

Take your highlighter, and dip the tip of the highlighter into the water. Demonstrate that now the laser now fluoresces the liquid due to the addition of material from the highlighter.  Explain how, just as the laser reveals the presence of the highlighter, scientists can use other forms of radiant energy to detect certain chemical compounds.

Experiment 2: Light can show us how much of a substance is present in a material.

Start by filling one of the plastic cups with water, one with tonic water, and one with a 1:4 ratio of tonic water to water. Ask your audience to predict which glass will glow the brightest when the laser is shined through it. Show the laser shining in each glass, and explain that the more tonic water is present, the brighter the laser will fluoresce the liquid.  Explain that, using similar techniques, analytical chemists can determine the amount of substances present, such as the amount of chlorine in tap water or the amount of sugar in cola.

Take a look at our video for our take on this. Feel free to comment about how you think it could be done better!

NCW Pictures from Our ACS Student Chapters

National Chemistry Week has come and gone, but we’ll always have the memories, right?  Oh, we’ll also have these great pictures you said we could use!  Got other pictures for us?  Email us and let us know!  We’ll add to this post as we receive your pictures.

Nick L Mole, the CSU-Fresno ACS Student Chapter Mascot, celebrates his 3rd birthday.

Nick L Mole, the CSU-Fresno ACS Student Chapter Mascot, celebrates his 3rd birthday.

There was a pinata at Nick's birthday.  I think our invitation got lost in the mail....

There was a pinata at Nick’s birthday. I think our invitation got lost in the mail….

TCU had a demo show at the Fort Worth Museum of Science.  Also, love the science tank tops.

TCU had a demo show at the Fort Worth Museum of Science. Also, love the science tank tops.

TCU students performing demonstrations.  Nice use of goggles!

TCU students performing demonstrations. Nice use of goggles!

We Want to See Your National Chemistry Week Pictures!

Hi ACS Student Chapters.  You know what time it is: National Chemistry Week!  And we want to see your pictures!  We know you’ve got neat things planned, like Various Periodic Tables:

Or fun demo shows:

NCW pictureOr…other things (we’re not 100% sure what’s happening in some of these pictures, but it looks like fun!):

 

So email us your NCW pictures, and we’ll post our favorites!  Happy National Chemistry Week, and Happy Mole Day!

Sharing Chemistry with Plays by Fusion Science Theater

Today’s post comes to us from the ACS Student Chapter at Union University in Jackson, TN.  They were awarded a Community Interaction Grant to share their love of chemistry with underrepresented groups in chemistry, and the project you’re about to read about is the result.  Is your chapter interested in doing the same?  Visit the Community Interactions Grant webpage and learn more, and while you’re there, check out our other grants as well!

The Union University student chapter of the American Chemical Society needed a way to encourage student involvement and simultaneously interact with the Jackson, Tennessee, community. Students had a desire to spread their love of science while also working with children, especially those who are underprivileged. A golden opportunity appeared in 2011 in the form of Fusion Science Theater, a program based in Madison, Wisconsin.

Fusion Science Theater creates plays for children based on fundamental science concepts so that they can experience science in an interactive, fun atmosphere. The length of the plays range from 30 minutes to an hour long, and during that time, actors encourage audience questions and participation in demonstrations, and they use ballots to gauge audience attention and comprehension of subjects covered.

Union University students Spencer Rhodes and Brooklin Byrd perform the play "Will It Light?" on March 7, 2013, for elementary students at Alexander Elementary School.

Union University students Spencer Rhodes and Brooklin Byrd perform the play “Will It Light?” on March 7, 2013, for elementary students at Alexander Elementary School.

“What Makes the Loudest Boom?” centers around two actors, one a show host and the other a guest on the show. Children learn about how things burn, how this process relates to gases, and how balloons filled with different gases explode differently when exposed to heat. “That’s the Way the Ball Bounces” is a science show that teaches children how various materials bounce differently based on their molecular bonding.

“What Makes the Loudest Boom?” centers around two actors, one a show host and the other a guest on the show. Children learn about how things burn, how this process relates to gases, and how balloons filled with different gases explode differently when exposed to heat. “That’s the Way the Ball Bounces” is a science show that teaches children how various materials bounce differently based on their molecular bonding.

Union University student Phillip Kurtzweil performs a demonstration for the “What Makes the Loudest Boom?” play on April 12, 2013 at Lane Elementary School.

Union University student Phillip Kurtzweil performs a demonstration for the “What Makes the Loudest Boom?” play on April 12, 2013 at Lane Elementary School.

Phillip Kurtzweil, a junior at Union University, said that having multiple demonstrations keeps the kids engaged. “The kids say, Oh, wow! That’s cool! Flames! But in between the demos, you explain all the topics to them,” said Kurtzweil.

In September 2012, Dr. Randy Johnston, chair of the chemistry department, and two Union students were invited to a three-day training workshop at the Madison Area Technical College to learn a new play called “Will It Light?”, which involved explanations of electricity and how it is conducted through liquids. Through that experience, the Union students learned new techniques to communicate with younger students, enabling student to more concretely understand science concepts. These new skills were tested at the Madison Children’s Museum on the last day of the trip.

For the 2012–2013 academic year, the play “Will It Light?” was added to the lineup, replacing “That’s the Way the Ball Bounces.” Two actors were needed to perform each play, along with stagehands and people to prepare the liquid nitrogen ice cream. These students prepared rigorously for their performances, using fellow Union students and faculty as mock elementary school students to practice demonstrations. Andrew Stricklin, a junior at Union University, said, “I learned that … when people go and put on these plays … it’s a lot of work and it takes a lot of people willing to give up their time.” Demonstrations were scheduled to fit around Union students’ schedules and were performed at various schools in low-income neighborhoods around Jackson.

Union University student Andrew Stricklin encourages audience interaction during the play "What Makes the Loudest Boom?" at Lincoln Elementary School on April 12, 2013.

Union University student Andrew Stricklin encourages audience interaction during the play “What Makes the Loudest Boom?” at Lincoln Elementary School on April 12, 2013.

Upon visiting these schools, Union students were welcomed with open arms by students and teachers alike. Students eagerly bounced up and down to answer questions and yelled out answers when called upon. Tyler Byrd, a junior at Union University, said, “The teachers enjoyed it very much. They thanked us multiple times [for coming] … and they seemed very interested by most of it themselves.”

Students agreed that exposing kids to this game-show form of teaching and interaction encourages children to be inquisitive about the world around them and about science in general. Evan Lewoczko‎, a sophomore at Union University, said, “I think it was really a humbling experience because we realized that was us ever so long ago, and … some of us may have been thinking back to when we first got interested in chemistry.”

Union University students Andrew Stricklin and Phillip Kurtzweil call on students at Lane Elementary School on April 12, 2013.

Union University students Andrew Stricklin and Phillip Kurtzweil call on students at Lane Elementary School on April 12, 2013.

Fusion Science Theater shows allowed Union students to reach out to underprivileged youth in a unique, interactive way, allowing students who may not have had much exposure before to enjoy a hands-on experience in science. In the future, Union faculty and students hope to work together to create a play oriented toward high school students. Johnston, who is also faculty advisor to the Union University student chapter of the American Chemical Society, said that the plays require a lot of group commitment, work, and a clear purpose. Johnston said, “I think other schools should focus on the goal, which is helping students understand science, the scientific principle, and develop an interest in science.”

Brooklin Byrd is from Memphis, TN, and is a senior biology major/chemistry minor at Union University in Jackson, TN. She is involved with many organizations on campus, including the Union University Student Members of the American Chemical Society, in which she currently serves as the chapter secretary. After graduation from Union, Brooklin plans to attend dental school to become a doctor of dental surgery.

Brooklin Byrd is from Memphis, TN, and is a senior biology major/chemistry minor at Union University in Jackson, TN. She is involved with many organizations on campus, including the Union University Student Members of the American Chemical Society, in which she currently serves as the chapter secretary. After graduation from Union, Brooklin plans to attend dental school to become a doctor of dental surgery.

Nerd Heaven: Day One of the Undergraduate Program at the ACS National Meeting in New Orleans

Welcome to nerd heaven! The first day of Undergraduate Programming at the 245th ACS National Meeting in New Orleans is here!

If at any point you need to relax and grab a snack during the day, the Undergraduate Hospitality Center will be in Section BC of Hall A, 8:30 a.m. – 5 p.m.

Want to know more?
Follow us on Twitter
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Check out the Undergraduate Program Guide

This first event is great to get some pointers on how to spend your time here:

Making the Most of Your First ACS National Meeting
Section C/Hall A
9:00 – 9:45 a.m.

Receive some tips on how to get the most out of an ACS national meeting. You will learn where you should go and different things to do from faculty and students who are pros at ACS national meetings.

Don’t you wish there was something like this for graduate school? OH WAIT! Check out this next event!

Graduate School Reality Check Step I: Getting in
Room 209/210
10:00 – 11:00 a.m.

Do you know what type of graduate degree or school is right for you? Learn about some options at this session in addition to what different places look for in their applications. There will be a panel of graduate students, graduate school faculty, graduate school recruiters, and industry representatives to help answer your questions about applying to graduate schools.

If you didn’t get your questions answered, why not go sit down and talk to a graduate school recruiter one on one?

Networking Social with Graduate School Recruiters
Room Hall A Section B
11:00 a.m.– 4:00 p.m.

This networking social is a great chance to learn about many different schools. This is a great time to get questions answered about different graduate programs and some schools you have never heard about. (After this event I kept in contact with a recruiter I met. Through her, I got connected to an admissions counselor who helped me through the application process: And I got in!)

Here are some tips:

Don’t sell yourself; instead, take this opportunity to learn about the school and programs available.

This is a great event to have business cards for and also to collect business cards. NETWORKING!

There are some things every chemist, at grad school or not, should learn. Get a head start by going to a technical symposium and some workshops.

Technical Symposium: Teaching is Fun – How to Become an Exemplary Teaching Assistant
Rivergate Ballroom
1:00 p.m. – 2:30 p.m.

Most graduate programs require at least two semester of a teaching assistantship. This technical symposium will help you learn what to do and what not to do in order to be the best teaching assistant possible.

Being in graduate school also requires research. What good is research if you cannot communicate the results with other scientists? These two workshops are here to help improve your skills on how scientists communicate.

Workshop Essential Skills for Success
Part I: Oral Presentation of Scientific Results
Part II: Write Like a Chemist
Room 206/207
Part I: 2:45 p.m. – 4:00 p.m.
Part II: 4:00 p.m. – 5:15 p.m.

This workshop will provide you with helpful tools for successful oral presentations and paper writing, both important parts of graduate school. This is a great chance to learn something that will later impress those you are working for, because for once they won’t have to teach it to you. This is a great skill to learn even if you are not planning on attending graduate school.

If graduate school isn’t on your radar or your club’s demos need some help, you should check out my favorite event.

Chem Demo Exchange
Hall E2/E3
11:00 a.m.- 12:30 p.m.

This is a wonderful event where you can learn demos from other undergraduate clubs. Bring something to collect all the papers in because you won’t be able to remember how to do all the demos. Many of the demos you even get to try out! More than half of the demos my club conducts we got from this event.

But what if you have great demos and you don’t feel like they reach the people you are doing the demos for?

Making Demos Matter Workshop
Rivergate Ballroom
4:00 p.m.- 5:30 p.m.

This workshop will help transform your demos from things your club members enjoy to play with to events your audiences will learn from and enjoy watching.

And since you have a few minutes before the ceremony, why not enjoy a mini-Mardi Gras at…

Opening Night Parade and New Member Networking Bingo
Expo Hall
6 pm

At 6pm just outside the Expo Hall doors you’ll find a brass band, a float, jesters and revelers, and the ACS Mole. Meet us there as we open the Expo Hall in a festive show of New Orleans flavor, in honor of the newest members of the American Chemical Society — YOU!

Follow the parade to the New Member Networking Bingo event behind the ACS Booth. Join fellow new members, ACS governance members, staff, and a few seasoned members as we play ACS bingo, network, and learn more about what the Society offers you.

Now take a little break and get ready for two of the best events:

Student Chapter Awards Ceremony + Undergraduate Social
Room Hall A/Section C
Ceremony: 7:00 – 8:30 p.m.  Social: 8:30-11 p.m.

You worked hard all year so head to the ceremony to accept your award. There is no reason to miss out on this many nerds cheering.

Every great awards ceremony has an after-party! Continue your celebration at the undergraduate social.

Now it’s time to sleep, so you can attend even more fun events tomorrow! More helpful information about the meeting can be found in the Undergraduate Program Guide. Also, check back tomorrow for Monday’s event highlights!

Countdown to the 245th ACS National Meeting

Hello Undergrads!

The 245th ACS National Meeting will take place this April 7-11 in New Orleans, LA!  And, of course, we have a robust Undergraduate Program to enrich your National Meeting experience!

Click for a larger version.

If you’re going to the meeting, there are a few things you should do in preparation…really soon.

  1. Register your Chapter for the Chem Demo Exchange! Deadline is Friday, March 22! Only a few stations left!  Register now!
    Univ of toledo, Nat'l Meeting Demo Exchange
  2. Sign up for the Undergraduate Speed Networking Event – meet professional chemists who can help them find their place in the world of chemistry: Sign up here!Want to know more about networking?  Read our tips and tricks.
  3. Read our Guide to Undergraduate Programming at the National Meeting
    There will
    be more on this next week, but for know, find out where to find the best undergraduate events, green chemistry symposia, or free food in our National Meeting Guide.

Want to stay up to date on the meeting?  Follow our blog, Like us on Facebook, or follow us on Twitter, and we’ll keep you up to date on all things National Meeting.  See you in New Orleans!

Reaching the Community with Chemistry – A CIG Grant in Action

The ACS Undergraduate Programs Office offers two grants to help your chapter reach the community: the Community Interactions Grant and the Innovative Activities Grant. Both of these grants are due March 21, so if you’re interested, apply now!

Below is an account of what one school, Texas Christian University, did with their Community Interactions Grant, by Erica Zimmerman, TCU Chemistry Club Outreach Officer.

In the spring of 2011, Sandi Dang, President of the Texas Christian University Student Chapter of the American Chemical Society, had a vision for the ACS Dallas – Fort Worth area to work together to foster the love of chemistry among their local community. The result was a week-long set of hands on activities at the Fort Worth History and Science Museum (FWHSM). That event motivated the chapter to expand its program in 2012 by inviting local elementary schools to visit the TCU campus!

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The 2011 participants at the FWHSM Week of Chemistry from University of Texas at Dallas, Southern Methodist University, University of Dallas, Texas Women’s University, Texas Wesleyan University, Dallas Baptist University, University of North Texas and Texas Christian University.

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Happy kids eating ice cream made using freezing point modification techniques! They were always so impressed it just took milk and some sugar to make ice cream!

In order to serve the Dallas/Fort Worth community, the TCU Chemistry Club created a program called “College Scientist for the Day,” which was funded by an ACS Community Interaction Grant. The goal of this program was to introduce kids to higher education in order to show them what they could achieve upon advancing their education. For many of the students, it was their first time on a college campus, and they were often in awe of the sheer size of the university. Many of the kids were excited at the idea of living at school, away from parents, and eating spaghetti every day, if they wanted.

TCU “College Scientist for a Day” starts when students from local elementary schools arrive at the campus and are greeted by TCU faculty and Chemistry Club Members. Activities begin with a “magic show” by faculty and students. The magic show includes eating a candle made of apple, a dissolving snake race, and the crowd-pleasing Super Frog Toothpaste (you may know it as Elephant’s Toothpaste).

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Eating a candle: A corer is used to obtain a cylinder of apple, and a sliver of almond is inserted in the top to act as a wick. Light the almond, and talk about candles and making observations. State that not everything you see is true, and then eat the candle.  Explain that scientists perform experiments in order to gather observations about the world.  We are constantly revising what we know based on what we observe.

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Dissolving snake race: Make a 3-foot snake and a 6-foot snake out of packing peanuts. Fill a 400-mL beaker half way with water, and another with acetone. Give a demo leader (who’s okay with losing) the shorter snake and the beaker of water. Give the 6-foot snake and the beaker of acetone to another. Have the observers guess which snake will be easier to dissolve. They will observe that the acetone dissolves the snake, while the water doesn’t.

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Student leader Erika Zimmermann showing that sodium polyacrylate absorbs water and thus none will fall out over Lauren’s head, or so she hopes!

After the magic show, students are divided into groups of about 20 and are escorted up to actual TCU teaching labs. In the labs, students don protective eye wear, and TCU Chemistry Ambassadors guide the students through the ACS Jiggle Gel Kits. The group leaders are TCU undergraduate and graduate students from both the chemistry and biology departments. Two TCU student leaders lead each student group through making polymers.

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Students showing off the slime they made!

After the lab session, the remaining time is spent on a question-and-answer session with TCU students about college. Students talk about what it’s like to be in college, what classes they take, what professors are like, where they live, what they do with their free time, and so much more. Then the chapter takes the students on a mini tour of campus, visiting the Monning Meteorite Museum, the library, administrative buildings, and dorms. The kids leave tired and happy – and hopefully knowing a little more about the world of a college student.

Thanks for sharing, TCU!  And remember, apply for a Community Interactions Grant or an Innovative Activities Grant today! Questions? E-mail undergrad@acs.org or leave a comment.

Spectroscopy at Home

Kirchhoff and Bunsen were first dazzled by the interaction of matter and light 152 years ago. While a long list of scientists and discoveries contributed to their level of investigation, Kirchhoff and Bunsen were likely the first true spectroscopists.

One of the principal things that interest me is the interplay between light and matter. It’s the basis for radio communication, harnessing energy from our sun, and an incredibly accurate quantitative measurement. As a child growing up, I had an insatiable hunger for knowledge on the subject, which is not quite available to a child. My father would offer up his explanations and I would try to extract information from the Internet, but nothing was digestible to me.

This illustrates an important motivation for designing this demo (below). In my search for answers on the nature of light and its interactions with matter, I was exposed to ideas on relativity, quantum mechanics, chemistry, and physics.   These were necessary to understanding light, at least understanding it as much as possible. Later, when I had to study these topics in school I was excited to put in the work.

By the time I reached college and started studying chemistry, I was surprised how quickly the fine details of spectroscopy were skipped over. Students are taught to take for granted the subtle interplay between photons and atoms. I hope the demonstrations listed below will help your chapter demonstrate these fantastic principles. This is not meant to be an end-all guide, but an inspirational and fun note on self-discovery.

Experimental

There are two simple experimental set-ups useful in illustrating the basic principles of spectroscopy. The first simply involves passing light through homemade samples and noting which phenomenon is occurring: absorption, scattering, or emission. The second experiment focuses on how chemists design an instrument in general, and then uses that equipment to support inquiries about the physical world.

Light and Matter Demo

Materials:

  • A set of red, green, and UV/blue laser pointers
  • Glass sample containers
  • Solvent (water or ethanol)
  • Samples (highlighter, food coloring, and milk)

Procedure:

  1. Begin by filling your sample containers with solvent. Most household samples will be water-soluble.
  2. Dissolve a different sample into each sample container. This can be done by rubbing the highlighters tip vigorously against the bottom of the container until the solution changes color. You can also make sample solutions by adding food coloring to your solvent. A very dilute solution of whole milk will also serve as a light scattering example. As always be sure to save one container of solvent as a blank (no sample).
  3. Try to develop a hypothesis before analyzing your samples. You should be able to predict which sample will absorb your chosen laser.
  4. Test out your various laser pointers by passing them first through the blank and then into your sample container.

    From: laserpointerforums.com/f51/make-your-own-flourescent-dye-37532.html

What is going on here?

The first thing is to note the use of a laser. Lasers emit a coherent beam of monochromatic light (a narrow distribution of wavelengths). When you pass your red laser through a solution of green dye we see total absorbance; in general, green materials absorb red wavelengths of light and reflect or scatter green wavelengths back towards our eyes. Secondly, these demos can be expanded to illustrate emission from a sample. By using your blue/UV laser in conjunction with a solution of highlighter dye, you will see a brilliant luminescence from the solution. The fluorophores within highlighter dye absorb and emit much more intensely when stimulated directly with UV light. To take this demonstration further, coat a piece of cardboard with glow in the dark paint. Several seconds after excitation with your blue/UV laser you will continue to see light emitted from the paint. This is a special case of emission called phosphorescence. The concepts behind phosphorescence are closely related to fluorescence but certain processes take a longer time, leading to a delay before relaxation of the system. Scattering can be observed with dilute solutions of milk. The protein polymers present in milk assume a globule-like conformation of the appropriate diameter to scatter visible light. You should observe dispersion of your beam throughout the sample as a result.

Oh, and if you want to impress someone at a party, you can fluoresce a gin and tonic.


The Shoe-Box Spectrometer Demo

Materials:

  • A white-light source
  • A 3×5 inch note card
  • A shoebox
  • Flat-black spray paint
  • Black duct tape
  • Black card stock
  • Scissors
  • Hot glue
  • A diffraction grating (A pair of children’s fun color glasses, the type you put on and look around at lights to see amazing radial distributions of rainbow, make suitable diffraction gratings)
  • A prism

Procedure:

  1. Begin by painting the inside of your shoe box with flat-black spray paint. This coating prevents stray light from reflecting within the instrument.
  2. Construct a cube from card stock that is slightly shorter than the height of your shoe box. The width should be about 2-3 inches. The top of the cube should be free to open and close, and no bottom is required.
  3. On opposite sides of your card stock cube cut a very thin slit (about 2 mm) and a larger slit (about 5 mm).
  4. Using duct tape, attach the diffraction grating centered over the thin slit.
  5.  Butt the card stock cube against the rear (long end) of the shoe box top. Be sure to leave room for the bottom to fit between the cube and the lid lip. Finally secure the cube to the lid with duct tape and glue.
  6. Place the shoe box lid down and lay the box on top. Make note of where the large slit of the sample chamber lays in conjunction with the shoe box. Cut a slit or hole that is about 10 mm in the shoe box directly behind the large slit. The decreasing slit widths will help to collimate your light source.
  7. Align your light source behind the entrance slit and turn it on. Light should pass into the sample holder through the large slit, and out through the thin slit/ diffraction grating. Turn off the lights and use your note card to get a feel for where the best image is produced after the light exits the diffraction grating. It may be necessary to place a prism between the light exiting the diffraction grating and your note card in order to help spread the spectral lines.
  8. Once you have found a suitable arrangement, tack down the prism and note card with hot glue. The final step is to cut a suitable viewing hole in your shoe box. This should be positioned so that you can clearly see the note card but minimal stray light can enter.
    shoe box spectroscope

Operation

You should be able to use sample from the Light and Matter experiment above to test your instrument. First take note of the spectrum produced by your light source alone. It may be useful to place a number line on your note card to mark where certain spectral lines appear. Next, take a sample and place it with in your card stock sample chamber and observe the new spectrum produced. If your sample absorbs in the region of the electromagnetic spectrum produced by your light source you should see certain spectral lines removed from the spectrum produced on your note card.

What is going on here?

Using a polychromatic light source such as an incandescent light bulb produces all the colors of visible light that we are familiar with. As light passes through your diffraction grating it is dispersed into its components, which we can observe as the ROYGBIV rainbow on our note card. When we place a sample in the instrument we expect interaction between the sample and the incident light. For instance, if we place our solution of green dye (it should be noted that a fairly dilute sample is required) in the instrument, then we should see absorption of the red wavelengths present in our light source. As light exits the sample and is dispersed by the diffraction grating, we will no longer see lines in the red portion of our rainbow.

In general, what we have done is take the principles learned during the Light and Matter demonstration and build an instrument that exploits those mentioned phenomena to tell us something about the physical world. Everyday scientists use spectrometers of this type to identify unknown compounds in mixtures.  In general, analytical instruments have a simple scheme, a stimulus, a sample holder, and a detector. While today’s computer driven instruments may seem intimidating, for the most part, they follow the above scheme. Our eyes make excellent detectors, so try to think of what other household instruments you can construct.

Conclusion

Teachers can use this simple setup with containers of house hold chemicals to show how they subtract from the spectrum of your incident light source.

If you play around with light sources, you quickly realize LED light sources don’t produce a full spectrum. You can ask students to recognize that light emission in LEDs must be due to a different mechanism than that in an incandescent light bulb. The slit has major effects on performance.  Students are encouraged to start by trying to cut into a note card; they will see that the slit transmits a minuscule amount of light. Encourage them to try and make wider slits. Next, you might saw a slit in a small piece of wood. Finally, note that razor blades make immaculate slits (note, use proper safety when using the razor!).

It is amazing how much you can learn from empiricism. Trial and error teaches a student why cuvettes are square, why slits are made of metal, why the spectrometer is closed into a box, and why that box is black on the inside. Further, students start to appreciate how mathematics can be used to tune the distances between elements and focus your spectrum.

Exploration of science through hands-on experience reenforces learned theory and is lots of fun, too.

More on the Theory of Spectroscopy

Spectroscopy comes in many varieties, categorized by the type of light involved. In a spectroscopy experiment we primarily measure light before and after it interacts with a sample; this often leads to the name “spectrophotometry”. However, we can also make spectrophotometric measurements just by observing a sample that has been stimulated by another form of energy. In fact, the earliest spectrophotometric measurements by Kirchhoff and Bunsen were of this type; a metal was dissolved in solution or powdered and placed into a flame, where new colors were emitted in the flame and analyzed.

The underlying principle of spectroscopy is light’s ability to interact with matter. Light demonstrates wave-like properties with electric and magnetic fields that oscillate perpendicular to each other. Because matter is composed of atoms, which possess charged particles, there is an electric field present for light to influence. We observe this everyday through visible properties such as color, opaqueness, transparency, luster, and more. Each of these observed properties arises from a fundamental interaction of light and matter, including absorption, scattering, and emission.

Absorption: When an atom or molecule is struck by an incident photon, the energy of that photon is stored in the atom or molecule briefly. The energy of the incident photon, which is wavelength-dependent, determines the mechanism of storage.

Scattering: When light waves propagating through a medium interact with irregularities whose size is on the order of the propagating light waves’ wavelength, scattering occurs. Scattering can be divided into two categories: elastic and inelastic. In elastic scattering, an incident beam of light is caused to divert from its original path. An example of this is our blue sky; as white light from the sun hits our nitrogen-rich atmosphere, the nitrogen is effective at scattering the blue components of visible light. Because the blue light no longer follows a direct path through the atmosphere, we observe blue light throughout the sky. Further, as you look towards the horizon, you are looking through more atmosphere; blue light is scattered to an almost imperceptible amount, so at sunset we primarily see red light, which transverses the atmosphere largely unaffected.

In the inelastic case of scattering, the energy of the incident photon and the scattered photon differs. The change in energy can give the observer information on the motion or activity of the scattering centers.

The mechanisms that lead to scattering are out of the scope of this article but are worth looking into. It is important to note that absorption and emission are involved in producing a scattered beam of light. Scattering is more a resulting property of the bulk phase of a material than the result of a single photon interacting with a single atom or molecule.

Emission: When we have excited an atom or molecule to a higher energy state, it will at some point later relax back to its ground state (state of lowest energy). When the system relaxes, a photon of lower energy than the stimulus is produced.

Malcolm Davidson is a senior chemistry student at Louisiana State University. You can reach him at mdavi15@tigers.lsu.edu for comments, suggestions, or just to talk shop. Photos courtesy of Jacob D. Mcalpin.

References and Further Reading:

Kirchhoff, Gustav, and Robert Bunsen. “Chemical Analysis by Observation of Spectra.”Annalen Der Physik Und Der Chemie 110 (1860): 161-89. Print.

Thomsen, Volker. “A Timeline of Atomic Spectroscopy.” Spectroscopy 21.10 (2006): n. pag. Spectroscopy Online.

Alexander Scheeline and Kathleen Kelley. “Cell Phone Spectrophotometer.” Cell Phone Spectrometer. N.p., n.d. 21 Nov. 2012. http://www.asdlib.org

Increasing the Visibility of Women Scientists: 3 Modest Proposals

While roaming the streets of Berlin, Germany over the course of the last week, I surveyed 50 people representing all ages, colors, races, and sexual orientations and asked them which 5 scientists first came to mind. Seventeen could not think of any scientist’s name, 15 responded incompletely with less than 5 scientists, and only 18 could complete the task at hand. It was no surprise that Albert Einstein would rank number one, but it was not expected that the sum of all women scientists named on the streets of Berlin would tie with the (un)popularity of one, Svante Arrhenius. Out of the 41 scientists mentioned, only two women’s names came up: Elizabeth Blackwell and Marie Curie. It was discouraging, to say the least, to witness the entirety of women’s contributions to science acknowledged by only 4% of participants in such a cosmopolitan city.

scientsits graph

Note: Numbers are rounded up, so total exceeds 100

The results of this study reveal that a general knowledge of science, scientists, and their contributions is severely lacking. It’s quite unbelievable that 34% of the approached individuals were not able to mention even one scientist. The other, perhaps more stunning, statistic is surely that less than 5% of the entire sample population mentioned a female scientist. Given the challenges facing the environment, our current economy, and the ever-developing world of technology, the world needs every potential scientist it can get, but gender has often become a barrier (see resources at the end of this post). Although we as a people have become nearly inseparable from our electronic devices, namely, the computers on which you’re reading this post, we do not recognize the women who contributed to today’s technology, such as the first computer programmer, Augusta Ada King (aka Ada Lovelace); Ruchi Sanghvi, the first female engineer at the world’s most – known social networking site, Facebook; and Google’s first female engineer, Marissa Mayer, who is now the CEO and president of Yahoo!

How is it that modern – day media supports and advertises the accomplishments of prominent male scientists, but women are nowhere to be found? Not surprisingly, every individual I spoke to who could name a scientist knew of Albert Einstein, what he looked like, and his scientific contributions. Although female contributions to the scientific community have indeed been tremendous, women have failed to reach the height of scientific celebrity. Educating the world’s population about the contributions of female scientists may appear to be unachievable for us as individuals, but there are a few simple yet effective ideas with which we can start correcting this problem. In order to begin solving the problem of women’s invisibility in science, I propose three suggestions, ranging from local to national, which we can all put into practice.

First, let’s take advantage of what our student chapters do best: chemistry demonstrations.  No one does chemistry demos like ACS student chapters, and we should play to that strength. So here’s my proposal: Add one demonstration to your repertoire that you can use to highlight the work of a woman scientist. Need an idea? Below you will find a link to a demonstration based on the work of Maud Menten.

Next, we need to make information on women scientists readily available. While you could undertake awareness campaigns, a tool already exists that everyone uses to discover more about the world: Wikipedia. This is why the Royal Society recently sponsored a Wikipedia Edit-a-thon to bring many notable science heroines to light. This is an easy activity that a chapter can do with the help of a few volunteers and some time in the library.

Finally, and most ambitiously, we should push for the creation of a National Woman Scientist Month, in the model of African American History Month, perhaps as a supplement to Ada Lovelace Day.  As Black History Month has demonstrated, a designated period of time to honor and learn about individuals who would otherwise be neglected in significant discussions has not only improved awareness, but also tolerance. We could publicize this event through television channels, newspapers, and websites, as well as encourage our schools, after-school programs, colleges, and universities to participate in this movement and help educate our society about a world of science that includes women. We also need to contact our local politicians to encourage them to support this initiative.

As I saw on the streets of Berlin, the public is critically unaware of the contributions of women in science, but thankfully it doesn’t have to be that way. As ACS student members, we are in a great place to undo the mistakes of our past, on a grand scale or a simple one.

Some articles and resources: