Summary
In this lesson, students will observe the colors in emission spectra for different excited gases. They will compare the specific emitted wavelengths and explain how these specific emitted wavelengths are the result of energetic and physical transitions by electrons in excited atoms. Then, they will apply this experience with emission spectra to predict and compare the spectra of atmospheres for planets in our solar system.
Essential Question(s)
How do excited gas atoms emit specific colors of light? How can these specific colors be used to explore the composition of planetary atmospheres?
Snapshot
Engage
Students hypothesize about the origin of "neon" colors, what types of gases would allow a planetary atmosphere to support life, and how we measure the composition of planetary atmospheres.
Explore
Students view glass tubes filled with various gases before and while they are excited by electricity and use spectroscopes to observe and record spectra.
Explain
Students work with simple Bohr models to formulate a physical and energetic explanation for the emission of specific colors of light. Students explore the relationship between light wavelength and energy by correlating specific light colors emitted with specific energy changes. Optional video and kinesthetic activities help students explain their observations.
Extend
Extension options for students include predicting the emission spectra of gases from different planets in the solar system, exploring and explaining the Northern Lights phenomenon, and performing Algebra 1-level energy calculations.
Evaluate
Evaluation options for students include writing a data table title that effectively summarizes the key lesson of the exploration, sharing the results of their extension research, or designing their own multi-colored electrified gas sign.
Materials
Lesson Slides (attached)
Lesson Guide (attached; one per student)
Lesson Guide with Teacher's Notes (attached)
Data Table handout (attached; one per student)
Sample Data handout (attached; optional)
Spectrum tubes (The Vernier set includes He, H2, Ne, Ar, N2, CO2, and Air. If you have access to a different set of tubes, use those.)
Spectrum tube carousel (Vernier Carousel is available to check out upon request, but any electrification device that matches your available tubes will work.)
Spectroscopes (Triangular spectroscopes sold by Flinn or tube spectroscopes sold by EISCO are good options, though other brands and homemade work as well.)
Colored pens, pencils, or markers (one set per group of students)
Poster paper (optional; one per group)
Preparation
You can choose to use the Lesson Guide handout or have students use their science or lab notebooks for this lesson.
Lab Setup Options
Before the Explore activity, assess your material supply and decide whether you will have students view the gas tubes as part of a whole-class demonstration or as a station activity. If you have access to only one spectrum tube carousel or excitation box, consider performing a demonstration or using this activity as one station in a lab with other rotations. For example, you could include this activity in a rotation that also includes a chemical flame test experience. If you have access to more than one carousel or excitation device, consider placing different gas tubes at different stations and having students rotate to view them independently. This approach has the advantage of making sure students who work at different speeds have sufficient time to record the spectra.
Engage
20 Minute(s)
Use the attached Lesson Slides and Lesson Guide with Teacher's Notes as you guide students through the lesson. Briefly review slides 2–4, introducing the lesson title, essential question, and lesson objectives. The main goals of this lesson are for students to observe line emission spectra, explain how these spectra result from physical and energetic changes in atoms (electron transitions), and apply line spectra to astronomy as a tool for analyzing the composition of planetary atmospheres. Spectroscopy is a broadly used tool with applications throughout physics, chemistry, and biology. Depending on the course you're teaching, weigh the electronic structure and astronomy goals to fit your needs.
Pass out a Lesson Guide to each student and direct them to the Engage section of the handout. Move to slide 5, and let students consider questions 1 and 2 on their own or with Elbow Partners. Ask them to record their answers on the handout.
Display slide 6. Introduce the spectrum tube carousel and gas tubes that you'll be using in the next activity. Demonstrate the use of a spectroscope and show students an example of a spectrum. Explain your plan for the lab workflow and discuss safety concerns. Have students record the answers from this discussion on their Lesson Guide handout.
Explore
30 Minute(s)
Distribute the attached Data Table and spectroscopes to the students. Depending on your spectroscope supply, form groups as necessary. Ideally, you'll have one spectroscope for every 1–2 students, but the lesson can be done with a more limited supply and larger groups. The larger the group, the more you will need to manage turn-taking.
Have students turn to the Explore section of their handouts and minimize ambient and overhead lights. Display slide 7 and let students get their bearings with the spectroscopes by following step 1 to view natural light and/or overhead lighting. Remind students not to look directly at the sun. The broad rainbow spectra are easier to see than the line spectra emitted by specific gases.
Use slide 8 to show what spectra should look like as students work on their technique. It can be surprisingly tricky to see the spectra produced by a spectroscope, and seeing the example will help many students.
Display slide 9 and ask students to view the gas tubes with and without the spectroscopes, following step 2 in their handouts. If you are working with one carousel or excitation device, you will set the pace for viewing the tubes. Make sure to first show the tubes without electricity (under which conditions they will all appear colorless) to emphasize electricity's role in color production. Provide students with colored pens, pencils, or markers to create their data table.After the activity, return the ambient light to the room. Display slide 10 and direct students to step 3 on their handouts, asking them to form peer groups to compare results and ensure that everyone has data.
Display slide 11 to introduce principles of scientific titles, and then ask students to add a title to their data table. Have students share their titles with you and other classmates as a mid-lesson formative evaluation or an Exit Ticket for the first class session. Typically, it takes about one class period to introduce the lab and gather data.
Explain
30 Minute(s)
Display slide 12 and have students answer the Explain questions from the Lesson Guide. You can ask students to work individually or in small groups. Encourage them to take chances and make hypotheses using their own words.
Once students have completed answering the questions, discuss as a whole-class. Use slides 13-14 to assist with this discussion. Questions 1–4 are close to the data and should be relatively easy for students to address. Questions 5–10 will require additional discussion.
Extend
10 Minute(s)
Direct students to the “Extend” section of their Lesson Guide handout. Assign specific questions from this section that best support your goals for the lesson. Students can complete the questions individually or in groups, in class, or as homework.
Core extension questions 1 and 2 give students a chance to see an astronomy application of the spectra observed in the Explore activity. Use slide 16 to orient students to these questions.
Optional extension question 3 allows students to connect a natural phenomenon (the Northern Lights) to the gas emission observations and explanations. It is best suited for classes with the available time and interests in earth and space sciences. Use slide 17 to introduce this question.
Optional extension question 4 gives students a chance to discuss qualitative and quantitative methods of measurement and scientific communication. This discussion is accessible to students at all math and science levels.
Optional extension questions 5 and 6 offer an opportunity for quantitative practice. The equation is a two-variable inverse equation (y=constant/x) that can be used in Algebra 1 and physical science classes. The equation is not introduced at depth in this handout, so it will be more accessible to students who have been previously introduced (at least qualitatively) to the relationship of energy and light frequency. Use slide 18 to introduce these questions. Slide 19 shows work for an answer to question 5.
Evaluate
15 Minute(s)
Direct students to the Evaluate section of their Lesson Guide handout. Depending on your goals for the lesson, you can choose to have students complete one or both of the evaluation activities, which are described below. Both options are suitable for students at various math and science levels.
Extend question discussion. Use the Three Stray, One Stays strategy described on slide 20 to have students share the results of their Extend question research in peer groups. Split the class into groups of four and assign each group one Extend question. Give each group time to discuss and take brief notes over their assigned question, coming to a consensus. Ask one student per group to stay, acting as a group representative to describe the group's answer and reasoning to other students as they move through the room. Ask each of the remaining group members to stray, each traveling to a different question group (that is, not all going to the same table). Ask students to interview the representative in their new group to gain a deeper understanding of the answer to the question. Students should take notes and then return to their original groups to share what they have learned. Ask each group to synthesize the information they learned and share it with the class.
Design a sign for the school. Invite students to get creative and design a sign that uses electrified gas tubes to produce the desired colors. Using the directions on slide 21, students should perform research to find gases that can make other colors that they haven't seen in the lesson, and then draw a diagram to show the design for their sign, making sure to label the gas used for each portion.
Resources
K20 Center. (n.d.). Bell ringers and exit tickets. Strategies. https://learn.k20center.ou.edu/strategy/125
K20 Center. (n.d.). Elbow partners. Strategies. https://learn.k20center.ou.edu/strategy/116
K20 Center. (n.d.). Three stray, one stays. Strategies. https://learn.k20center.ou.edu/strategy/85
NPR's Skunk Bear. (2017, July 3). The science of firework color [Video]. YouTube. https://www.youtube.com/watch?v=dW5OBrB4MRM