### 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. They will then 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, and 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, using 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 Handout (attached, one per student)

Lesson Handout with Teacher's Notes (attached)

Data Table handout (attached, one per student)

Sample Data handout (attached, optional; for your reference or to show examples to students)

Tweet Up handout (attached, optional; one half-sheet per student)

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 pencils or markers

### Engage

Before you begin, pass out a copy of the attached **Lesson Handout** to each student. Use the attached **Lesson Slides** and **Lesson Handout with Teacher's Notes** as you guide students through the lesson. Briefly review **slides 1–3, **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.

Direct students to the Engage section of the Lesson Handout. The next two slides provide an overview of the questions posed in this section. Move to **slide 4,** and let students consider questions 1 and 2 on their own or with Elbow Partners. Depending on your preference, ask them to record their answers either in their lab notebook or on the handout.

Display **slide 5.** 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. You might utilize the attached **Sample Data** sheet. Explain your plan for the lab workflow (see setup options below) and discuss safety concerns.

### Explore

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. 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 6** to show what spectra should look like as students work on their technique. (See additional tips below.) It can be surprisingly tricky to see the spectra produced by a spectroscope, and seeing the example will help many students.

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.

After the activity, return the ambient light to the room. Direct students to step 3 on their handouts, asking them to form peer groups to compare results and ensure that everyone has data.

Use **slide 7** 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

At the end of the first class period, at the start of the next class, or as homework, have students answer the Explain questions from the Lesson Handout. You can ask students to work individually or in small groups. Encourage them to take chances and make hypotheses using their own words.

Follow up with a whole-class discussion about the questions. Questions 1–4 are close to the data and should be relatively easy for students to address. Questions 5-10 will require additional discussion. Use **slides 9 and 10** to assist with this discussion.

### Extend

Direct students to the Extend section of their 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 12**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 13**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 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 14**to introduce these questions.**Slide 15**shows work for an answer to question 5.

### Evaluate

Direct students to the Evaluate section of their handout. Depending on your goals for the lesson, you can choose to have students complete one, two, or all three of the evaluation activities, which are described below. All three options are suitable for students at various math and science levels.

Tweet Up Exit Ticket. The Exit Ticket described in the Explore section and on slide 8 can be used as an end-of-lesson assessment. You can have students share their tweets online or use the attached

**Tweet Up**handout to write their responses.Extend question discussion. Use the Three Stray, One Stays strategy described on

**slide 16**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 17,**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

Atmospheric Optics. (n.d.). Glowing gases - aurorae. https://www.atoptics.co.uk/highsky/auror3.htm

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.). Tweet up. Strategies. https://learn.k20center.ou.edu/strategy/130

K20 Center. (n.d.). Three stray, one stays. Strategies. https://learn.k20center.ou.edu/strategy/85

Northern Lights Centre (n.d.) Northern lights. https://www.northernlightscentre.ca/northernlights.html

NPR's Skunk Bear. (2017, July 3). The science of firework color [Video]. YouTube. https://youtu.be/dW5OBrB4MRM