Spectrum and Chemical Composition Objectives • The students will understand how scientists use the electromagnetic spectrum to learn about the universe. • Students will understand the importance of using electronic devices to detect invisible forms of light. Suggested Grade Level 6-8 Subject Areas Science Language Arts Art Timeline 1-2 class periods Background Students should have prior knowledge on how to access the Internet web pages and basic knowledge of computer keyboarding. Students should have prior knowledge of the electromagnetic spectrum and how important it is to learn about the universe. The light that we see with our eyes-or visible light- represents only a small portion of the electromagnetic spectrum. Developing the technology to detect and use other portions of the electromagnetic spectrum-the “invisible” light that our eyes cannot see- has had a tremendous impact on our daily lives. Then you listen to the radio, heat your food in a microwave oven, use a remote control, or have an X-ray taken, you are using “invisible” light. In astronomy, scientists use the properties of light to learn about celestial objects that are too far away to visit. Each portion of the electromagnetic spectrum provides unique clues about the nature of the universe. The missions and research programs in NASA’s Astronomical Search for Origins program uses innovative technologies to observe the universe at a variety of wavelengths (ultraviolet, visible, and infrared) in search of the answers to two enduring questions: Where did we come from? Are we alone? Vocabulary • Electromagnetic Energy: A from of energy that travels through space as vibrations of electric and magnetic fields; also called radiation of light.

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Frequency: Describes the number of wave crests passing by a fixed point in a given time period (usually one second). Frequency is measured in Hertz (Hz). • Spiral Galaxy: A large pinwheel-shaped systems of stars, dust, and gas clouds. • Wave: A vibration in a medium that transfers energy from one place to another. Sound waves are vibrations passing in air. Light waves are vibrations in electromagnetic fields. • Wavelength: The distance between two wave crests, which it the same distance between two troughs. To help identify and understand the makeup of celestial objects, scientists use devices called spectrographs to disperse, or separate, the light from celestial objects into its components wavelengths. Features in the resulting spectrum help astronomers to measure an object’s properties, such as its temperature, composition, density, and motion. Scientists in NASA’s Astronomical Search for Origins program will image stars and galaxies at ultraviolet, visible, and infrared wavelengths. They will also look for characteristic patterns of light or spectral “fingerprints” emitted by atom and molecules to measure elements in the early universe and to search for signatures of life. Combining the light from multiple telescopes will allow us to achieve the capabilities needed to identify and study terrestrial planets orbiting nearby stars. Pre-lab Discussion/Background Some elements-such as sodium, calcium, strontium, and potassium are classified as metals because they conduct heat and electricity and have certain other properties in common. Metals often combine with nonmetals to form compounds. For example, the metal sodium will combine with the nonmetal chlorine to form the compound sodium chloride, which is common table salt. When compounds of certain metals are heated, the metals give off wavelengths of visible light. Each metal gives off wavelengths that are different from the wavelengths produced by other elements. The light is divided when you use a spectroscope-an instrument that breaks light into its component colors. By using a spectroscope to examine the light from a flame, you can tell weather certain metals are present in the flame. Scientist can learn about stars and other bodies in space by studying the spectrum of the electromagnetic wave each of these objects give off. In this investigation, you will observe the colors produced by compounds of certain metals when they are heated. You will use a spectroscope to examine the spectrums of several different metals. Materials Paper towel tube Diffraction grating Black tape (electrical) Scissors Art supplies

White paper Colored pencil Paper Towel Chemical Supplies Bunsen burner Igniter Hand-held spectroscope (student constructed) Nichrome wire loops with handles, (one per solution, dipped in solutions of calcium chloride, potassium chloride, and sodium chloride) Lesson 1. The students will assemble a spectroscope. 2. Procedure: (30 minutes) At one end of the paper towel tube se the black tape to cover the end of the tube, leaving a slit about 3mm in width down the center of the tube. At the opposite end of the tube cover the opening with a piece of grating material cut from a sheet. It is important that the scratches on the grating material are parallel to the slit in the other end of the tube. Tape the grating lightly in place until you are sure the grating is parallel to the slit, (teacher assistance), and then secure it. The final device is a simple spectroscope, a device used for forming and examining the unique combination of colors that make up any light. These colors are called a spectrum (plural: specra). 3. Using the spectroscope to view the spectrum of different chemical compositions and making chart of each using colored pencils and paper. 4. Procedure: (45 minute) NOTE Read through entire procedure before you begin! Remember to follow all Safety Guidelines while carrying out this investigation. A) Light the burner and adjust it to give off a hot blue flame. B) Look at the flame through the spectroscope. The slit of the spectroscope should be vertical. Rotate the eyepiece to make a sharp spectrum on the sidewall of the spectroscope. Each group member should observe this spectrum. C) While you are looking at the flame through the spectroscope, have a classmate carefully hold in the top of the burner flame a nichrome wire loop that has been dipped in a calcium chloride solution. Be sure to look at the flame from the wire loop not form the burner. In Observations, draw what you see through the spectroscope as the sample burns. Use colored pencils. Each group member should observe the calcium spectrum. D) Repeat step 3. with the wire loops dipped in solutions of strontium chloride, potassium chloride, and sodium chloride. To avoid contamination be sure to use a different nichrome wire loop for each solution. In Observations, draw the spectrum for each metal.

Extensions Unknown solution, have students plan how they will find out what metals is in an unknown solution. Will you use a spectroscope? What factors must remain constant? Write down your procedure on a separate sheet of paper. Evaluation The evaluation of the students will be based on their construction of their spectroscopes and on their observation drawings. Also, I will use a work sheet, that has the students analyze and conclude and apply critical thinking skills. Resources Space Discovery A Graduate Course for K-12 Educators, Space Technologies for the classroom. Space Foundation-UCCS More information on the electromagnetic spectrum is available at: The Far Ultraviolet Spectroscopic Explorer: www.fuse.pha.jhu.edu The Hubble Space Telescope: www.amazing-space.stsci.edu The James Webb Space Telescope: www.nextgen.stsci.edu The Space Infrared Telescope Facility: www.sirtf.caltech.edu The Stratospheric Observatory for Infrared Astronomy: www.sofia.arc.nasa.gov Addendums: (1)

Addendum 1

Spectrum and Chemical Composition Worksheet ANALYZE AND CONCLUDE

1. Why must you use a different nichrome wire loop for each substance?

2. How did the spectrums of the samples differ?

3. If all the bancs you observed were drawn on one band, what would it look like?

CRTICAL THINKING AND APPLICATIONS

1. How do the samples resemble stars? How can scientists tell what elements are in a distant star?

2. Spectral lines are often called fingerprints of the elements. WHY?

3. When you are heating the nichrome wire loops, what is the responding variable? What is the manipulated variable?