Emission Spectra - Juniata College发射光谱-朱尼亚塔学院.doc

Juniata College Science in MotionEmission Spectra“The Elements”Juniata College Science in MotionVocabularyAtomElementSpectrum (any of the following types of spectrum listed below)Electromagnetic spectrum (EM)ElementMoleculeWavelengthVocabularyAll definitions are from Atom A unit of matter, the smallest unit of an element, having all the characteristics of that element and consisting of a dense, central, positively charged nucleus surrounded by a system of electrons. The entire structure has an approximate diameter of 10-8 centimeter and characteristically remains undivided in chemical reactions except for limited removal, transfer, or exchange of certain electrons. This unit regarded as a source of nuclear energy. Element A substance that cannot be reduced to simpler substances by normal chemical means and that is composed of atoms having an identical number of protons in each nucleus. Any of more than 100 fundamental substances that consist of atoms of only one kind and that singly or in combination constitute all matter Each element emits a unique spectrum. These elements can be identified by their wavelengths in nanometers. /hbase/vision/specol.html#c1Emit to give off or send out (the process is called emission)Energy :the ability to do work; light is a form of energyLight Electromagnetic radiation that has a wavelength in the range from about 4,000 (violet) to about 7,700 (red) angstroms and may be perceived by the normal unaided human eye. Common term for electromagnetic radiation of any wavelengthThe Spectrum of Visible LightThe visible part of the spectrum may be further subdivided according to color, with red at the long wavelength end and violet at the short wavelength end, as illustrated (schematically) in the following figure. The visible spectrum /astr162/lect/light/spectrum.html/main/news/stories/science_teacher.php?news_story_ID=48612&print=yesMolecule:The smallest particle of a substance that retains the chemical and physical properties of the substance and is composed of two or more atoms; a group of like or different atoms held together by chemical forces. A molecule will emit a spectrum from the combination of elements that it possesses. (Physics) The smallest part of any substance which possesses the characteristic properties and qualities of that substance, and which can exist alone in a free state. (Chem.) A group of atoms so united and combined by chemical affinity that they form a complete, integrated whole, being the smallest portion of any particular compound that can exist in a free state; as, a molecule of water consists of two atoms of hydrogen and one of oxygen. Cf. Atom.SpectrumThe distribution of a characteristic of a physical system or phenomenon, especially: The distribution of energy emitted by a radiant source, as by an incandescent body, arranged in order of wavelengths. The distribution of atomic or subatomic particles in a system, as in a magnetically resolved molecular beam, arranged in order of masses. The distribution of a characteristic of a physical system or phenomenon, especially the distribution of energy emitted by a radiant source arranged in order of wavelengths. The color image presented when white light is resolved into its constituent colors: red, orange, yellow, green, blue, indigo, violet. The plot of intensity as opposed to wavelength of light emitted or absorbed by a substance, usually characteristic of the substance and used in qualitative and quantitative analysis. The distribution of atomic or subatomic particles in a system, as in a magnetically resolved molecular beam, arranged in order of masses. a continuum of color formed when a beam of white light is dispersed (as by passage through a prism) so that its component wavelengths are arranged in order any of various continua that resemble a spectrum in consisting of an ordered arrangement by a particular characteristic (as frequency or energyELECTROMAGNETIC SPECTRUM (2) : MASS SPECTRUM c : the representation (as a plot) of a spectrum. (a)The several colored and other rays of which light is composed, separated by the refraction of a prism or other means, and observed or studied either as spread out on a screen, by direct vision, by photography, or otherwise. (b) A luminous appearance, or an image seen after the eye has been exposed to an intense light or a strongly illuminated object. When the object is colored, the image appears of the complementary color, as a green image seen after viewing a red wafer lying on white paper. Called also ocular spectrum. Absorption spectrum, the spectrum of light which has passed through a medium capable of absorbing a portion of the rays. It is characterized by dark spaces, bands, or lines. The electromagnetic spectrum, broken by a specific pattern of dark lines or bands, observed when radiation traverses a particular absorbing medium. The absorption pattern is unique and can be used to identify the material. Chemical spectrum, a spectrum of rays considered solely with reference to their chemical effects, as in photography. These, in the usual photogrophic methods, have their maximum influence at and beyond the violet rays, but are not limited to this region. Chromatic spectrum, the visible colored rays of the solar spectrum, exhibiting the seven principal colors in their order, and covering the central and larger portion of the space of the whole spectrum. Continous spectrum, a spectrum not broken by bands or lines, but having the colors shaded into each other continously, as that from an incandescent solid or liquid, or a gas under high pressure. Diffraction spectrum, a spectrum produced by diffraction, as by a grating. Emission Spectrum, an electromagnetic spectrum that derives its characteristics from the material of which the emitting source is made and from the way in which the material is excited. Gaseous spectrum, the spectrum of an incandesoent gas or vapor, under moderate, or especially under very low, pressure. It is characterized by bright bands or lines. Normal spectrum, a representation of a spectrum arranged upon conventional plan adopted as standard, especially a spectrum in which the colors are spaced proportionally to their wave lengths, as when formed by a diffraction grating. Ocular spectrum. See Spectrum Prismatic spectrum, a spectrum produced by means of a prism. Solar spectrum, the spectrum of solar light, especially as thrown upon a screen in a darkened room. It is characterized by numerous dark lines called Fraunhofer lines. Spectrum analysis, chemical analysis effected by comparison of the different relative positions and qualities of the fixed lines of spectra produced by flames in which different substances are burned or evaporated, each substance having its own characteristic system of lines. Thermal spectrum, a spectrum of rays considered solely with reference to their heating effect, especially of those rays which produce no luminous phenomena. Electromagnetic spectrum (EM): the entire range of wavelengths or frequencies of electromagnetic radiation extending from gamma rays to the longest radio waves and including visible light Mass Spectrum: the spectrum of a stream of gaseous ions separated according to their mass and charge.SpectroscopeAn optical instrument for forming and examining spectra (as that of solar light, or those produced by flames, in which different substances are volatilized), so as to determine, from the position of the spectral lines, the composition of the substance. The spectrum of an element may also be produced by exciting the electrons of the element by passing electricity through it in a vacuum. WavelengthThe distance between one peak or crest of a wave of light, heat, or other energy and the next corresponding peak or crest. “Chemical Detective activity” Identifying the elements through emission spectraJuniata College Science in MotionObjectiveStudents identify substances based on the visible spectra they emit, gaining familiarity with discrete spectra and their relationship to chemical elements.Precautions:Power Sources for gas lamps are a very high voltage. EXTREME CAUTION SHOULD BE USED TO PLUG AND UNPLUG. STUDENTS SHOULD NOT TOUCH THE LAMPS DIRECTLY. ALWAYS TURN OFF POWER SOURCE AND UNPLUG BEFORE CHANGING THE GAS BULB. The lamps should be on for minimum lengths of time to conserve bulb life. Related Subjects:AstronomyPhysical ScienceChemistryStudents should already know:Vocabulary terms aboveThat each element emits a unique wavelength of lightBasic use of a spectroscope (see directions on insert of sprectroscopes)Introduction: When you listen to the radio, cook dinner in a microwave, or watch TV you are using electromagnetic waves. Radio waves, television waves, and microwaves are all types of electromagnetic waves. They only differ from each other in wavelength. Wavelength is the distance between one wave crest to the next. Wavelength TroughCrestWaves in the electromagnetic spectrum vary in size from very long radio waves the size of buildings, to very short gamma-rays smaller than the size of the nucleus of an atom. /ems/waves3.htmlElectromagnetic waves can not only be described by their wavelength, but also by their energy and frequency? All three of these things related to each other mathematically. This means that it is correct to talk about the energy of an X-ray or the wavelength of a microwave or the frequency of a radio wave. The electromagnetic spectrum includes, from longest wavelength to shortest: radio waves, microwaves, infrared, optical, ultraviolet, X-rays, and gamma-rays. Visible light/ optical waves are the only electromagnetic waves we can see. We see these waves as the colors of the rainbow. Each color has a different wavelength. Red has the longest wavelength and violet has the shortest wavelength. When all the waves are seen together, they make white light.In a rainbow or the separation of colors by a prism we see thecontinuous range of spectral colors, the visible spectrum. A spectral color is composed of a single wavelength and can be correlated with the wavelength as shown on a EM chart. Purpose:The purpose of this laboratory assignment is to explore the visual electromagnetic spectrum using a spectroscopes and gas tubes. An electromagnetic spectrum is an arrangement of electromagnetic waves according to wavelength and frequency. To realize that each element/gas emits a unique spectrum. Identify these elements/gases by analyzing the spectrum that they emit. Realize that stars are composed of various elements, usually the lighter elements, and these can also be identified by their spectrum.Materials Overhead projector, holographic diffraction grating, and two pieces of 8” 10” dark paper; Hand-held diffraction gratings or hand-held spectroscopes; Various light sources (light sources with a long thin tube or filament are easier to view): incandescent bulb (creates a continuous spectrum); fluorescent tube (coated tubes yield a seemingly continuous spectrum); “black light” tube (uncoated tube for creating a discrete spectrum); gas spectrum tubes for different elements, include neon if possible (gas spectrum tubes create discrete spectra); and gas spectrum tube power supply; Activity Sheet A: “Visible spectra for chemical elements” (Figure 1); Activity Sheet B: “Chemical Detective” (Figure 2); Colored pencils, markers, or crayons.Safety Caution students not to touch the light sources as they may be hot and the gas tubes use high voltages. Students should not insert the gas spectrum tubes in the power supply or change the gas spectrum tubes. Students should not stare directly at the light sources for extended periods of time. Procedure1. In a darkened room, use the overhead projector, the holographic diffraction grating, and the two pieces of dark paper to project a continuous color spectrum on a wall or screen following the detailed instructions given in “The Visible Spectrum” activity on the back of The Electromagnetic Spectrum poster. 2. Ask students to describe what they see and make a colored drawing in the space provided. Students may compare the spectrum with a rainbow or with light seen through a prism or crystal. If desired, explain that the diffraction grating separates the light according to wavelength. The activity 1. Hold the hand-held diffraction gratings or spectroscopes to your eye. In a darkened room, view the incandescent source through their gratings (or spectroscopes). 2. Record observations. 3. View the sources that produce a discrete spectrum (the black light and one of the gas tubes, saving the neon tube for step 2 below). 4. Light source will be turned on around the room at various locations for student viewing. DO NOT TOUCH THEM OR ATTEMPT TO TURN THEM OFF!. 5. Draw the spectra you see and explain how the spectra produced by the black light and the gas tube differ from the one produced by the incandescent light. 6. Describe any relationship that might exist between the colors viewed in the spectrum and the appearance of the light source to our eyes (white light has all colors; black light has purple, blue, and green but not much orange or red; a hydrogen tube looks purple and has purple, blue, and red). 7. Consider electromagnetic fingerprints and discuss why they are important in identifying individual elements. Spectra are analogous to fingerprints: Each chemical element and molecule produces a unique pattern of spectral lines. This pattern of lines can be used to identify the presence of a particular element or molecule in an unknown substance. 8. Identity, illuminate the following gas tubes positioned around the room and justify your predictions. 9. Use the following chart to help you identify the spectra for the various elements and have match the lines they see from the neon gas tube to the chart. 10. Describe how you would use the previous investigation to determine what elements might be burning from the flame colors or what elements a star might be made of.AssessmentArrange students into new groups. Give each group a copy of Figure 2. Have each group work as a team to solve the mystery and submit a written report discussing their solution, the evidence they gathered that led them to the solution, and how they used spectroscopic techniques to solve the crime. Consider stressing that more than one “criminal element” was involved. Note that the “aliases” of the criminal elements are their chemical symbols, and the “perpetrators” are argon and sodium.Reinforcing conceptsThe light that we see with our eyes represents only a small portion of the electromagnetic spectrum. Developing the technology to detect and study other portions of the electromagnetic spectrum has had a tremendous impact on astronomy, where scientists must use the properties of light to learn about objects that are too far away to visit.NASA educational materials use astronomical data and the excitement of space exploration to reinforce fundamental science concepts such as the electromagnetic spectrum and motivate interest in science and technology.Assignment: Use colored pencils or crayons to complete the following assignment. 1. Draw the colors of the spectra you see in Incandescent Light2. Explain how the spectra produced by the black light and the gas tube differ from the one produced by the incandescent light. 3. Draw the colors of the spectra you see in the gas tube.4. What is your hypothesis as to the elemental gas found in the tube?5. Draw the colors of the spectra you see in the gas tube.6. What is your hypothesis as to the elemental gas found in the tube?7. Draw the colors of the spectra you see in the gas tube.8. What is your hypothesis as to the elemental gas found in the tube?9. Draw the colors of the spectra you see in the gas tube.10. What is your hypothesis as to the elemental gas found in the tube?11. Draw the colors of the spectra you see in the gas tube.12. What is your hypothesis as to the elemental gas found in the tube?13. Draw the colors of the spectra you see in the gas tube.14. What is your hypothesis as to the elemental gas found in the tube?15. Draw the colors of the spectra you see in the gas tube.16. What is your hypothesis as to the elemental gas found in the tube?17. Draw the colors of the spectra you see in the gas tube.18. What is your hypothesis as to the elemental gas found in the tube?19. Draw the colors of the spectra you see in the gas tube.20. What is your hypothesis as to the elemental gas found in the tube?21. Which of the previous element/gases would you most likely find in our Sun, a medium sized and aged star?22. Draw the probable spectrum lines for our Sun.23. What might the spectrum lines look like for a very old star, such as a red giant? 24. What would be the main element/gas of the red giant?Teachers PagePA Assessment Standards:Physical Science, Chemistry and Physics3.4.7A Describe concepts about the structure and properties of matter.3.4.7B Relaate energy sources and transfers to heat and te