Beyond Labz 2.0 Assessment (3)

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Chemistry

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Jan 9, 2024

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12/11/23, 6:00 PM Beyond Labz 2.0 Assessment https://worksheets.beyondlabz.com/multiembedq.php?id=5476-5477-5478-5479-5480-5481-5482 1/5 Click here to erase all data entry on this page

12/11/23, 6:01 PM Beyond Labz 2.0 Assessment https://worksheets.beyondlabz.com/multiembedq.php?id=5476-5477-5478-5479-5480-5481-5482 2/5 Energy Levels Purpose To understand the origins of Quantum Theory using a spectrometer to observe the emission spectrum of several gases. Connections to What You Already Know About in Life Mercury vapor is used in fluorescent light tubes. The emitted visible light is not very bright for just the mercury vapor, but when scientists examined the full spectrum for mercury they saw that there is an enormous emission in the ultraviolet range (UV). This light is sometimes called black light, and you may have seen it in glow-in- the-dark displays. Fluorescent light tubes are coated with a compound that will absorb UV and emit the energy as visible light with all the colors of the rainbow. All colors together create white light which is why fluorescent light tubes emit very white light. Laundry detergents contain small amounts of a compound that absorb UV light and emit visible light. These compounds allow advertisers to claim whiter and brighter whites and colors . If you attend an event using black lights, you may have seen your white socks or white shirt “glow”. Vocabulary Emission spectrum, spectroscopy, fluorescent Background The classical picture of atoms would allow electrons to be at any energy level. According to this classical model, when electrons are excited and then fall back down to the ground state, they emit light at all wavelengths and the emission spectrum would be continuous. In the 1800s scientists found that when a sample of gas is excited by an alternating electric current, it emits light only at certain discrete wavelengths. This allowed for the development of spectroscopy which is used in the identification and analysis of elements and compounds. Even though scientists found spectroscopy very useful, they could not explain why the spectrum was not continuous. The explanation of this was left to Niels Bohr, a Danish physicist. Bohr proposed that energy levels of electrons are not continuous but quantized. The electrons only exist in specific energy levels. Because of this quantization of energy, excited electrons can only fall to discrete energy levels. You can separate the lines in the full region of an emission spectrum by using an optical prism or a diffraction grating. A spectrometer is an instrument designed to separate the emitted light into its component wavelengths and plots the intensity of the light as a function of wavelength. This assignment illustrates the measurements that helped Bohr develop his quantum model, now known as Quantum Theory. It also illustrates some practical uses for this science. Mercury vapor is used in fluorescent lights and sodium vapor in street lighting. Procedure Section 1 1. To start this activity, click this link for Energy Levels . The lab will load in a new tab. Click back to this tab to read further instructions and complete the questions below. You can follow along with the instructions below in the Procedures tab in the lab.

12/11/23, 6:01 PM Beyond Labz 2.0 Assessment https://worksheets.beyondlabz.com/multiembedq.php?id=5476-5477-5478-5479-5480-5481-5482 3/5 Questions 1. The lab table will be set up with four items. What is the detector on the right? spectrometer 2. What is the metal sample in the center of the table? W 3. A heat source is used to heat the metal sample to high temperatures. What is the temperature of the heat source? 3000 K

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12/11/23, 6:01 PM Beyond Labz 2.0 Assessment https://worksheets.beyondlabz.com/multiembedq.php?id=5476-5477-5478-5479-5480-5481-5482 4/5 Procedure Section 2 1. Click on the Visible/Full button in Live Data to change the view to the visible spectrum. Click the Save Screen button (right above the spectrometer display) to record this spectrum in the Lab Book. Open the Lab Book tab in the tray. Type tungsten metal in the Notes box and click enter. Record your observations in the data table below. 2. Click this link to load the next lab setup: Photoemission of H 2 Gas. Save this spectrum in the Lab Book. Add the note to the Lab Book that this is Hydrogen Gas. Record your observations below. 3. Open the Stockroom tab. Expand the Gases menu. Click on the Ne label to select neon as the gas and it will fill the gas sample tube. If you point to the gas sample tube it will read Gas ( Ne) . 4. Save this spectrum in the Lab Book and add a note with the name of the element typed after the image. 5. Continue with this same process until your completed samples include the following: H 2 , He, Ne, Na, and Hg. You should have five spectra saved in the lab book in addition to tungsten metal. Record your observations for each element. You can return to the Lab Book and to view any of the spectra again. Include in your observations a comparison for each element to the spectrum for heated tungsten metal. Sample Spectrum Observations W Tungsten is often associated with incandescent light sources, such as tungsten filament lamps. The spectrum is continuous and doesn't show distinct lines like those seen in line spectra. Instead it shows a rainbow range of colors H 2 visible part of the spectrum. The Balmer series is one of the most well-known series for hydrogen, featuring lines in the visible spectrum. The four visible Balmer lines are in the red, green, blue, and violet regions. He (He) has 6 distinct colored lines dark blue, light blue, indigo, green, orange, and red .Helium exhibits a rich spectrum with lines in various regions of the electromagnetic spectrum, including visible and ultraviolet. Ne with neon lights comes from the transition of electrons in neon atoms. Other lines may appear in the red, orange, and yellow regions.This has many colorful distinct Lines such as light blue, dark blue, green, light green, yellow, orange, and red Na Sodium has prominent lines in the yellow part of the spectrum. The sodium D-lines (at 589.0 and 589.6 nm) are well- known and are often seen in sodium vapor lamps. Hg Mercury has a complex spectrum with lines in the ultraviolet, visible, and infrared regions. Notable lines include the bright blue line at 435.8 nm and the green line at 546.1 nm. Mercury vapor lamps emit a bluish light due to these

12/11/23, 6:01 PM Beyond Labz 2.0 Assessment https://worksheets.beyondlabz.com/multiembedq.php?id=5476-5477-5478-5479-5480-5481-5482 5/5 Questions 4. How do your observations of these gas emission spectra help confirm Quantum Theory? energy levels in the gas s atoms or molecules. An electron transitions from one quantized energy level to another along each line, which represents a particular energy transition. The essential idea behind quantized energy levels in quantum theory is supported by this behavior. 5. What differences do you see when changing between the Visible and Full spectrum for mercury? just the mercury vapor, but when scientists examined the full spectrum for mercury they saw that there is an enormous emission in the ultraviolet range (UV). This light is sometimes called black light, and you may have seen it in glow-in- the-dark displays. 6. What distinct feature do you see in the sodium spectrum? Why do you think astronomers are excited about cities changing from normal street lights to sodium vapor street lights? lights because the emission spectrum of sodium produces fewer lines than the emission spectrum of mercury. The emission spectrum of mercury causes interference, which can make it difficult to distinguish the emission spectra of astronomical objects.