Observing Metallic Salts When put into a Flame to Identify the Unknown Metal.
Ava BarryDecember 12 – December 13, 2017Lab Partners: Adeline Dornik, Kit Piper-Hauswirth, Madison DillonPurposeThe purpose of this lab is to find the unique color of light emitted by the metals; calcium, copper, lithium, potassium, sodium,and strontium when they are heated in a flame. By observing the reactions of metallic salts when put into a flame identifying the unknown material will be possible. This lab introduces how color is shown through light.
TheorySome important words relating to this lab are electrons, orbitals,ground state, and energy levels. Negatively charged subatomic particles are called electrons. Electrons travel in pairs and move in regions of space around the nucleus in orbitals.
The central part of an atom is called the nucleus and it that has both neutrons and protons. The energy level is lower when the electron is closer to the nucleus. The energy level rises when the electron is in an excited state and jumps orbitals. As the electron is farther away from the nucleus the energy level increases(Chapter 6).
The release of energy takes the electron back to ground state. The distance between the crests of an electromagnetic wave is called the wavelength, and the number of wave cycles that pass a given point per second is the frequency (Pearson).Atoms that absorb energy and have electrons that move to higher energy levels are referred to as Electromagnetic Radiation, these electrons lose energy by emitting light when they return to lower energy levels (Pearson 151). Extra energy occurs when the electron jumps from its original state to the excited state. Excited state is a quantum state that has a higher energy level than ground state. When heat is introduced excitement causes electrons in the atoms to have extra energy. Particles representing a quantum of light are called photons, they are packets of energy carried along in electromagnetic waves.
Only a small part of the light electromagnetic radiation is able to be seen and that is called visible light. The amount of energy in photons has a direct correlation to the frequency of the electromagnetic radiation(Pearson) The formula to find the energy in joules is: Formula 1: C =??In this formula “C” is the energy, “?” is wavelength, and “?” is frequency. The wavelength of a wave is determined by the velocity and the mass of a particle. In order to find the wavelength of a particle the formula needed is: Formula 2: ?E= hc / ? This formula is used for h is Planck’s constant (h= 6.626 x10-34 J sec) c is the speed of light (c= 2.998 x 108 m/sec) The change in energy and relating it to finding the speed of light is found by using this formula.
Methods utilized in this lab are as follows, Noting the color that is produced from the substance in the flame using a spectroscope, documenting descriptive observations and calculating wavelength, frequency, and energy. The second day the metal salts will be nameless and using the observations from day one figure out which metals are which.MaterialsCalcium Chloride, CaCl2.2H20, 1-1.5gCupric Chloride, [email protected], 1-1.5gLithium Chloride, LiCl, 1-1.5gPotassium Chloride, KCl, 1-1.
5gSodium Chloride, NaCl, 1-1.5gStrontium Chloride, SrCl2.6H20, 1-1.5gWater, distilled or deionized, 250 mL2 Beakers, 250 mLLaboratory Burner6 Watch Glasses or weighing dishes6 Wooden Splints soaked in waterSafetyCupric chloride is highly toxic by ingestion; it is necessary to avoid contact with eyes, skin, and mucous membranes.
Lithium Chloride is moderately toxic by ingestion and can cause irritation to exposed tissue. Extra care is needed to fully extinguish the wooden splints by submerging them in a beaker of water before disposing of them in a trash will avoid fires. Wear chemical splash goggles, chemical-resistant gloves, and a chemical -resistant apron.
Wash hands thoroughly with soap and water before leaving laboratory.ProcedurePart 1 of ProcedureFill a 250 mLbeaker about half way full with tap water. Obtain six wooden splints that have been soaked in tap water. Place them in this beaker to continue soaking at your lab station.Fill a second beaker about half full with tap water. Label this “rinse water”Label six watch glasses “CaCl2”, “CuCl2”, “LiCl”, “NaCl”, “KCl” and “SrCl2”. Place a small scoopful of each metallic solid in the corresponding watch glasses.
Light laboratory burnerDip the soaked end of one splint into a salt, then place in flame, observe the color of the flame. Look through the spectroscope. Allow the splint to burn until color fades. Try not to let any of the solid fall into the burner’s barrel. If necessary repeat the test with the same splint and salt. Record observations Place the wooden splint in the “rinse water” to fully extinguish it, then discard in trash. Repeat steps 5-7 for other five salts and record. Part 2 of Procedure Acquire one wooden splint that is completely soaked in tap water.
Dip a soaked end of the wooden splint into unknown salt, then place in flame. Observe the color of the flame. Look through spectroscope. Allow the splint to burn until color fades.
If necessary repeat the test. Record observations to see if the new data of the unknown substance matches any known substances from the previous data. Place the wooden splint in the “rinse water” to fully extinguish it, then discard. Repeat steps 1-4 for other five salts and record. Data and CalculationsObservationsTable 1: The Electromagnetic SpectrumRepresentative Wavelength (nm) Wavelength Region (nm) Color410400-425violet470425-480blue490480-500blue-green520500-560green565560-580yellow-green580580-585yellow600585-650orange650650-700redTable 2: Color of the Flame when the known salts were burned.
Metal Color of FlameCacl2OrangeCucl2Green KclVioletNaclOrangeSrcl2Orange/ RedLiclRedTable 3: Color of the Flame when the unknown salts were burned.Metal Color of FlameX VioletZOrangeA GreenC RedB Orange/ RedY OrangeTable 4: Using observations and calculations from known salts and comparing them to the unknown metallic salt to come to the conclusion of which letter goes to which metal.Metal LetterCacl2X Cucl2ZKclA NaclC Srcl2B LiclY Table 5: Observations and calculations taken from testing different metallic salts in a flameMetal Color of Flame?(nm)?(m)?E (J)Cacl2Orange6006.0x10-73.
31×10-19Cucl2Green 4904.9×10-74.05×10-19KclViolet4104.1×10-74.84×10-19NaclOrange6006.0x10-73.31×10-19Srcl2Orange/ Red6506.
5×10-73.05×10-19LiclRed6506.5×10-73.05×10-19CalculationsThese calculations correlate with the data in Table 5:Conversion of nm to m:(600nm/1)x(1m/1×10^9nm)=6.0×10-7m?E= E photon (J):?E=hc/??E=((6.
31×10-19DiscussionThe goal of the lab is to identify the unknown substance by exposing it to a heat source and then observing the reaction and comparing it to the known metals reactions. The main purpose is to match the findings of day one to the findings of day two connecting the known and unknown substances. During the first part of the procedure, calculations and observation show that ? (m) ranged from 4.1×10-7 to 6.5×10-7and ?E= E Photon (J) ranged from3.05×10-19 to 4.
84×10-19. The colors violet, orange, green, red, orange/ red, orange were observed during the experiment. The group found that metal Cacl2 was X, Cucl2 was Z, Srcl2 was B, Kcl was A, Nacl was C, and Licl was Y.When testing an unknown salt in part two of the procedure, the conclusion of the calculations show the unknown salt as “CaCl2”. This statement is proven because the predicted ? in nanometers was 600 and the color of the flame was orange. This correlates to the Electromagnetic spectrum and when compared to “CaCl2” in part one of the experiment. By taking a wooden splint and rotating it in a metallic salt and then placing it over the flame and the color of the flame transition is observed. The CaCl2 salt appears an orange color which means that wavelength jumped to a higher energy level and when the electron dropped back down the extra photon is released in the form of a visible orange flame.
Frequency, wavelength and energy are all related because the greater the energy, the larger frequency and the shorter wavelength. The higher the energy is shown in the graph, as well as the shorter the wavelength. While higher the energy the higher the frequency. This experiment has some restrictions in part one, it is possible that some contamination happened because of the wet wooden splint being used in multiple salts. This could be improved by using separate water containers each time a stick is submerged and not reusing the sticks. This experiments accuracy could also be improved by ensuring all calculations are as accurate as possible by retesting a salt in the flame and comparing observation notes. The last improvement could be made by testing the salt on a bigger or smaller flame to determine if the color is more or less prominent. The extension of the experiment, including more observation and repeating the calculations based on testing a bigger flame or smaller flame will reduce the error of identifying the incorrect salt.
The possible purpose of extending the experiment could be the use of colorful flames outside of the classroom for entertainment purposes, such as with fireworks (Bryner). By better understanding how the size of the flame effects the color change and could show more specific colors during the explosion could help make more spectacular fireworks in the future.