Source:<\/b>\u00a0 Shakishiri, Bassam Z.,\u00a0Chemical Demonstrations, Volume 1<\/i>.\u00a0 The\u00a0 University of Wisconsin Press,\u00a0\u00a0 Madison, Wisconsin, 1983, pp.156\u2014167.<\/p>\n
Abstract:<\/b>\u00a0 This experiment will show how luminol emits glowing light as it is oxidized by various substances, and\u00a0 to observe the same behavior in methyl salicylate crystals when crushed. **Construct the appropriate data tables in your lab notebook to record the necessary data.**<\/p>\n Procedure:\u00a0 Part A<\/b> Procedure Part B:<\/b> Questions:\u00a0<\/b>(to be answered in your lab book) 2.\u00a0 Distinguish between the energy source that provides the initial photon for the light emitted during a flame test and the source of energy in chemiluminescence and triboluminescesce.<\/p>\n 3.\u00a0 The prefix chemi\u2014 means that a _____________ _____________ produced the excited atom.\u00a0 The prefix photo\u2014 means that __________ produced the excited atom.<\/p>\n 4.\u00a0 Distinguish between the chemiluminescent process and the photoluminescent process.<\/p>\n Summary and Conclusions:<\/strong> \n","protected":false},"excerpt":{"rendered":" Source:\u00a0 Shakishiri, Bassam Z.,\u00a0Chemical Demonstrations, Volume 1.\u00a0 The\u00a0 University of Wisconsin Press,\u00a0\u00a0 Madison, Wisconsin, 1983, pp.156\u2014167. Abstract:\u00a0 This experiment will show how luminol emits glowing light as it is oxidized by various substances, and\u00a0 to observe the same behavior in methyl salicylate crystals when crushed. Introduction:\u00a0 Many combustion reactions produce light by thermal means. These […]<\/p>\n","protected":false},"author":3,"featured_media":0,"parent":169,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"footnotes":""},"class_list":["post-184","page","type-page","status-publish","hentry"],"acf":[],"yoast_head":"\n
\nIntroduction:\u00a0 Many combustion reactions produce light by thermal means. These reactions release sufficient thermal energy to heat the reaction mixture to\u00a0 incandescence.\u00a0 Other reactions release energy at room temperature.\u00a0 This exothermic production of visible light by a chemical reaction is called chemiluminescence.\u00a0 When a reaction of this nature occurs in living organisms, it is called bioluminescence.\u00a0 The most familiar example of such an organism is the firefly.\u00a0 In a biochemical reaction within the body of this insect, light is produced by the action of an enzyme on the substrate luciferin.\u00a0 Other organisms producing bioluminescence are certain bacteria, algae, coelenterates (the sea pansy) and crustaceans such as the cypridna.\u00a0 Chemiluminescence occurs when an energy\u2014releasing reaction produces a molecule in an electronically excited state and that molecule, as it returns to\u00a0 the ground state, releases its energy as a photon of light.\u00a0 Lightning exemplifies gas\u2014phase chemiluminescence.\u00a0 When an electrical discharge occurs in the atmosphere, gas molecules, such as N2<\/sub>\u00a0and O2<\/sub>\u00a0are excited from the ground state to higher energy levels.\u00a0 In addition, N, O and other atoms are produced.\u00a0 The recombination of these atoms into molecules, as well as the return of\u00a0 excited\u2014state molecules to the ground state, releases energy in the form of visible light.\u00a0 Chemiluminescence also occurs in the liquid and solid phases, as illustrated by the following laboratory procedure.
\nThe chemiluminescent process is distinctly different from the photoluminescent processes fluorescence and phosphorescence, both of which occur after the excited state of a molecule is produced from its ground state by the absorption of light energy. Thus fluorescent species emit light only while being irradiated.\u00a0 Phosphorescent species may appear to emit light without being irradiated, but this emitted energy had to have been absorbed at an earlier time.\u00a0 Chemiluminescent reactions, however, produce light without any prior absorption of radiant energy.
\nAnother phenomenon known as triboluminescence is the emission of light energy when a mechanical stress is applied to a crystal.\u00a0 As the crystal is stressed by applying pressure or torque. This phenomena is explored in Part B.
\nMaterials:<\/b>
\n2\u00a0 400 mL beakers (for mixing solutions A and B)
\n1\u00a0 250 mL beaker\u00a0 (the reaction vessel)
\n2\u00a0 25 or 50 mL graduated cylinders (for measuring solutions A and B)
\n1\u00a0 10 mL graduated cylinder\u00a0\u00a0 (for the 3% H2<\/sub>O2<\/sub>)
\nSolution A:\u00a0 prepare by dissolving approx. 0.1 g. luminol and 1 g. NaOH in 250 mL water.
\nSolution B:\u00a0 prepare by dissolving 2.5 g. K3<\/sub>Fe(CN)6<\/sub>\u00a0 (potassium ferricyanide) in 250 mL water, then adding
\n5 mL 3% H2<\/sub>O2<\/sub>(hydrogen peroxide).
\nA pinch of fluorescein\u00a0 FIGURATIVELY SPEAKING \u2014 DO NOT TOUCH!!!
\nA few drops of phenolphthalein solution (in dropper bottles – please share nicely!)
\nA few pieces of wintergreen candy (methyl salicylate crystals)<\/p>\n
\n1.\u00a0 Carefully make solutions A and B as directed.\u00a0 Label the beakers. When you are finished, let your instructor know that you are ready for lights out.\u00a0 You have enough of the solutions to repeat a step if\u00a0 you want.
\n2.\u00a0 Measure equal amounts of each solution ( about 25\u201450 mL each)into the graduate cylinders.
\n3.\u00a0 Simultaneously pour the solutions into the third beaker and swirl it gently.\u00a0 Record your observations. (Oooohhh, aaaahhh!)\u00a0 Dump the solution ( save a bit in a test tube if you wish) and rinse the beaker well.
\n4.\u00a0 Add a pinch of fluorescein to about 20 mL of water in the beaker, then repeat steps 2 and 3. Record your observations.\u00a0 Dump and rinse out the beaker.
\n5.\u00a0 Put 20 mL water in the beaker and add a few drops of phenolphthalein.\u00a0 Repeat steps 2 and 3.\u00a0 Record your observations.
\n6.\u00a0 Clean up and be sure to wash your hands well.<\/p>\n
\n1.\u00a0 Get a few pieces of life savers and go to a dark corner with your\u00a0 lab partner\u00a0 (!!!!!!!)
\n2.\u00a0 Holding the candy between your teeth or in a pair of pliers, bite down hard while your partner watches carefully for tiny flashes of blue light.
\n3.\u00a0 Record your observations.<\/p>\n
\n1.\u00a0 Define:\u00a0\u00a0 a.\u00a0 chemiluminescence.
\nb.\u00a0 bioluminescence.
\nc.\u00a0 triboluminescence.
\nd.\u00a0 phosphorescence.
\ne.\u00a0 fluorescence<\/p>\n
\nWrite a paragraph describing what you observed.<\/p>\n