So, you want to do a “Magic Show!” Student Presenter Packet for y-chem Outreach Program (10/11/2014)
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- Disposal Put the solutions into the supplied waste container. Chemistry
- For presentation Deliver 400mL beaker and bottles labeled Oscillating Clock A, Oscillating Clock B, and Oscillating Clock C. Safety
- Disposal Put the solutions into the supplied waste container. Presentation
- Dry Ice Acid/Base Indicator Solutions
- Safety Do not drink. Disposal
- Disposal Leave solid in cup. Return to LPL, and they will dispose of it. Safety
Simple ClockTwo colorless solutions are added together. After some time, the resulting solution suddenly turns blue. EquipmentTwo solutions are needed; one is labeled “Simple Clock A,” the other is labeled “Simple Clock B”. You will also want a 300-mL or 400-mL beaker. SafetySulfuric acid should always be handled with care because it is a strong oxidizing and dehydrating agent. Dilution of sulfuric acid from a concentrated form is an exothermic process. Sulfuric acid will damage clothing and skin. Sodium bisulfite is a strong reducing agent and an irritant to mucous membranes. Do not mix sodium bisulfite with acid (a toxic gas is evolved). Potassium iodate is a strong oxidizing agent and can be flammable and explosive. DisposalPut the solutions into the supplied waste container. ChemistryThe color change is initiated by a sudden increase in the number of triiodide ions (I3-) in solution when the bisulfite has been consumed. The blue starch-triiodide complex is formed in the final of four steps. IO3- + 3 HSO3- I- + 3 SO3 + 3 H+ IO3- + 8 I- + 6 H+ 3 I3- + 3 H2O 3 I3- + HSO3- + H2O 3 I- + SO42- + 3 H+ 2 I3- + starch starch- I5- complex + I- PresentationPour equal portions of Solution A and Solution B into the beaker. Tell your audience to watch closely or else they will miss the color change. The solution will change from colorless to suddenly dark blue in about 10 seconds. Oscillating ClockThree colorless solutions are added together and the resulting solution oscillates between clear, blue, and yellow. For presentationDeliver 400mL beaker and bottles labeled Oscillating Clock A, Oscillating Clock B, and Oscillating Clock C. SafetyPerchloric acid is a skin irritant. Potassium iodate is a strong oxidizing agent and mixtures with combustible can be flammable or explosive. DisposalPut the solutions into the supplied waste container. PresentationPour equal portions (100mL) of Solutions A, B, and C in to the beaker. Make sure it is in the order of A, then B, then C. The new solution will oscillate between colorless, yellow and blue. Misc. notes/PerformanceIf you don’t dispose of the oscillating clock right away, elemental iodine will accumulate at the bottom of the flask. This can be done on an overhead to allow larger classes to see the color changes. The solutions must be added in the correct order for the reaction to occur. Shaker BottlesBottles with dextrose, potassium hydroxide, and indicator change color when shaken as the indicators react with the oxygen gas dissolved into the solution. Set UpAdd two parts of solution A and 1 part of solution B into each of the 1L bottles. To the first add ~1 ml methylene blue dye ( like 2 crystals), to the second add ~0.5 ml resazurin (like 2 crystals), and to the third add a small scoop of indigo carmine. Cap the bottles. Use within about 1 hour of setting up. If solutions turn yellow, they are no longer useable. SafetyBe careful not to get indicators on clothing---they will stain. KOH is a strong base. Do not use KOH in glassware except in very dilute concentrations. DisposalDon’t leave solutions in bottles, or they will be stained and useless in future demonstrations. Put the solutions into the supplied waste container. ChemistryMethylene blue acts as a catalyst for the oxidation of dextrose by gaseous oxygen, and the other indicators act similarly. The color changes observed are due to reversible oxidation and reduction of the dyes. Methylene blue is colorless in the reduced form and blue in the oxidized form. It is thought to be reduced to the colorless methylene white by dextrose, and the shaking of the bottle dissolves oxygen into the solution, oxidizing the dye back to the blue form. If allowed to stand, the dye will be again be reduced by dextrose. Rezasurin first undergoes an irreversible reduction by dextrose to resorufin, which is fluorescent red. Then it undergoes a reversible reduction to colorless dihydroresorufin, which is readily oxidized back to the fluorescent red resorufin. The yellow color that forms after time is the decomposition products of dextrose. PresentationShake the bottles and the color changes in the following manner: Added: Change: Bottle #1 1 ml Methylene Blue Colorless to blue Bottle #2 0.5 ml Resazurin Colorless to pink Misc. notes/PerformanceKeep KOH stored in tightly capped bottles to prevent the concentration from changing. Do not allow the pre-made mixtures to stand for extended periods of time before using in the demo. Dry Ice Acid/Base Indicator SolutionsAcid/base indicators show the change in pH of a solution from basic to acidic conditions as carbonic acid is formed from dry ice. SafetyBe cautious with the dry ice, as it will burn skin. Also, be cautious with the solutions which will be acidic. DisposalPut the solutions into the supplied waste container. Leave dry ice in the supplied container and return to the LPL. ChemistryEach indicator solution starts out basic. Addition of dry ice (solid CO2) causes the formation of carbonic acid, making the solution more acidic and causing the indicators to change to their acidic color. CO2(s) + H2O (aq) ↔ H+(aq) + HCO3- (aq) ↔ H2CO3 (aq) PresentationAdd a few chunks of dry ice (broken up before presentation with a hammer) to each fleaker, and watch as the color changes. CO2 will also form at the top of the fleaker. Calcium CarbonateWhen sodium carbonate and calcium nitrate are mixed, the insoluble compound calcium carbonate is formed. SafetyDo not drink. DisposalPut the solutions into the supplied waste container. ChemistryNet ionic equation: Ca2+ (aq) + CO32- (aq) CaCO3 (s) PresentationPoint out that the solutions are starting out clear and colorless. Slowly add one solution to the other. Sodium PolyacrylateThis compound absorbs and retains as much as 200 – 300 times its mass in water, and is the absorptive component found in diapers. DisposalLeave solid in cup. Return to LPL, and they will dispose of it. SafetySkin Irritant. Avoid inhalation of the powder. ChemistrySodium polyacrylate consists of long hydrophobic carbon chains with lots of sodium ions in the middle. When you add water, it is drawn into the middle via osmosis to lessen the high concentration of sodium in the middle of each polymer. The water is then trapped within the hydrophobic carbon chain resulting in sodium polyacrylate’s ability to absorb and retain large amounts of water. PresentationAdd the sodium polyacrylate to the beaker of water and stir with the stir rod. Show to the class that the water in the beaker has been completely absorbed by the sodium polyacrylate to form a solid gel-like substance. You may also try a bit of showmanship by putting a small amount of sodium polyacrylate in a white dixie- or styrofoam cup. Take an identical cup without any sodium polyacrylate. Show the students inside the cup briefly. The sodium polycarylate will not be visible against the white interior of the cup. Put a small amount (100-200 mL) of water in the empty cup, and then pour it into the other cup. Then try to pour the water back out. 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