edited bv
GEORGE L. GILBER? Denison University
tested demonstrcrtions Adding Colors and Sparkles to Hydrogen Balloon Explosions John J. Fortman Wright State University Dayton. OH 45435 One of the most frequently used, a s well a s one of the most dramatic, demonstrations is the explosion of hydrogenfilled balloons. However, if one uses only demonstrations related to the topic being covered in class there are only a limited number of topics&uch a s gases, combustions, re&tions, and thermochemistry) to which the explosions can be related. Even in shows done strictly for entertainment the explosions may become monotonous if done too often. By a simple modification one can add variety to a series of explosions in a demonstration show or use the explosions while discussing emission spectra and electronic energy levels (a topic with few classroom demonstrations). HydroBased on part of a paper, "Some Simple Modifications of Some Classic Demonstrations,"presented at the 10th Biennial Conference on Chemical Education, Purdue University, IN, August 3, 1988.
Granville, OH 43023
gen balloon explosions with colors and sparkles added are very effective for large demonstration shows in auditoriums, gyms, or out-of-doors. 'Safety Note: I n smaller rooms, especially, avoid using a large excess of salts or metals. Avoid igniting the balloon without combustion of the solid, to prevent fonnationof aeoncentrationof invisibledust particles in the air that can cause coughingor other irritations.
Flame Test Demonstrations There have been a number of recent telling ways to demonstrateflame tests to large classes (1-7). This can he done more easily and more dramatically by simply adding a teaspoonfid of a solid salt to a balloon (size no. 14 round) before inflating it with hydrogen to a diameter of about 30 cm. A scoopula is useful for pouring the solid into the balloon. Caution: When putting hydrogen gas in balloons that contain salts or metal powders, safety glasses o r a face shield must be worn. When a balloon pops, solid particles are thrust out in all directions and these could be serious irritants to the eyes.
Solids and the Effect on Hz Balloon Explosions Solid
Effect
Approximate Amount (fora 30-crn balloon)
Sr(N03)z
bright red
1 tsP. (4-6 g)
LiN03
pale red
1 tsp. (15-25 g)
Ca(N03)~4HzO
orange
1 tsp. (3.55.5 g)
One of the best effects Better than CaCIz, but still difficult to distinguish from yellow-orange of Hz alone Cannot be distinguished from Hz alone
yellow green
Comments
Somewhat faint but or better than Ba(N03)z
1 tsp. (3-5 g) 1 tsp. (1-2 g)
blue
1 tsp. (2.54 g)
One of the best effects; other Cu salts may give a more greenish tint
KC1
pale violet
1 tsp. (2-4 g)
faint color
RbCl
violet
1 tsp. (2-3 g)
better than KCI, but expensive
CSCl
violet
1 tsp. (1-2 g)
best violet, but most expensive
Fe powder
gold sparks
0.5tsp. (5-8 g)
One of the best effects;can be mixed with a salt for combined effect
Mg powder
silver sparks
1 tsp. (1.5-2.5 g)
One of the best effects
Al powder
bright white flash
1 tsp. (2.5-4 g)
Very bright
Volume 68 Number 11
November 1991
937
When tied in place the solid settles to the bottom of the floatineballoonamund thestem.andifthetlarne is broueht up to th;ltpomt the resulting exp~osionnwill~keon theczor of the flame test. Copper(I1) chloride gives a nice blue and strontium nitrate produces a bright red. Other salts can be used to give averitable rainbow ofcolors, but, ofcourse, one must not use salts of metals that are toxic. I n the table are listed some solids producing the best colors. Comments on the results and expense of other salts are given in order to spare users the efforts of t r d ineffective substances. interestingly the anion sometimes may affect the shade or the intensity, and hydrated salts often give superior results. Some of these~salts,a s for instance those of barium, may be harmful or toxic if ingested or inhaled in large enqugh doses (81,but in the very low concentrations that would be present when the explosions are done properly outdqors or in a large, well-ventilated room the exposure should be well below those limits. Lists of flames tests can also be found in manv freshman texts and in some of the earlier referenced articies (1,3-5). To determine the optimum amount for the size of balloon used it is best to experiment with different quantities. Too large a u amount mav produce a shower of solid particles or, if tLe mom is not adkquately ventilated, unpleasant fumes powmay be experienced. Also the solid should be finely ~. dered, to minimize unreaded salt in the air. In addition to adding colors for demonstration shows with salts, powdered metals will give a sparkler .effect. Iron powder (40-100 mesh) makes golden sparks and magnesium (40-80 mesh) or aluminum ~ o w d e rproduces silver sparks ,Y,IO .Again the amount t o k e is about a teaspwnful fbr a size 14 halloon and is best determlncd by trial and error for the sire balloon used. A large excess in this case will k c e the ~ balloon from floating. As with the salts the demonstration should be done in a large,well-ventilated room or outdoors, because unpleasant fumes may be produced. However, these exp6sions have been done frequently in auditoriums and gymnasiums without unpleasant fumes, provided too much solid was not used; the flame was brought up to the solid in the balloon for proper ignition; and the air flow in the room did not carry any smoke produced to the audience. Prior to using the solid salts. solutions of the salts were tried but the water apparentli dissipates too much of the heat from the explosions to allow the production of colors. I t is important that the flame be bmuiht up to the base of the floating balloon to make immediate contact with the solid in order togetgood colors, but if you are not careful the tethering stringmay be burned through releasing the balloon to float away. With these simple demonstrations can add very little interest to your lectures on the electronic structure of atoms where there are few demonstrations from which to choose. They are even more effective in adding color and variety to your demonstration shows.
Literature Cited 1. Peyser, J. R.; Luoma, J. R. J Chem. E d u c 1988.65, 4 5 2 4 3 .
2. Gouge, E. M. J Cham. Educ. 1988,65,54&545. 3. Ager,D.J.;Ea&,M. B.; Miller,R. A. J. Chon. Edue. 1988.65. 545.
Triezonberg. H.; Ch%atian,T.: Marek, L., paper no. 286 at the 10th Biennial Conferencean Chemical Education. Pvrdue University. IN. Augvst 3. 1988. 5. Pearson, R.S. J. Chom. Educ 1988.62, 622. 6. Stmng, F. C,nI.J Chem Zdue 1969.46, 178. 7. M a l e . C.; Bruno, P. J C h r m Edur. 1976.53,731-735. 8. Gosselin, R. E.; Smith, R. P.: Hodge, H. C . Cliniml Tmiedogy of C o m m z ; o l Pmduels. Sth ed.: Williams & Wilkens: BaltimoreLondon, 1984. 4.
938
Journal of Chemical Education
Spontaneous Detonation of a Mixture of Two Odd Electron Gases Submitted by Thomas S. Briggs Lowell High School San Francisco, CA 94132 Checked by
Daniel Haworth Marquette University Milwaukee, WI 53233 Three familiar odd-electron molecules (NO, NOz, and C102) have a positive heat of formation. These molecules have a significant tendency to interact; for example, NO2 + NO2 gives Nz04and NO + NOz gives N203.I n fact, it seems likely that the reaction of C102 with NO "is the fastest known reaction between two stable molecules a t room temperature"'. The reaction of these gases in the upper atmosphere is of great interest to chemists studying the fate of our ozone layer (C102 is usually written OClO by atmospheric chemists). Typical papers are inscience, 1988, 242, 558 or Nature, 1988,332, 796. When the gases ClO2 and NO are mixed a t standard pressure and temperature conditions a detonation occursa that illustrates ihe high reactivitv of chemicals which are normally stable. This rksult suggests that a reaction product such as NOC102 rapidly decomposes a t room temperature. Only NO2 and C10 can be detected when ClOz and NO react under controlled conditions a t very low pressures.' The detonation of C102 and NO c a n be safely demonstrated by conducting the following experiment on a very small scale in well ventilated area. Safetv precautions for this demonstration should include eye goggles and gloves for the demonstrator and safety shields in place. The demonstrator should practice the detonation a t a distance (by addingabout 5 mgofNaNOzfrom a scopula attached to the end of a meter stick when doing the last step i n the procedure) and scale the demonstration down if it is too loud. A heavy walled 10-mL test tube wrapped with clear cellophane tape is the largest glass container that should be used, and the demonstrator should be sure goggles and gloves are worn. About 0.1 g of sodium chlorite is placed in the test tube and one or two drops of concentrated hydrochloric acid are added to the NaC1O2. The test tube then fills with thedeep yellow color of CIOZ,~ whichiseasily seen by a group of students about 20-30 in class size. 5HC102+ 4C10, + Cl-+ Hi+ 2H20
-.
When the gas evolution stops a tiny amount of NaN02 (less than 5 mg) is cautiously added to produce the NO. An immediate detonation occurs, which can be heard in the back of a large room. The color due to the C102 vanishes. These small amounts of relatively nontoxic chemicals can be flushed down the drain. Since acidified NaN02 yields both NO and NO2 2HN02 +NO + NOz + H20 separate experiments are needed to show that only NO is reactive. when each nltrogen ov~de1s tested w ~ t ha-sample of safely diluted CIOl about 60 mm partlal pressure 'only the NO-bleaches thecolor of the ~ 1 0 ~ .
' Coxon,, A . Trans
Faraday Soc ,1968. 64.2118 Ra~scherW C mpJb sneo dara Keefer.R G .Gordon G Inorg CCnem 1968 7, 239 Cotton, F. A,; Wilkinson, F. R . S . Advancedlnorganic Chemistry 3rd Ed.; Wiley: New York, 1972: p 473.
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