Tested Overhead Projection Series
Ill.&!..m
Compiledby
HUBER T N. Al YEA Princeton University
Dem. 7 53-Surlac e Tension
24. MISCELLANEOUS Dem. 7 49-Dense
Liquid
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Suggested by A. Wiswanathan and S. Gireesan, Madras India. Preparation of K2HgI2. Stir 65 g of KI + 7 5 g of Hg l 2 with 15 g H20. Pilter. A yellow solution of K2HgI 2 forms, density 3.19 at 230°0.
Procedure: Project in C-2, showing bits of marble, glass, and quartz (about density 2.5) sink in water but float on this denser liquid. Dem. 750-Detergenl
Action
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To show: Lowering of surface tension by a detergent. Materials: Petri dish, pepper, detergent. Procedure: Project w~tte r in a petri dish on the horizont a l stage . Sprinkle in a little pepper. Put one drop of detergent in the middle of the pepper.
Observations: The pepper sud denly is forced back towards the side of the dish. Dem. 751-Surface
Tension
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Devised by R. C. Pura, Princeton (1969). To show: Surface effects on a water-filled container. Materials: Plastic box 3 X l1/ 2 X l1/2-in. Two small
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Suggestedby Paul Fall. To show: Formation of globules due to surface tension . Materials: NaCl, ortho-toluidine, 45 mm watchglass, methylene blue.
Procedure: Project the watchglass containing 2 ml N'aCl-aq tinted with methylene blue. Add some drops of ortho-toluidine .
Observations: Globules form on the surface of the water. Dem. 754-Volume
on Mixing
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Suggestedby Fr. Luci.en R. Donnelly. Materials: 30 ml of beads 1 mm diameter; beads 2 mm diameter; C-3.
30 ml of six 13 X 100 ml test tubes.
Proceditre: Project the six tubes in C-:3. Fill, to exactly the same height, tubes 1, 2 and 3 with 1 mm beads; and tubes 4, 5, and 6 with 2 mm beads. Call attention to these equal volumes . Now mix tubes 1 + 2, 3 + 4, and 5 + 6.
+ 2 and 5 + 6 are + 4 form a volume
Observations: Tubes l volume, but tubes 3 less.
at the same about IO%
corks.
Note: Compare the same result when absolute ethyl alcohol and water molecules are mixed (See Dem. 236).
Procedure: (a) Project the box half-full of water; drop in two corks. (b) Add water gradually until it
What conclusion do you reach regarding the relat ive molecular size of these two liquids'?
fills the box to the brim .
Observations: (a) The corks in the half-filled box are pulled to the sides. (b) When the water reaches the top of the box, the corks are pulled together in the center of the curved water surface. Dem. 7 52-Polar Attraction
scs
Suggestedancldevelopedby C. A. Sloat, GettsburgCollege (1965).
To show: Attraction of -COOH
in oleic acid towards
Dem. 7 55-Solubilit y of Iodine
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Suggesleclby D.S. Evans. To show: Relativ e solubiliti es. jJf alerials: CCI 1, ether, iodine, KI-aq; 2-oz. widemouth, square, glass bot t le.
Procedure: (a) Project bottle; add 1/a \\'ater + 1/a CCLi + 1/ 3 ether in that order, noting the position each aF;sumes. ~ ow drop in a few flakes of iodine. (b)
water.
Repeat , using Kl-aq in place of water.
Materials: 15-cm petri dish, droppers, detergent, talc
Observations: (a) The depth of color ,vill indicate the relativ e solubilities of iodine as it sinks through each lay er. (b) E.I-aq forms brown Eia.
or lycopodium powder in a salt shaker with top covered with a layer of cheesecloth; paraffin oil, oleic acid.
Procedure: Clean 1,hepetri dish with detergent . Project dish half-filled with water. Dust talc lightly over its surface, then add a 3-cm pool of paraffin oil to its center. To the middle of the pool add one drop of oleic acid.
Observations: In a few seconds the oleic acid pene trates the oil; the talc and oil are explosively pushed away as the -COOH of the oleic acid is attracted to the -OH of the water.
Dem. 7 56-Crystal
Models
SD 1
Sur1gestedbyFr. Lucien R. Donnelly, O.S.B. M aferials: 40 mm (no larg er) watchglas,-, lead shot 2 mm diameter.
Procedure: Pour lead shot (first 10, then :20, then 40 shot) upon the 40 mm watchgl::tf;S011 horizontal stage. Rock the watchglass, observing patterns. Volume 47, Number 4, April 1970 / A333
Observations: Beautiful geometrical shapes form. The optical illusion suggests X-ray diffraction, dislocation, vaporization, etc . Note: This imitates the crystal face patterns achieved by E . i\liller's emission microscope.
J1laterials: ZnS0 4·7H20 ; small spatula; FeCls · 6H20;
microscope slide.
Procedure: Project three piles of equal size : one the zinc salt, another the ferric salt, and the third a mixture of equal volumes of the two salts ground together . Observation : Th e mixture liquefies.
Dem. 7 57-Goniometric
Patterns
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Suggestedby Fr. Lucien R. Donnelly, O.S.B. Project against a piece of paper on which a base line has been drawn. Place a crystal so one edge lies along this line, and draw a crystal face angle, sta rting from this base line. Choose anot.her face, and repeat. Complete the figure.
Dem. 7 SB-Crystallizing Hypo
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Fr. Litde:n R. Donnelly, 0.S.B. sugyests the following variatfonof Dem. 861. Heat excess hypo crystals on a 4 X 4-in. glass plate until just melted; place inside a discardable magazine on about page 10. Heat a second glass plate well above the mp of hypo, pres;:,upon the crystals, melting them completely. Close the magazine, squeezing some fused salt out. Shift the glass-hypo-glnss sandwich to another ten pages and squash again. By now the hypo begins to crystallize at the edges of the glass plate. Place the sandwich between two polaroids at 180° on the projector, and switch on the lamp . Apply wet to"·els to hasten cooling. Focus sharply.
Nole: A thermocouple reading may be projected during the cooling process. Dem. 7 59-Double
Crystallization
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.Su{J{Jesled by Fr. Lucien R. Donnelly, 0.S.B. See Dem . 758. :\Jake a double-decked sandw ich; melt with a propane torch; cool one side from the edges until solidific1c1tion begins. As a ring of colors close towards the middle, they are joined by another ring. The result is a beautiful, startling, complex double effect.
Dem. 760-Chemical
Whiskers
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Suggestedby Bruce Dinsmore (1940). Materials: SatUI'ated Al(N03)a-aq; glass.
Reference: 312(1938).
YAMASAKI,
T. K.
and
K.,
Kolloicl Z ., 84,
Dem. 762-Subliming As2Sa
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Suggestedby M. B. Celap,Belyrade, Yugoslavia. Procedure: Project a culture tube containing a small amount of solid As2S3in H-3 over a burner. Observation: Sublimation, without melting, occurs. Dem. 763-lonic
Reaction :
Hg++
+ Al
6A 1
To shou:: Reaction in water but not in hexane. Materials: Two culture tubes, C-3, HgCl2 powder, clean a.luminum wire, hexane. Procedure: Project culture tubes with 1 g I-IgCl2 in each. Add 5 ml hexane to tube 1, and 5 ml water to tube 2. Shake. Insert Al wire. After a while add \\'ater to the hexane, shake and insert Al st rip. Observations: Rapid reaction in water solution only . 3Hg+ + + 2Al - 3Hg + 2Al+ ++.
Dem. 7 64-pH
Change during Electrolysis
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llfaterials: Very dil. HJ,04, brom-cresol green, electro lysis apparatus as in Dem. 3; 6 v de. Procedure: Same as in Dem. 3, but electrolyze a solution containing some drops of brom-cresol green plus sufficient acid to give a green color to the indicator. Observations: Dur ing electrolysis, the solution around the positive pole becomes more acidic and the indicator turns yello"·; around the negative pole the solution becomes more basic and turns blue. Note: Brom-cresol green is yellow below pH 4, green between pH 4 u.nd 5, blue above pH 5 (approximate pH's).
aniline, watchDem. 765-Electro/ysis
Procedure: 1\Iix equal volumes on a watchglass on the horizontal stage . Project. Observations : A gel forms; from it, hairlike crystals of aniline nitrate grow in about five minutes.
of Hg{N0 3) 2
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From the ChicagoWorlcl'sFair (1932). Materials: C-3, Hg(N0 3)2-aq, 6 v de, electrolysis apparatus . Procedure: Fill the plastic tube electrodes and middle cell of C-3 with Hg (K0 3}2-aq. Project. Electrolyze.
Dem. 761-Liquefaction
on Mixing Salts
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Suggestedby T. Yamasaki, 1'okyo, Japan . To show: Liquefaction caused by tituration of solid hydrated salts. A334 / Journal of Chemical Education
Obse1-vations:Oxygen gas is evolved at the positive pole; droplets of Hg form on the negative pole. To show the droplets, it may be necessary to remove the wire from the solution and bring the droplet5 into sharp focus.
