The following lecture demonstrations are available from Chemistry & Biochemistry Teaching Laboratories, York 3150.
Chemistry & Biochemistry Instructors may schedule the materials needed for a class by contacting Peter Wotruba by electronic mail.
A minimum of TWO (2) DAYS ADVANCED NOTICE is required.
Instructions for performing the demonstrations will accompany the chemicals and glassware that are delivered to your classroom.
Balloons are filled with hydrogen gas, attached to a clamp holder by a string, and ignited with a match taped to a yard stick.
2. Charles' Law
Balloons are filled with oxygen and helium and show a decrease in volume when immersed in liquid nitrogen.
A green, aqueous solution of nickel nitrate becomes deep blue on addition of ammonia, purple on addition of ethylene diamine, red on addition of dimethylgyloxime, finally yellow on addition of KCN.
Sealed glass tubes containing reddish-brown nitrogen dioxide are placed in hot water and on dry ice and become darker brown or colorless, respectively.
A pink, aqueous solution of cobalt(II) hexahydrate becomes dark blue when concentrated HCl is added, then pink when diluted with more water. Color projects best on an overhead projector.
A pink, aqueous solution of cobalt(II) hexahydrate becomes dark blue when heated with a torch. When the bottom of the test tube is placed in ice water, that part turns pink, while the top remains blue.
A small pellet of sodium is dropped into a glass dish of phenolphthalein solution on top of an overhead projector. Red trails are produced as the sodium travels across the dish. Can do lithium and potassium to demonstrate increasing reactivity.
A flask containing a yellow solution of ammonium vanadate is poured into a flask containing zinc amalgam. With shaking, solution turns yellow to green to blue to purple. Vanadium can be reoxidized with cerium sulfate. Colors project well in petri dishes on an overhead projector.
An analog meter with a 30-cm scale is connected through an amplifier to a pH meter and a glass electrode.
A large voltmeter may be used to measure the reduction (half-cell) potentials of Zn, Cu and Pb.
An electrochemical cell is constructed from Cu and Zn half-cells and connected via a balogna salt bridge.
Hot and cold packs are passed around the class. Students can note the temperature change.
Mix equal volumes of prepared solutions on a stir plate, solution oscillates between dark blue and clear/yellow. Last about 15 minutes.
A polyvinyl alcohol solution mixed with a sodium tetraborate solution and food coloring produces a colored polymer that flows and can be shaped; it will sheer if twisted quickly.
Equal volumes of prepared solutions, mixed on a stir plate with ferroin indicator, give a solution that oscillates from green to violet to red to blue and back to green. Lasts about 30 minutes.
Three premeasured solutions are mixed, stirred until the bromine color disappears, and ferroin indicator is added. The solution is poured into a petri dish on an overhead projector to cover the bottom with a thin (~1-mm) layer. Oscillations will start. Refer to the March 30, 1987 issue of C&E News for the original article.
This is another variation of the Belousov-Zhabotinsky Oscillating Reaction. It is a bit more reliable than the other variation, but it can not be premeasured and premixed.
Magnesium filings are pour into a cavity in a dry ice block and lit with a hand held torch. Another dry ice block with an identical cavity covers the burning magnesium. Dim the lights and the class can see the Mg burn between the dry ice blocks.
16. Light Sticks
Cyalume light sticks can be used to demonstrate how temperature affects reaction rate. Put one light stick in hot water and one in ice water. Dim lights and compare luminescence with room temperature light stick.
A basic glucose solution with methylene blue as a redox indicator turns blue when shaken, then reverts to clear on standing. Repeats through 15 shakes.
Hydrogen peroxide is catalytically decomposed with KI. A drop of soap is added before the KI so the oxygen released during decomposition produces foam.
Demonstrates the Meissner effect, where a magnet will float above a material in a super-conducting state.
Reproduces molecular behavior in gases, liquids and solids using small balls on an overhead projector. Turns abstract Kinetic Theory concepts into visual images, easily understood.
Shows the color spectra of white light and the spectral lines of neon. Diffraction gratings (~1in2) are passed out to the class, room lights are dimmed, and the class views light from an incandescent light and a neon discharge tube.
This demonstration shows the differences of different salt solutions when burned. Cotton balls soaked with the salt solutions are burned and produce a different color flame. Diffraction gratings may be used to see the differing spectra of the salts.
Acetylene is generated with calcium carbide and HCl and ignited with bleach. Generates an explosion with flameball.
Ferric oxide and aluminum powder are ignited with an Mg fuse in clay flower pots. Molten iron drops from the pots into a dish of sand.
Show acidity changes using universal indicator, dilute NaOH, and dry ice; pH changes as CO2 dissolves in water to form carbonic acid and sodium carbonate. Explain buffer solutions as the color change slows.
One liquid is added dropwise to another, forms a precipitate. Can be done with precipitates of different colors. Views nicely on the overhead projector using large well plates, but the color of the precipatates doesn't project. Large flasks show colored precipatates well for large lecture halls.
Check solutions and solids for conductivity using an apparatus that includes an incandescent lamp and an inert gas lamp in the circuit. Salts, sugars, weak and strong acids and bases all make good materials to check. When barium hydroxide solution is titrated with sulfuric acid, barium sulfate precipatates, and the lightbulb dims and then goes out.
Using a large container of ice water, a can of Pepsi (or Coke) sinks while a can of Diet Pepsi (or Diet Coke).
28. Boyle's Law
An apparatus for the overhead projector includes a viewable pressure gauge attached to a large syringe; allows investigation of the relationship between pressure and volume.
This demonstration, generally used in the organic chemistry courses, associates shapes of molecules with odors.
Two solutions mix together to produce a fluorescent yellow glow that can be seen when the room lights are off. Potassium ferricyanide crystals added to the mixture increase the intensity.
31. Carbon Snake
In this demonstration, concentrated sulfuric acid is mixed with sucrose, producing a column of carbon which grows out of the beaker.
32. Ice Bomb
Demonstrates the expansion of the water when it freeze; a cast-iron ice bomb is filled with ice water, closed, then placed in an ethanol/dry ice bath, which is then covered. Expansion of the water ruptures the bomb and causes several pieces of shrapnel to hit the cover.
33. Nassau Reaction
This 'Halloween Demo' occurs when equal amounts of three solutions are added together. The solution turns bright orange, then suddenly turns dark blue. (Or pour half of the third solution into the mixture and wait till a nice orange color develops before adding the remainder of that solution.) Large flask with Jack-o-lantern face is available for Halloween lectures.
Heating silica and magnesium powder together produces silane; putting the silane compound in weak hydrochloric acid causes small fires
The solubility of lead iodide is about 10 times greater in hot water than in room temperature water. Dissolving lead iodide in boiling water and then letting it cool down slowly (or fast by using ice) causes the golden lead iodide crystals to form and float down to the bottom of the flask.
A tall graduated cylinder of green-blue copper chloride solution and a strip of aluminum react to produce changes in colors and temperature, with the formation of a solid.
Using a ferric nitrate solution, this demo illustrates how pH affects solubility. A precipitate forms when ammonium hydroxide is added to the test tube (when the pH reaches ~10). Then the prcipitate redissolves when hydrochloric acid is added (pH < 6).
38. Reichardt's Dye
This demo shows the dramatic affect that solvent polarity can have on absorption wavelength. In a relatively non-polar solvent such as acetone, Reichardt's dye is green; as the solvent is made more polar by the addition of water, it becomes blue, purple, magenta, red and finally orange. This can be shown quite clearly on an overhead projector.
39. Gas Creation
This demo shows how combining a liquid (dilute hydrochloric acid) and a solid (calcium carbonate) can generate a gas; a rubber stopper is placed on the test tube, and the tube is shaken to combine the liquid and powder. The resultant carbon dioxide gas causes the rubber stopper to fly about 10 feet.
40. Tyndall Effect
Using a flat-sided fish bowl and a flashlight, the effects of turbidity are shown. When only water is in the bowl, a beam of light will be virtually invisible where it passes through the bowl, and bright white where it emerges. When a thiosulfate solution is added, the turbidity increases, and the beam will be visible where it passes through the mixture. That beam will appear blue, while the light emerging from the bowl appears orange.
This demo shows the differing colors of copper. A solution is taken from the light blue of copper sulfate, to dark blue of Cu(II)(NH3)5 complex ion, to a colorless solution of copper(I), to finally precipitating out the reddish copper metal.
A super-saturated solution of sodium acetate is made and cooled overnight. Once cooled, a tiny amount of sodium acetate is added to the solution. The entire solution then crystalizes within a few seconds.
A mixture of potassium chlorate and sucrose is placed on a watchglass with a drop of sulfuric acid. This causes a reaction which starts slowly, but then bursts into flames, and creates lots of smoke.
Chlorine gas is generated by a combination of bleach and hydrochloric acid. This gas then reacts with sodium metal causing it to burn with a bright yellow flame.
Barium hydroxide and ammonium chloride are mixed in an Erlenmeyer flask. A small wet wooden block placed on the flask will freeze to the flask.
46. Iodine Clock
Two solutions are mixed together and in a few seconds the solution turns from pale yellow to dark blue. Varying the amounts of the solutions gives diffferent times before the change occurs.
Sealed plastic petri dishes with varying numbers of BBs inside are used to demonstrate many of the microscopic differences among gases, liquids, and solids.
An ordinary cotton towel is immersed in a solution of alcohol and water and lighted over a burner. A blue flame surrounds the towel as the alcohol burns without burning the towel.
A lecture-sized temperature meter is used to show the exothermic reaction of adding lithium chloride to a beaker of water.
A film of nylon is formed at the interface between two immiscible liquids. When the film is lifted from the container, it is continually replaced forming a hollow thread of polymer.
Copper sulfate is heated on a crucible turning from the origianal blue color to white. Squirting water on the dehyrated copper sulfate turns the copper sulfate back to blue.