Hello Professors!
Today is Thursday, February 15th (happy belated Valentines Day!), and these are the hottest and trendiest demonstrations for the upcoming week!
The chemicals are absolutely flying off the shelves, so order while you can!
Here is the link (Password: hydrogen) to order as well as the full list of demos; as always, early orders are very appreciated!
General Chemistry I:
Weekly topics
-Chemistry Electronic Structure of Atoms
Suggested Demonstrations
Gas Discharge Tubes of the Noble Gases – show that different gases give different colors when subjected to an electric discharge (H2 tube also available)
Atomic Spectra: Flame Tests – Introduce various metal salts (e.g. NaCl, SrCl2, CuCl2) into an open flame to produce brilliant colors associated with exciting metal cations.
Pickle Electrocutor – Run an electric current through a dill pickle using a special apparatus to show students that the brine in the pickle conducts electricity, and the current heats and excites the sodium atoms present to a higher energy level. The emission of photons as the sodium returns to the ground state accounts for the yellow color of the light.
General Chemistry II:
Weekly topics
-Acid/base equilibria
-Electrochemistry
Suggested Demonstrations
Le Chatelier’s Principle: Iron (III) Thiocyanate Equilibria – Apply stress to the Fe3+ + SCN- → FeSCN2+ system in five different ways to show the equilibrium shifts accompanying changes in the concentration of reactants.
Acidic and Basic Oxides – Dissolve several oxides (CaO, ZnO, CO2, P4O10) in water containing universal indicator to show a range of basic and acidic oxides
Yamada and Dry Ice – Add a chunk of dry ice to a 2 L cylinder containing a basic solution and Yamada universal indicator; the dry ice gradually acidifies the solution causing the color to change in the order purple, blue, green, yellow, orange.
Concentration Cell – Set up a concentration cell with 1 M Cu 2+ on the bottom and
0.01 M Cu 2+ on the top with copper plates immersed in the solutions as electrodes; the
voltage read from a multimeter should be close to 59 mV as predicted by the Nernst equation
Electrolysis of Water – Electrolyze water (dilute Na2SO4 solution with indicator) in the Hoffman apparatus to decompose it into its component elements, hydrogen and oxygen. If desired, you can test the H2 (g) and/or O2 (g) produced with a flame and a glowing splint, respectively.
General Chemistry for Engineers:
Weekly topics
-Chemical Bonding and Molecular Structure
-Molecules and Materials
Suggested Demonstrations
Models: Contrast models of NH2—NH2, NH=NH, and N≡N to show the decreasing N–N bond length as the bond order increases
Polarity and Geometry – Show the dependence of dipole-dipole forces on geometry by contrasting the effect of a charged rod on streams of H2O and “CCl4” (actually hexane) flowing from burets
Paramagnetic O2 – Demonstrate the paramagnetism of liquid oxygen by pouring first N2(ℓ), then O2(ℓ) between the poles of a powerful magnet on the overhead projector or document camera.
Nylon 6-10 – Demonstrate the polymerization of hexamethylenediamine with sebacoyl
chloride to produce the polyamide Nylon 6-10.
Covalent Network Solids – show large models of different arrangements of pure carbon: graphite,
diamond, and/or C60 (buckminsterfullerene).
Crystalline and Amorphous Solids – contrast a piece of charcoal, a large quartz crystal, a piece of pumice, and a polished quartz crystal (SiO 2).
We’ve also got all the crystal structures of metals and materials, there are just too many to put here.
Elementary Chemistry:
Weekly topics
-Chemical Reactions
-Carbohydrates
Suggested Demonstrations
Oxidation of Alcohols – Demonstrate the oxidation of ethanol with K2Cr2O7 on the overhead projector; the alcohol solution changes from orange to green to blue as the Cr(VI) is reduced; this reaction is the basis for the Breathalyzer test.
Ammonium Dichromate Volcano – Ignite a pile of (NH4)2Cr2O7 volcano in an aquarium to produce N2 (g), H2O (g), and Cr2O3 (s). The resulting reaction looks very much like an erupting volcano.
Combustion of Candy– Contrast the rate of oxidation of sucrose in the body (by eating
some candy) with the oxidation of sucrose by KClO 3 (as shown by dropping some candy
into molten KClO 3, producing steam and a lavender flame. Body temperature is ~37C,
and the melting point of KClO 3 is 368C.
Disaccharides – Display a large plastic Darling model of sucrose
Black Carbon Snake – add concentrated H2SO 4 to sugar in a tall beaker to produce a
black “snake” of carbon that grows out the top of the beaker.
Foundations of General Chemistry:
Weekly topics
-Solutions and aqueous reactions
Suggested Demonstrations
Crystallization of Supersaturated Sodium Acetate Solution – Add a tiny crystal of sodium acetate to a 2 L flask of a super-saturated solution to cause the solid to crystallize out, leaving almost no liquid – this demonstration is beautiful and dramatic, as well as being quite exothermic. Alternatively, you can pour the solution slowly over a single crystal to build up a column of solid sodium acetate
Yamada and Dry Ice – Add a chunk of dry ice to a 2 L cylinder containing a basic solution and Yamada universal indicator; the dry ice gradually acidifies the solution causing the color to change in the order purple, blue, green, yellow, orange
Electrolysis of Water – Electrolyze water (dilute Na2SO4 solution with indicator) in the Hoffman apparatus to decompose it into its component elements, hydrogen and oxygen. If desired, you can test the H2 (g) and/or O2 (g) produced with a flame and a glowing splint, respectively.
The Tyndall Effect – Demonstrate the Tyndall effect and simulate a sunset on the overhead projector by reacting Na2S2O3 with HCl to produce a colloidal suspension of sulfur.
Thank you and have a great week!
-The Demo Lab
PS if you are ahead/behind of schedule let us know so we can adjust the demos accordingly. Currently we are simply using the syllabi to guess where your respective classes are at. and here is the link again 🙂: Demo Ordering Link
Kind regards,
Lynda Reynolds