Hello Professors!
Today is Thursday, February 8th, 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
-Thermochemistry
Suggested Demonstrations
Hot and Cold Packs – Combine NH4NO3 (s) and water in a Ziploc bag to make an instant “cold pack”.
Thermite – Perform the thermite reaction, in which Al and Fe2O3 react to produce molten iron.
NOTE: 48 hour notice is required for this demonstration
Combustion of Ethanol Vapors – Allow a small amount of ethanol to vaporize in a large carboy, pour out the excess liquid, and hold a lighted splint to the mouth of the container – the impressive reaction also demonstrates the explosive flammability of organic vapors.
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.
General Chemistry II:
Weekly topics
-Acid/base equilibria
-Redox Reactions
-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.
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
-The Periodic Table and Atomic Structure
-Chemical Bonding and Molecular Structure
Suggested Demonstrations (please electrocute the pickle)
Gas Discharge Tubes of the Noble Gases – show that different gases give different colors when subjected to an electric discharge (H2 tube also available)
Fireworks Balloons – Show the brilliant colors of metal cations in a fun way by igniting hydrogen balloons containing metal salts.
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.
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.
Elementary Chemistry:
Weekly topics
-Organic Compounds
-Chemical Reactions
Suggested Demonstrations
Disappearing Styrofoam Cup – Make a Styrofoam (expanded polystyrene) cup disappear by placing it in a dish of acetone.
Miscibility and Immiscibility – Mix ethanol and colored water in one beaker and hexane and colored water in another to demonstrate miscibility and immiscibility due to differences in the intermolecular forces of alcohols as the size of the alkyl group increases.
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.
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