Hello Professors!

Today is Thursday, February 1st, 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  

-Reactions in aqueous solutions 

-Thermochemistry 

  

Suggested Demonstrations 

 

Potassium and Water – Drop a piece of potassium into an aquarium containing water and phenolphthalein to produce H2 (g) and KOH (aq) – the heat of reaction ignites the H2 (g) and a lavender flame is observed (from the K+), while the indicator turns pink from the formation of KOH. 

 

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. 

 

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 

-Precipitation reactions 

  

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.  

Effect of Temperature on NO2 ↔ N2O4 Equilibrium – Immerse sealed tubes of NO2/N2O4 in hot and cold water to show how temperature shifts the equilibrium position and to show the reversibility of the shift; red-brown NO2 predominates at high temperatures and colorless N2O4 at lower temperatures  

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.  

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. 

 

Amphoteric Hydroxides: Al3+ and Fe3+ – add NaOH to samples of Al(NO3)3 and Fe(NO3)3 to form insoluble metal hydroxides, then add HNO3 and more NaOH to different samples of each to identify which metal hydroxides are amphoteric 

  

General Chemistry for Engineers:  

  

Weekly topics  

-Gases 

-The Periodic Table and Atomic Structure 

  

Suggested Demonstrations (please electrocute the pickle) 

 

Squashing Pop Cans with Atmospheric Pressure – use atmospheric pressure to squash pop cans.  

Boiling Water at Room Temperature – Show water boiling at room temperature in a beaker in an evacuated bell jar, then put your hand in the water after boiling to convince students of its low temperature. (Upon request, we can give you a clean beaker and tap water if you want to drink the boiled water)  

Graham’s Law – Allow concentrated NH3 and concentrated HCl to vaporize and meet in a horizontal glass tube, forming a ring of NH4.  

 

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. 

 

Elementary Chemistry:  

  

Weekly topics  

-Organic Compounds 

  

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. 

  

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