Hello Professors! 

Today is Monday, January 29th, 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

-Chemical Reactions and Stoichiometry

-Reactions in aqueous solutions

 

Suggested Demonstrations

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.

 

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.

General Chemistry II:

 

Weekly topics

-Chemical equilibria

-Acid/base equilibria

 

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.

 

General Chemistry for Engineers:

 

Weekly topics

-Stoichiometry

-Gases

 

Suggested Demonstrations

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.

Avogadro’s Law – Three flasks containing equal amounts of acetic acid are fitted with balloons containing different amounts of NaHCO3; mix the reagents by lifting and shaking the balloons: the balloons will inflate with CO2 to a volume proportional to the number of moles produced, in accordance with Avogadro’s law.

H2/O2 Balloon Series – Light a series of balloons containing different ratios of H2 (g) and O2 (g): pure H2, 2:1, 1:1, 1:2, pure O2. The loudest bang occurs when the ratio is stoichiometric, 2:1.

 

 

Elementary Chemistry:

 

Weekly topics

-Compounds- how elements combine

 

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)

Halogens – Display flasks containing the halogens chlorine, bromine, and iodine.

The VSEPR model – Use 5 sets of balloons to illustrate the VSEPR shapes: linear, trigonal planar, tetrahedral, trigonal bipyramidal, and octahedral.

 

 

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