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Undergraduate Chemistry
Chemistry Demonstrations
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Chemistry comes to life in Penn State classrooms!

At PSU, many of our chemistry courses features live, in-class demonstrations that are specially designed to enrich each student's educational experience. The demonstrations are designed by a dedicated team of professionals, who work hard to ensure that every chemistry student can see science in action! 

 

Demos

 

 

Rate of Catalysis Demonstration

Video Credit: Philip Stemple and Bob Hummer

This demonstration shows that a catalyst speeds up the rate of a reaction. Hydrogen peroxide oxidizes sodium thiosulfate to sulfuric acid according to the reaction below. 

Na2S2O3(aq) + 4 H2O2 (aq)     Na2SO4(aq) + H2SO4(aq) + 3 H2O(l)

Starting from an alkaline solution, the resulting pH change can be followed using Universal Indicator, which changes from purple (basic) to blue, then green, then yellow (acidic). The solution labeled “non-catalyst” on the left shows this color change, while the control solution on the far right contains only a basic solution of the indicator.  Sodium acetate is also present to buffer the solution. Adding an ammonium molybdate catalyst speeds up the color change, as shown in the center solution labeled “catalyst”.

Glowstick Catalysis Demonstration

Video Credit: Philip Stemple and Bob Hummer

This demonstration shows that a catalyst speeds up the rate of a reaction. The overall light-emitting reaction in a glowstick is the oxidation of phenyl oxalate esters by hydrogen peroxide to generate phenol derivatives and carbon dioxide.  A glowstick consists of a flexible plastic casing with a central cavity.  A glass vial in the cavity contains the oxalate and a fluorescent dye, while the cavity around the vial contains the peroxide.  When the plastic outer casing is bent, the inner glass ampule breaks, the reactants mix, and the following reaction begins:

image-20200424111223-1

An intermediate is formed during this reaction, which collides with a fluorescent dye molecule and transfers energy to create an excited state.  The dye molecule then returns to its electronic ground state, releasing energy in the process.  Most of the energy is released as light, but there is also some heat.  The emission of light from molecules by way of chemical excitation is called chemiluminescence. When sodium salicylate is added, it acts as a basic catalyst to speed up the reaction and make the glow brighter.

Superconductor Demonstration

Video Credit: Philip Stemple and Bob Hummer

This demonstration shows that a superconductor can levitate an object above it when cooled.  Superconductors are a special class of materials that show no resistance to the flow of electricity. Such materials exhibit superconducting behavior when cooled below what is called the superconducting transition temperature, Tc. This demonstration illustrates what happens when the superconductor YBa2Cu3O7 (abbreviated YBCO) is cooled below its transition temperature of 92 K with liquid N2 (which has a boiling point of 77 K).  The black disc in the video is the superconductor, and when a cube of magnetic neodymium is placed above the cooled superconductor it levitates above the disc.  This is called the Meissner effect, and is due to the expulsion of a magnetic field from the superconductor during its transition to the superconducting state. The magnet can be made to spin as it hovers in the air.

Liquid Oxygen

Video Credit: Philip Stemple and Bob Hummer

This demonstration shows that dioxygen is magnetic and is attracted to the poles of a magnet.  An aluminum foil funnel is suspended above a magnet and filled with liquid nitrogen.  Since the boiling point of N2 (77 K) is lower than that of O2 (90 K), blue liquid oxygen condenses out of the air on the outside of the foil funnel and drips down into the magnet. It sticks briefly to the poles before it warms up and boils away.