Rates of Yellow

rates of yellow
Written by: Casey Rogers (ChemDemo) on June 18, 2013.

A reaction between two white solids occurs when lead nitrate and potassium iodide are shaken forcefully producing a mixture of yellow and white solid products. The reaction occurs almost instantaneously when aqueous solutions of these compounds are mixed, precipitating yellow lead iodide.

Pb(NO3)2 + 2KI → PbI2 + 2KNO3

Igniting Magnesium

burning magnesium
Written by: Casey Rogers (ChemDemo) on May 8, 2013.

When magnesium is ignited, it is readily oxidized by oxygen in the air producing an incredibly bright light and intense heat.
2Mg (s) + O2 (g) → 2MgO (s)

Fake Blood

Written by: Casey Rogers (ChemDemo) on June 23, 2011.

This demonstration makes iron (III) thiocyanate complexes that are deep red in color, resembling fake blood.

Colorless to White

silver nitrate with potassium chloride
Written by: Casey Rogers (ChemDemo) on June 22, 2011.

This demonstration makes a white precipitate by mixing equal amounts of silver nitrate and potassium chloride.
AgNO3 (aq) + KCl (aq) → KNO3 (aq) + AgCl (s)

Red Sunset

Written by: Casey Rogers (ChemDemo) on June 14, 2011.

The reaction of sodium thiosulfate and hydrochloric acid produces colloidal sulfur which clouds the solution. As the sulfur concentration increases, shorter wavelengths are scattered and longer ones pass through, this causes an increase of reddish color to appear on the overhead.
Na2S2O3 + HCl → 2NaCl + SO2 + S + H2O

Red Cabbage Indicator

red cabbage indicator in common household solutions
Written by: Casey Rogers (ChemDemo) on June 14, 2011.

Anthocyanin, which is found in red cabbage, is a natural indicator that can be easily extracted.

Colorful Oxidation States

Written by: Casey Rogers (ChemDemo) on June 14, 2011.

This demo has a solution in a flask that changes color from pink to blue to green to yellow to orange as the solution is stirred. The different colors are due to the different oxidation states of Mn.

Gummy Bear Sacrifice

gummy bear in potassium perchlorate
Written by: Casey Rogers (ChemDemo) on June 14, 2011.

Potassium chlorate is such a strong oxidizer that when a gummy bear, which is mostly sugar, is placed into it, the sugar is oxidized violently producing noise and a flame. This demo can be used to discuss strong oxidizers as well as how much energy is in sugar.

Genie in a Bottle

decomposition of hydrogen peroxide
Written by: Casey Rogers (ChemDemo) on June 14, 2011.

This demo makes use of the catalytic decomposition of hydrogen peroxide to produce a column of steam out of a flask, that looks like a genie coming out of a bottle.
2H2O2 → 2H2O + O2, KI is a catalyst

Elephant’s Toothpaste

decomposition of hydrogen peroxide elephant's toothpaste old foamy
Written by: Casey Rogers (ChemDemo) on June 13, 2011.

Hydrogen peroxide is decomposed quickly in liquid soap with the help of a catalyst to create a large volume of foam that grows out of a graduated cylinder. The soap bubbles contain oxygen.
2H2O2 → 2H2O + O2, KI is a catalyst

Electrocute a Pickle

pickle electrocution
Written by: Casey Rogers (ChemDemo) on June 13, 2011.

When electricity is passed through a pickle, it is conducted through Na+ and the Cl- ions that are present in the pickle. The electricity excites the electrons to a higher energy state, and when the fall back to ground state they emit a yellow/orange light.

Dry Ice in Universal Indicator

dry ice universal indicator acid base reaction
Written by: Casey Rogers (ChemDemo) on June 13, 2011.

Universal indicator goes from red (pH 4) to violet (pH10) as the pH of a substance changes. Adding NaOH to water starts the solution off at pH 8-9 (blue). When dry ice is added to water it forms carbonic acid, and lowers the pH, which is the reason for the color changes. The “fog” that we see is condensed water vapor though, not carbon dioxide gas.

Disappearing Ink

Written by: Casey Rogers (ChemDemo) on June 13, 2011.

This demo uses acid base chemistry and an indicator to make an ink that will appear or disappear depending on the solution added to it. Phenolphthalein, which is clear, reacts with a base, and then turns pink.

Decomposition of Ammonium Dichromate

ammonium dichromate on fire, decomposition
Written by: Casey Rogers (ChemDemo) on June 13, 2011.

This demo decomposes ammonium dichromate using a fuse soaked in ethanol. The reaction is a violent one, that resembles a volcano. Ammonium dichromate is an orange solid, while chromium (III) oxide is a dark green solid.
(NH4)2Cr2O7(s) → Cr2O3(s) + N2(g) + 4H2O(g)

Colored Flames

manganese strontium sodium copper potassium salts burning in ethanol
Written by: Casey Rogers (ChemDemo) on June 9, 2011.

When different ionic compounds are heated, electrons around the metal atom become excited and jump energy levels. When the electrons fall back to ground state they release light and heat energy. The amount of energy released determined the wavelength and color of the light released, resulting in different colored flames.

Blue Bottle Demo

methylene blue equilibrium under basic conditions
Written by: Casey Rogers (ChemDemo) on June 8, 2011.

Under basic conditions glucose is oxidized while methylene blue is reduced, changing from blue to colorless. The reduction reaction can be reversed by shaking the flask which forces oxygen into solution, which oxidizes the methylene blue, thus turning it back to blue. If the flask is let sit, the oxygen will come out of solution making the solution colorless and ready to shake again.

Black Foam

Written by: Casey Rogers (ChemDemo) on June 8, 2011.

When sugar is reacted with concentrated sulfuric acid it creates a black foam made of elemental carbon. The water that is produced in the reaction is gaseous and causes the foam to rise.
H2SO4 + C12H22O11 → 12C + 11H2O + a mixture of acid and water