This is a hands on activity that demonstrates how chemical reactions change the properties of a substance. In this case, borax (sodium borate) changes the sticky properties of Elmer’s glue, to make a fun to play with putty. Elmer’s glue is polyvinyl acetate, and when sodium borate is added to it, a cross-linked polymer is created giving the glue very different properties that make for a fun activity for students!
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
Anthocyanin, which is found in red cabbage, is a natural indicator that can be easily extracted.
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.
When the bill is dipped in the water/alcohol mixture then lit on fire, the water protects the bill from burning. A large amount of the alcohol is vaporized from the heat causing a large flame around the bill.
C2H5OH + 3O2 → 2CO2 + 3H2O
This demo shows how a precipitation reaction works. The precipitate formed is a common ingredient in chalk.
CaCl2 (aq) + Na2CO3 (aq) → NaCl (aq) + CaCO3 (s)
When basic baking soda (NaHCO3) is combined with acidic lemon juice (mainly citric acid, H3C6H5O7) an acid base reaction occurs. The reaction releases CO2 which can be captured using dish soap to form bubbles.
H3C6H5O7 (aq) + 3 NaHCO3 (s) → 3 CO2 (g) + 3 H2O (l) + Na3C6H5O7 (aq)
This demo uses a stove made out of aluminum cans that can be lit using knowledge of vapor pressure. When the acetone surrounding the stove is lit, the acetone in the stove boils, releasing vapors that are then lit on fire.
CH3OCH3 + 3O2 → 2CO2 + 3H2O
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.
This demo uses sodium hydroxide to plate Zn on the surface of a copper penny, making it appear silver in color. Zinc is oxidized in sodium hydroxide. The remaining electroplating process is not fully understood. The silvery penny can be heated to melt the zinc and copper together, creating a gold colored alloy.