Sam

=//Experimenting with Supersaturated Solutions//=


 * __Abstract:__**

Sodium Acetate is a commonly found example of a supersaturated solution. It can be created by mixing Sodium Bicarbonate (Baking Soda) with Acetic Acid (White Vinegar). This reaction can be explained using this equation:

CH3COOH + NaHCO3 = CH3COO- + Na+ + H2O + CO2 Acetic Acid + Sodium Bicarbonate = Acetate + Sodium + Water + Carbon Dioxide.

The minus sign behind the Acetate indicates that the acetate a negatively charged ion. Normally, the negatively charged ions won't remain in the solution. However, the negatively charged ions are offset by the positively charged sodium ions, keeping both of them in the mixture. The water formed will also remain in the mixture, but the Carbon Dioxide will not as it is a gas.


 * __Hypothesis:__**

Since the Acetate and the Sodium only remain in the mixture because of the negatively and positively charged ions, they will solidify the minute they leave the mixture.


 * __Materials:__**

Acetic Acid (100 grams of Distilled 5% White Vinegar) Sodium Bicarbonate (7 grams of Baking Soda)

Stirring these two compounds together in a beaker and evaporating the left over water forms Sodium Acetate




 * __Experimenting with the Sodium Acetat__****__e:__**

Pouring the Sodium Acetate into a pan will cause the solution to solidify immediately after it touches the pan. The Sodium Acetate will solidify to itself, so you can make different shapes with it.

Another experiment to try: Try dissolving the Sodium Acetate in near boiling water. Continue to stir the Sodium Acetate into the water until no more can be dissolved. Pour the mixture into a glass container, and leave it in the freezer. After it has cooled, remove the mixture and pour it into a glass tray. The second you touch the mixture, it will completely solidify into solid ice.

__**Procedure**__

1) Take about 200 mL of water, and heat it to about 80 degrees Celsius (not boiling, but until the point where bubbles start to form) 2) After the water starts to simmer, add in the Sodium Acetate (I used nearly 250 grams of Sodium Acetate) 3) Continue stirring the Sodium Acetate into the water until no more Sodium Acetate will dissolve in the water. It doesn't matter how much water or sodium acetate you use, it just matters whether or not the water is completely saturated with sodium acetate, and any remaining sodium acetate starts to appear at the bottom. 4) Leave the Sodium Acetate in the freezer until the temperature reaches room temperature or lower. Leaving the Sodium Acetate in the freezer for too long will cause the Sodium Acetate to completely freeze. I left the Sodium Acetate for about half an hour before taking it out. 5) Pour the Sodium Acetate you want to freeze in a completely sterile container (no dust should be in the container). 6) Touch the Sodium Acetate will create a nucleation center in the middle of the liquid, and the liquid will immediately turn into a solid block of ice, with a temperature of nearly 53 degrees Celsius. Eventually, the solidified Sodium Acetate will cool down, but will remain a solid.




 * __Observations__**


 * After touching the Sodium Acetate, it crystallizes outwards from the nucleation point.
 * Although the crystallized Sodium Acetate Trihydrate looks sort of like ice, it's a lot slushier and more opaque than regular ice from water.
 * After crystallization, the temperature of the Sodium Acetate reaches well over 50 degrees Celsius. This would mean that the crystallization is part of an exothermic reaction.
 * Anything can act as a nucleation center, so if the beaker isn't clean enough the Sodium Acetate will immediately crystallize.

__**Hypothesis - Why this Experiment Works**__

The liquid you form by adding Sodium Acetate with water is Sodium Acetate Trihydrate: a sodium acetate molecule combined with three water molecules. This chemical compound is written as: NaC2H3O2 + 3H2O.

Sodium Acetate Trihydrate can be easily supercooled. Even though it has a freezing point of 54 degrees Celsius, Sodium Acetate can easily be cooled to reach temperatures much lower than room temperature. Once you touch the liquid, you create a nucleation center that forces several liquid molecules into solid molecules, causing the molecules around it to also solidify. During this reaction, the temperature of the Sodium Acetate Trihydrate can reach over 50 degrees Celsius.