How to Demonstrate a Supersaturated Solution





Introduction: How to Demonstrate a Supersaturated Solution

This demonstration illustrates three concepts: the process of crystal growth from a solution, the properties of saturated solutions, and the idea that a seed crystal must be made of the same substance as the crystals that will grow.


Saturated water solution of sodium acetate
Small samples of crystals of sodium chloride, sugar, or other substances
Overhead projector
Two or three petri dishes for use on the overhead projector stage
Paper towels for spillage


After explaining the concepts of saturation, supersaturation, crystallization, and seed crystals, pour the supersaturated solution into a petri dish on the overhead projector stage to a depth of no more than 1/4". Add one or more seed crystals of sodium acetate trihydrate to the saturated solution. Needle shaped crystals will start to grow slowly. The process will continue for 20-30 minutes. Plan on discussing other material while this is happening; come back to the overhead projector to check the progress of the crystallization every few minutes and comment on the process of crystal growth.

To illustrate the fact that the seed crystal must be made of the same material as the crystals to be formed, repeat the process of pouring more saturated solution into one or two other petri dishes on the overhead projector stage. Add a crystal of sodium chloride to one dish. Nothing happens. Repeat with a sugar crystal. Again, nothing happens. If you wish, repeat with some other substance. Nothing happens. Now add a crystal of sodium acetate trihydrate and cyrstallization will commence.


Sodium acetate trihydrate is unusual in the stability of its supersaturated solutions. Most such solutions will spontaneously crystallize from the slightest mechanical disturbance. This should be pointed out to your class in the overall discussion.

Supersaturated solutions of sodium acetate trihydrate are extremely sensitive to the presence of even microscopic crystals of the substance. It is not unusual to have solutions spontaneously crystallize in a place where sodium acetate trihydrate has been previously handled. Before repeating this demonstration it is good practice to wipe down all surfaces with a moist sponge to dissolve any microcrystals of sodium acetate trihydrate that may be lurking in the vicinity. Wash your hands between shows.


Sodium acetate trihydrate and its solutions in water are neither toxic nor harmful.


B. Shakhashiri, Chemical Demonstrations, 1, 27.



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    My daughter wants to use this experiment along with growing borax and sugar crystals for a science fair. She must have an experiment that can be graphed. Can you think of a good science fair hypothesis & graph for this? I was thinking of does the chemical makeup of the solution effect the time it takes for crystals to form...create all 3 types of crystals, & graph time it takes to form crystals. What do you think?

    The sodium acetate demo is one of a supercooled stuff, not supersaturated. Supersaturated is when you actually have a solution (solute + solvent).
    Think about it like this, its been raining and snowing a lot in Nevada (you, adding the solute) and all that water runs into lake Mead (the solution) and it has way too much water for the Hoover dam (the solvent) to hold back, so it has to let out some of that water (crystals forming in solution) to bring the lake back down to normal levels (going from supersaturated to typical saturation).
    That's supersaturation. This Mountain Dew demo, much like the sodium acetate demo, is supercooling.

    dude this damn video doesn't even lo- ALL HAIL THE HYPNOTOAD. pickles the frog pickles the frog pickles the frog pickles the frog pickles the frog pickles the frog pickles the frog pickles the frog pickles the frog pickles the frog pickles the frog pickles the frog pickles the frog

    also not just sodium acetate any super saturated soultion should be handled this way .

    nope but it's not so easy to clean if you have pure sodium aceta just make sure you reheat it ,pour it out,risne and wash with water.Also use some sort of cleaner .Treat as any other type of cleaning .

    Why does this video not play ?

    How do you have access to so much stuff?

    you can make NaC2H3O2 with baking soda and vinegar.

    how do you make sodium acetate with baking soda and vinegar