SCIENCE FAIR PROJECT

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Once we have the supersaturated solution cooled slowly pour the solution on some crystallized solid acetate. acetate towers whose size increases as progressing crystallization are obtained.

Once critalizado sodium acetate, we can return to repeat the experiment taking advantage of these same crystals. Only we have to be heated to about 100 ° until it forms a solution again and again cool in the refrigerator as before.

What happen?

Crystallization is a process by which one goes from a relatively disordered system (liquid) to a much neater system (glass). According to the second law of thermodynamics, the transition from a disordered to an ordered system energy system down to offset this increase in order to be produced. The solubility of a solid in a liquid depends on temperature.

A supersaturated solution is a solution in which there are more solid allowed at this temperature (metastable thermodynamic equilibrium). The saturated hot solution becomes a supersaturated solution cold.

This phenomenon can be seen in supersaturation solutions sodium acetate trihydrate in water. When dissolved in water at high temperature, when cooled ions and sodium acetate orientate spontaneously fail so that the crystal lattice, so a metastable thermodynamic equilibrium solution is obtained is not formed. The supersaturated solution may crystallize spontaneously depositing a seed crystal of sodium acetate. This spontaneous crystallization occurs with the latent heat release resulting in an increase in system temperature.

Why some supersaturated solutions fail to crystallize at room temperature is a difficult fact to explain. Fahrenheit discovered that a liquid can remain unfrozen below its freezing point. Fahrenheit eliminated the air dissolved in water and then put the water in bottles closed, exposing them to cold air. It thus discovered that water could remain liquid at temperatures below its freezing point. But when the containers were agitated instant freezing occurred.

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