Instant Crystals Lab from Flinn Scientific

4. Cover the na~k \vith Parafilnl or vvith a 1OO-n1L beaker. Allovv' the solution to cool to rOOln teInperature undisturbed or. tospeed up the cooling process. run cool water over the sides of the flask 111aking sure no tap water gets into and contaminatesthe solution. The flask can no\v sit undisturbed until you are ready for the presentation. Take care not to disturb thesolution as even slight 1110ven1ent may cause crystallization to occur before you're ready.ProcedureTips1. While holding a single sodiul11 acetate trihydrate crystal over the open nlouth of the flask. snap your fingers and allow thecrystal to drop into the flask. You might want to say SOlne 1l1agic \vords like "abracadabra presto" as you snap your fingers.The single crystal should start a chain reaction of crystallization.2. Immediately turn the flask upside down as crystallization occurs. The crystallized sodium acetate \vill not fall out.3. Feel the sides of the flask. The flask will be \varm since this is an exothermic process.4. The solution may be used over again by reheating it to redissolve the sodiuln acetate.• Use caution if substituting a non-Pryex' hydron1eter cylinder for the flask in this den10. The tenlperature differential n1aycrack the cylinder. Use a Pyrex cylinder instead or allow the supersaturated solution to coo] slightly before pouring it intothe cylinder.• The addition of too 111uch water will result in leftover liquid after recrystallization.• This den10nstration can be perfonl1ed for a larger audience by using 640 g sodiu111 acetate trihydrate and 120 mL water.• Topics of discussion may include saturated solutions. supersaturated solutions. crystallization. and exothennic processes.• Uses for supersaturated sodium acetate solutions include hot packs and hand wanners.lJVariations of this demonstration include perfornling the crystallization in a SOO-rnL graduated cylinder or placing a singlecrystal in a shallow container and pouring the solution onto the crystal. A buret may also be used to release the solutiononto the crystal. These two variations can produce fairly tall columns of the recrystallizing sodium acetate.• Use a Flinn CheInCam"l or other video nlicroscopy unit to provide a close-up view of the crystallization process.DiscussionA supersaturated solution of sodium acetate trihydrate (the clear solution) will recrystallize by the addition of a single crystalof the solid. A supersaturated solution is a solution which contains a greater an10unt of dissolved substance than is present in asaturated solution at the same temperature. A saturated solution is a solution which contains the Inaximu111 amount of a dissolvedsubstance at a given tenlperature.A supersaturated solution can be n1ade by gradually cooling a saturated solution without agitation so that crystals do notfonn. Supersaturated sol utions are extremely unstable and will precipitate, or crystallize. upon addition of just one crystal of thesolute. Even slight shaking or agitation Inay be enough to cause crystallization to begin.DisposalThe sodium acetate solution may be re-used or flushed down the drain with excess water. Please consult a current FlinnScientzfic Catalog/Reference Manual for proper disposal procedures.Materials for Instant Crystals-Supersaturated Solution are available from Flinn Scientific, Inc.Catalog No. Description1Price/EachS0036 Sodium acetate, 100 9 I Consult YourCurrent FlinnS0037 Sodium acetate, 500 9Catalog/ReferenceGP3050 Erlenmeyer Flask, 500-mL I Manual.-2­CD 2003 Flinn Scientific, Inc. All Rights Re~er\'ed.IN700