Teacher Notes
|
||||||||
---|---|---|---|---|---|---|---|---|
Santa in a SnowstormDemonstration Kit![]() IntroductionCreate a giant “snowflake crystal” scene in a jar while learning about solubility principles. This lab had a serendipitous beginning when a solution of benzoic acid was forgotten on a lab bench and allowed to cool! Voila! “Snow”! Concepts
MaterialsTap water
Benzoic acid, 20 g* Beaker, 2-L Bottle, plastic, 3-L* Holiday plastic figurine* Hot glue gun Hot plate Stirring rod Tape, electrical *Materials included in kit. Safety PrecautionsBenzoic acid is moderately toxic by ingestion. Avoid contact with skin, eyes, clothing and respiratory tract as it is a severe irritant. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Use exhaust ventilation to keep airborne concentrations low. Keep the bottle capped to avoid breathing the vapors. DisposalPlease consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. The benzoic acid solution should be neutralized, then flushed down the drain with excess water according to Flinn Suggested Disposal Method #24a. Procedure
Student Worksheet PDFTeacher Tips
Correlation to Next Generation Science Standards (NGSS)†Science & Engineering PracticesConstructing explanations and designing solutionsDisciplinary Core IdeasMS-PS1.A: Structure and Properties of MatterHS-PS1.A: Structure and Properties of Matter Crosscutting ConceptsStability and changePerformance ExpectationsMS-PS1-2: Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred. Answers to Questions
DiscussionA solution is formed by dissolving a solute such as benzoic acid in a solvent such as water. The process of a solid solute dissolving in a solvent is a surface phenomenon. Dissolving is a surface phenomenon because it is those molecules or ions at the surface of the solid, not those in the interior, or bulk, of the solid, that interact with and dissolve in the surrounding solvent. As the surface ions dissolve, the next layer of ions now becomes the surface layer. This new surface layer interacts with the ions already in solution. This interaction at the surface of a crystal continues until the crystal is completely dissolved, or until the solution can accept no more solute. A solution is said to be unsaturated when it contains a lower concentration of solute than it can at a given temperature and pressure. A saturated solution contains as much solute as it can at a given temperature and pressure. When the temperature is increased, the solubility usually increases and more solute will dissolve. If this solution is then cooled, the “extra” solute that dissolved with heat will once again precipitate. This is the chemical phenomenon occurring when the benzoic acid precipitates out as “snow” in this demonstration. ReferencesSpecial thanks to Richard Chapleau, Lancaster High School, Lancaster, CA, for providing Flinn Scientific with this idea. Recommended Products
|
||||||||