Solubilit y of Packing Peanut s:

Transcription

1 Solubilit y of Packing Peanut s: Lab Activity Developed by: Mary Agnes Baum, Teacher (maryagnes_baum@hermitage.k12.pa.us) Table of Contents Overview... 1 Science St andards Addressed... 1 Goals/ Object iv es... 2 Mat erials and Equipment... 2 Key Vocabulary Words... 2 Saf et y... 2 Procedure ( t ot al est imat ed t ime- 1 hr)... 2 Assessment Examples... 3 Locat ing Mat erials... 5 Background Inf ormat ion... 5 Ref erences... 6 Acknowledgement... 6 Overview This lesson explores t he concept of a solute and solvent. Starch and St yrofoam packing peanut s are dissolved in wat er and acet one t o demonstrate polar and non-polar solutes and solvents. Students first est imat e, t hen measure, t he number of packing peanuts that will dissolve in 50 ml of solvent. Science St andards Addressed U.2 Evidence, models, and explanations A.1 Abilities necessary to do scientific inquiry B.1 Propert ies and changes of propert ies in mat t er E.2 Underst andings about science and t echnology 1/6

2 Goals/ Object ives Students will classify polymers as nat ural or synt het ic. Students will define and ident ify t he solvent and solut e in a solut ion. St udent s will dist inguish bet ween a polar and a non-polar molecule. Mat erials and Equipment St arch packing peanut s St yrofoam ( polyst yrene) packing peanut s Acetone 100mL beakers St irring rods Saf et y goggles Key Vocabulary Words Polymer- A class of natural or man made substances made from smaller unit s called monomers arranged in long chains. Solubilit y- Amount or ability of one material to dissolve in another. Polar Molecule- A type of molecule that will dissolve in water. Non- polar Molecule- A type of molecule that will dissolve in non-polar subst ances. Solut e- The substance that get dissolved. - A substance that dissolves another Substance. s are often liquids. Safet y Safety goggles are required for this activity. Students should be careful not to get acetone on their hands or directly inhale acetone vapor. Be aware that acetone is flammable and will dissolve ink. Procedure ( total estimated time- 1 hr) Set -Up (5 minut es) 2/6

3 Make sure each lab group has two 100 ml beakers and two stirring rods. Have a large supply of St yrof oam and St arch packing peanut s ready. During (45 minutes) Part 1 : Obt ain t wo packing peanut s labeled A (st arch) and t wo labeled B (polystyrene) from the instructor. Write down at least three different properties for each type of packing peanut. Fill a 100 ml beaker with 50 ml of water and a second 100 ml beaker with 20 ml of acetone. Prepare a dat a t able, labeling one column peanut t ype, one column wat er and one column acet one. Beneat h t he peanut t ype column, writ e A and B on separate rows. Under the water column, write dissolves or does not dissolve. Repeat for the acetone column. Add one packing peanut labeled A to the beaker of water. Record in the data table eit her dissolves or does not dissolve. Next, add t he second packing peanut labeled A into the beaker of acetone. Record observation as dissolves or does not dissolve. Repeat procedure with packing peanuts labeled B. Answer quest ions under Part 1. Part 2 : Est imat e how many A packing peanut s will dissolve in 5 0 ml of wat er and how many B packing peanuts will dissolve in 20 ml of acetone. Then add t he A packing peanut s one at a t ime t o t he wat er t o determine the actual number that will dissolve. Record the actual value. Repeat t he procedure wit h t he B packing peanut s and t he acet one. Record t he act ual v alue. Answer the Part 2 quest ions: Tear-Down (5 Minutes) Gat her all used lab equipment. Used poly st y rene can be recy cled. Assessment Examples Part 1 : 1. Why did packing peanut A dissolve in wat er but not in t he acet one? 3/6

4 (Packing Peanut A is a polar material and will not dissolve in acet one a non-polar solvent. A will however dissolve in water, a polar solvent.) 2. Why did packing peanut B dissolve in t he acet one but not in t he water? (Packing Peanut B is a non-polar material and will not dissolve in water a polar solvent. B will however dissolve in acet one, a nonpolar solvent.) 3. What is a solvent? (A solvent is the thing, often a liquid, which dissolves something else.) 4. What is a solut e? (A solute is the thing, sometimes a solid, which gets dissolved). 5. Ident if y t he solvent s and solut es f or each set of condit ions. (The packing peanuts are solutes, acetone and water are the solvent s.) 6. What is t he difference bet ween a polar and a non-polar molecule? (A polar substance will dissolve in polar solvents, like wat er. A nonpolar substance will dissolve in non-polar solvents like acetone, or gasoline). 7. Which packing peanut is a nat ural polymer and which is a synt het ic polymer? (Packing Peanut A is the natural polymer starch. Packing Peanut B is the synthet ic polymer polyst yrene.) Part 2 : 1. How did t he act ual number of packing peanut s compare t o your est imat ed value? (Answers will vary, but many students will underestimate the number packing peanut s which will dissolve in 20 ml of acet one.) 4/6

5 2. Were you surprised by t he act ual number of packing peanut s t hat dissolved? Explain. (Some students will be surprised, others will not. Most of the volume in a packing peanut is taken up by air. This makes it seem like t here is more mat erial in each packing peanut, and therefore it looks like few will dissolve. The solubilit y of bot h t he solut es in their respective solute is also high.) 3. Why it would not be a good idea t o t ransport gasoline in a polystyrene cont ainer? (Gasoline, being a non-polar solvent, would likely dissolve the polystyrene container.) Locat ing Mat erials Packing peanut s can be f ound in shipping boxes and at shipping out let s. Acetone can be found at the hardware store in the paint section. Background Inf ormat ion St yrofoam packing peanut s are made from blow molded polystyrene. The name St yrofoam is pat ent ed by t he Dow Chemical Corporat ion and was discovered in 1941 by Ray McIntire. Polystyrene is identified in other products by resin identification code (recycle code) six. It is used in CD cases, some food containers and disposable petri dishes. Although blow molded polystyrene is less dense than water, solid polystyrene has a density of about 1.05 g/ cm 3 and will sink in water. The st arch packing peanut s are a nat ural mat erial usually made from corn st arch. The use of st arch based packing peanut s st art ed in t he 1990 s. St arch packing peanut s are biodegradable and non-toxic. They are safe when accidentally consumed by people or pets, but they are not tasty. St arch packing peanut s will dissolve fast er in hot wat er t han cold wat er. The st arch molecules are polar and cont ain hydroxyl (-OH) groups. These OH groups hydrogen bond wit h wat er molecules and as a result t he 5/6

6 st arch dissolves in wat er. Polyst yrene has no hydroxyl groups and is nonpolar. Therefore polystyrene will not dissolve in water. Ref erences Polymer Ambassadors ht t p:/ / American Extrusion International / Perry A. Cook, Sue Hall, and Jill Donahue Pondering Packing Peanut Polymers Journal of Chemical Educat ion Vol 80 No p1288b Acknowledgement This module was developed by t he ASM Foundat ion K-12 committee's Middle School Task Force wit h input f rom t eachers and st af f and edit ing assist ance from Pet er Kazarinoff, all of whose contributions are acknowledged wit h t hanks. Copyright ASM International 2010; Permission is granted for free use by instructors for educational purposes. 6/6