Gak Polymers. Grade Level: 8 th

Transcription

1 Gak Plymers Grade Level: 8 th This is a micr lessn designed t last ne 30 minute class perid (with an additinal 15 minutes fr English t Chinese translatin and questins frm the audience). Science/Mathematics Cncepts and Cnceptual Understanding: Mnmers are mlecules able t bnd in lng chains Plymers are made up f many mnmers linked tgether Miscnceptins students may have: Students may have truble grasping that mnmers and plymers are bth chains f mlecules, but represent different levels f cmplexity. They may als have truble grasping that the crsslinkers themselves are mlecules. Science and Mathematics Prcess/Inquiry Skills: Gak (r silly putty) is an example f a plymer made frm hydrcarbns jined tgether by weak intermlecular bnds. Elmer s glue is the surce f hydrcarbns, and sdium brate links mnmers tgether t frm the plymer. Students will create gak while experimenting with what rati f Elmer s glue t sdium brate will prduce the greatest bunce (height rebunded after drpping frm a cnsistent height). List f Materials: 55% Elmer s glue slutin in water 4% brax slutin (sdium brate) Cups Ziplck bags Optinal fd clring Safety Precautins: Students shuld wear gggles and ptentially lab aprns, as brax is a bleaching agent and culd burn the eyes. Instructinal Objectives Students will be able t: Create gak using their wn rati f Elmer s glue t brax slutin Cllect data n hw high the gak bunces Make cnclusins frm class data as t what rati f elmer s glue t brax prduces the best bunce

2 Understand that brax is respnsible fr crss linking mlecules in Elmer s glue tgether t frm plymers Engage Phase: Begin by shwing students images r physical examples f structures made ut f plymers (plastics, plants, DNA). Explain that all matter is cmpsed f atms, and that tw r mre atms can make up a mlecule. Lng chains f mlecules (r mnmers) can be crss linked tgether t frm plymers. Questins fr students: What are all f these structures (images r physical examples) cmpsed f? What is all matter in the wrld cmpsed f? When atms bnd tgether, what d they frm? Hw are atms bnded t frm mlecules? Hw are mlecules bnded t ther mlecules? Acetate grups in Elmer s glue crss linking with B OH grups in brax mlecules t frm plymers. Explre Phase: Student grups f 4 will be given the attached prcedure (belw) and access t the materials listed abve. Students will recrd the amunt f Elmer s glue and brax slutin they use in their gak, as well as the height the ball f gak bunces when drpped frm 50 centimeters. Explain Phase:

3 Students recrd their recipe fr gak and height bunced by their gak ball n the blackbard. Instructrs will ask students t identify which grups gak was the mst successful buncer. Elabrate Phase: The attached wrksheet will allw students t think abut plymerizatin in tw different ways, making the cnnectin between the chemical structure n the page and the experiment they just cmpleted. Evaluate Phase: (include rubric) Students will explain n their wrksheet why they believe that the crrect rati between Elmer s glue and brax actually matters, which will allw us t evaluate whether they understand hw the tw slutins are interacting (plymerizing) t frm gak.

4 Gak Plymer Prcedure 1) Wear gggles and lab aprns. 2) Decide hw much Elmer s glue t use in yur gak (n mre than 50 ml). Measure and pur this amunt int yur cup. 3) Decide hw much f the Brax slutin t add t each cup (n mre than 30 ml). Measure and pur this amunt int yur cup. 4) Immediately stir the slutins tgether using the wden stick. 5) After a cuple f minutes f mixing, the silly putty can be remved frm the cup and kneaded with yur hands. Knead until the desired cnsistency is reached. 6) Using a ruler t measure, drp the ball frm a height f 50 centimeters. T what height des it rebund?

5 Student Wrksheet Elmer s Glue Mlecule Brax Mlecule Describe what is happening in the abve image. Hw des this relate t the experiment yu cnducted tday?