{"id":66,"date":"2024-10-24T15:04:05","date_gmt":"2024-10-24T19:04:05","guid":{"rendered":"https:\/\/sites.temple.edu\/chemdemo\/?p=66"},"modified":"2024-10-25T16:22:13","modified_gmt":"2024-10-25T20:22:13","slug":"osmosis-colligative-properties","status":"publish","type":"post","link":"https:\/\/sites.temple.edu\/chemdemo\/2024\/10\/24\/osmosis-colligative-properties\/","title":{"rendered":"Osmosis &amp; Colligative Properties"},"content":{"rendered":"\n<h2 class=\"wp-block-heading\">Overview<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Sodium Polyacrylate<\/strong> is used to demonstrate an osmosis-like effect, specifically in the context of diapers.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">Purpose<\/h2>\n\n\n\n<p>To illustrate the flow of water attempts to even out concentration gradients.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Procedure<\/h2>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Introduction<\/strong>:<\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Hold up a diaper and discuss its function.<\/li>\n\n\n\n<li>Reveal that it contains sodium polyacrylate.<\/li>\n<\/ul>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Experiment Setup<\/strong>:<\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Use approximately 2 g of sodium polyacrylate with 50 mL of deionized (DI) water, then add another 50 mL of DI water.<\/li>\n\n\n\n<li>Repeat with a fresh 2 g of sodium polyacrylate and a saturated salt solution.<\/li>\n\n\n\n<li>Draw the structure of sodium polyacrylate for students to see, highlighting that sodium is trapped in the \u201ccells.\u201d<\/li>\n<\/ul>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Demonstration<\/strong>:<\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Take a few scoops of sodium polyacrylate into the bottom of a beaker and add water. Control the ratio to create a gel within seconds, allowing the beaker to be turned upside down.<\/li>\n\n\n\n<li>Ask students why sodium polyacrylate absorbed the water.<\/li>\n\n\n\n<li>Show an illustration of the swollen sodium polyacrylate.<\/li>\n\n\n\n<li>Discuss how to extract the water by adding salt, which alters the concentration gradient.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Key Concepts<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Hydrogels<\/strong>: Cross-linked polymers with hydrophilic groups, such as carboxylic acid groups, which are water-attracting.<\/li>\n\n\n\n<li><strong>Chemical Structure<\/strong>:<\/li>\n\n\n\n<li>Sodium polyacrylate, also known as poly(sodium propenoate), is a long, randomly coiled polymer.<\/li>\n\n\n\n<li>Removal of Na+ causes negative charges on oxide ions along the polymer chain to repel, leading to uncoiling. Water molecules are attracted to these charges via hydrogen bonding.<\/li>\n\n\n\n<li>Sodium polyacrylate can absorb over five hundred times its weight in pure water, but less in salty water.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">Diapers and Leakage<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Diapers may leak due to pressure forcing water out of the polymer beads. Manufacturers increase cross-link density to mitigate this.<\/li>\n\n\n\n<li>The presence of salts in urine complicates absorption. Sodium polyacrylate can&#8217;t absorb all the water when salt concentration is balanced both inside and outside the polymer.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">Osmotic Pressure Experiment<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Use a thistle tube with a membrane in a 2 L graduated cylinder next to the cabinet.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Additional Experiment<\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Dialysis Tubing<\/strong>:<\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Fill one bag with 25% glucose and 2% starch; place it in a beaker with deionized water and KI\/I2 solution.<\/li>\n\n\n\n<li>Fill another bag with deionized water and iodine; place it in a beaker with a saturated salt solution and about 5 mL of starch solution.<\/li>\n\n\n\n<li>Observe the flow of water and the iodine\/starch complex formation.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">Chemical Data Table<\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Compound<\/th><th>Mass (g)<\/th><th>Chemical Formula<\/th><th>Freezes at (\u00b0C)<\/th><th>Kf (\u00b0C\/m)<\/th><\/tr><\/thead><tbody><tr><td>Acetic acid<\/td><td>25.0<\/td><td>C2H4O2<\/td><td>16.6<\/td><td>3.90<\/td><\/tr><tr><td>Benzoic acid<\/td><td>2.44<\/td><td>C7H6O2<\/td><td>(to be determined)<\/td><td>(to be determined)<\/td><\/tr><tr><td>Benzene<\/td><td>&#8211;<\/td><td>&#8211;<\/td><td>5.5<\/td><td>5.12<\/td><\/tr><tr><td>Camphor<\/td><td>&#8211;<\/td><td>&#8211;<\/td><td>179.8<\/td><td>39.7<\/td><\/tr><tr><td>Carbon disulfide<\/td><td>&#8211;<\/td><td>&#8211;<\/td><td>\u2212112<\/td><td>3.8<\/td><\/tr><tr><td>Carbon tetrachloride<\/td><td>&#8211;<\/td><td>&#8211;<\/td><td>\u221223<\/td><td>30<\/td><\/tr><tr><td>Chloroform<\/td><td>&#8211;<\/td><td>&#8211;<\/td><td>\u221263.5<\/td><td>4.68<\/td><\/tr><tr><td>Cyclohexane<\/td><td>&#8211;<\/td><td>&#8211;<\/td><td>6.4<\/td><td>20.2<\/td><\/tr><tr><td>Ethanol<\/td><td>&#8211;<\/td><td>&#8211;<\/td><td>\u2212114.6<\/td><td>1.99<\/td><\/tr><tr><td>Ethyl ether<\/td><td>&#8211;<\/td><td>&#8211;<\/td><td>\u2212116.2<\/td><td>1.79<\/td><\/tr><tr><td>Naphthalene<\/td><td>&#8211;<\/td><td>&#8211;<\/td><td>80.2<\/td><td>6.9<\/td><\/tr><tr><td>Phenol<\/td><td>&#8211;<\/td><td>&#8211;<\/td><td>41<\/td><td>7.27<\/td><\/tr><tr><td>Water<\/td><td>&#8211;<\/td><td>&#8211;<\/td><td>0<\/td><td>1.86<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\">References<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Website for Images<\/strong>: <a href=\"http:\/\/www.tutornext.com\/help\/sucrose-osmosis\">TutorNext<\/a> (may be subject to copyright).<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>Overview Purpose To illustrate the flow of water attempts to even out concentration gradients. Procedure Key Concepts Diapers and Leakage Osmotic Pressure Experiment Additional Experiment&#8230;<\/p>\n<div class=\"more-link-wrapper\"><a class=\"more-link\" href=\"https:\/\/sites.temple.edu\/chemdemo\/2024\/10\/24\/osmosis-colligative-properties\/\">Continue Reading<span class=\"screen-reader-text\">Osmosis &amp; Colligative Properties<\/span><\/a><\/div>\n","protected":false},"author":36673,"featured_media":0,"comment_status":"open","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[],"class_list":["post-66","post","type-post","status-publish","format-standard","hentry","category-demonstrations","entry"],"_links":{"self":[{"href":"https:\/\/sites.temple.edu\/chemdemo\/wp-json\/wp\/v2\/posts\/66","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/sites.temple.edu\/chemdemo\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/sites.temple.edu\/chemdemo\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/sites.temple.edu\/chemdemo\/wp-json\/wp\/v2\/users\/36673"}],"replies":[{"embeddable":true,"href":"https:\/\/sites.temple.edu\/chemdemo\/wp-json\/wp\/v2\/comments?post=66"}],"version-history":[{"count":1,"href":"https:\/\/sites.temple.edu\/chemdemo\/wp-json\/wp\/v2\/posts\/66\/revisions"}],"predecessor-version":[{"id":67,"href":"https:\/\/sites.temple.edu\/chemdemo\/wp-json\/wp\/v2\/posts\/66\/revisions\/67"}],"wp:attachment":[{"href":"https:\/\/sites.temple.edu\/chemdemo\/wp-json\/wp\/v2\/media?parent=66"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/sites.temple.edu\/chemdemo\/wp-json\/wp\/v2\/categories?post=66"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/sites.temple.edu\/chemdemo\/wp-json\/wp\/v2\/tags?post=66"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}