Diaper+Polymer

Shannon Fusina __ snf5024@psu.edu __ Sean Haggerty __ swh5085@psu.edu __
 * Diaper Polymer **

This lesson is intended for students at a middle school level (grades 6-8). The lesson will be regarding polymers and their properties; specifically sodium polyacrylate which is found in disposable diapers.

This lesson covers Pennsylvania state standards: 3.2.7C, identify and use the elements of scientific inquiry to solve problems 3.4.7A, describe concepts about the structure and properties of matter 3.7.7B, use appropriate instruments and apparatus to study materials 3.8.7B, explain how human ingenuity and technological resources satisfy specific human needs and improve the quality of life
 * Standards Covered **

The student will be able to explain how why a diaper is able to absorb liquid. The student will be able to define "super absorbent polymer." The student will be able to give examples of how polymers are used in everyday life.
 * Lesson Objectives **

The polymer used in diapers is sodium polyacrylate. This polymer belongs to a family of polymers known as hydrophilic, or water attracting, polymers. It has the unique ability to absorb up to 800 times its mass. The water is initially drawn into the polymer by osmosis since the concentration outside the polymer is much higher than inside the coiled chains. The two chains responsible for the absorption potential are the carbonyl and sodium, which create the polymer chain (this will not be explained in as much detail). In the presence of water, the sodium dissociates from the carbonyl creating ions. The like forces repel each other creating a "swelling" effect in which the water is absorbed into the polymer preventing it from leaving. The many cross-links between each polymer chain prevent infinite swelling, which leads to a finite amount each molecule can absorb. Along with being found in diapers, sodium polyacrylate, along with other super-absorbent polymers, have many uses including soil to retain water, by florists to store dirt-free water, in filtration units used by airplanes and automobiles, and in Grow-Creature toys.
 * <span style="font-family: 'Times New Roman',serif;">Content Explanation **


 * <span style="font-family: 'Times New Roman',serif;">Materials: **
 * <span style="font-family: 'Times New Roman',serif;">1 pack disposable diapers
 * <span style="font-family: 'Times New Roman',serif;">Scissors
 * <span style="font-family: 'Times New Roman',serif;">2 large beakers to store crystals and cotton material
 * <span style="font-family: 'Times New Roman',serif;">Water
 * <span style="font-family: 'Times New Roman',serif;">Graduated cylinder


 * <span style="font-family: 'Times New Roman',serif;">Body of the Lesson (POE Lesson, use chapter 3 from your Probing Understanding text as a guide): **

<span style="font-family: 'Times New Roman',serif;">a) **<span style="font-family: 'Times New Roman',serif;">Predict **<span style="font-family: 'Times New Roman',serif;">(approximate time frame): 5 Minutes- The students will be asked what they know about baby diapers, if they have any younger siblings that used diapers when they were a baby, and if they have ever torn one open to see what is inside. The students will initially be shown a beaker filled with water, a beaker containing the polymers from a baby diaper, and a beaker containing some of the cotton fabric from a baby diaper. The students will then be asked what part of the diaper will absorb the water the best, the cotton or the pellets (polymer).

<span style="font-family: 'Times New Roman',serif;">b) **<span style="font-family: 'Times New Roman',serif;">Observe **<span style="font-family: 'Times New Roman',serif;"> (approximate time frame): 2 minutes- The demonstration will be performed by adding half of the water to each of the other two beakers. Each beaker will be given a couple of seconds to equilibrate and then the students will be asked what they observe in each beaker. When they notice that the water seemed to have been absorbed in the non-cotton beaker, the beaker can be held over the instructor's head, and the students can predict if the any water will fall onto the instructor's head if it is flipped over. Other than students eating the polymer, there are no safety concerns. The visual and physical characteristics will be discussed during the demonstration. No assistant will be needed.

<span style="font-family: 'Times New Roman',serif;">c) **<span style="font-family: 'Times New Roman',serif;">Explain **<span style="font-family: 'Times New Roman',serif;"> (approximate time frame): 3 minutes- This is a good opportunity to talk about why they are used in diapers. The word polymer will be described in detail. The story about astronauts needing an absorbing polymer to clean up liquids in space will be an interesting fact that will give some scope for the usefulness of these materials. The amount that the polymers can absorb will not be discussed in this section. The polymer will be explained by calling it hydrophilic (water loving) and saying that water gets trapped inside of the polymer due to parts of its structure (this will not be heavily stressed so a large explanation will not be needed).

<span style="font-family: 'Times New Roman',serif;">d) **<span style="font-family: 'Times New Roman',serif;">Predict **<span style="font-family: 'Times New Roman',serif;">(approximate time frame): 4 minutes - The students will be given diapers and plastic bags and told to rip open the diaper and obtain the polymer by shaking the contents of the diaper around in the plastic bag. The students will be given different sized beakers and asked what they think will happen if they add water (corresponding to the size of the beaker) to the polymer that they obtained.

<span style="font-family: 'Times New Roman',serif;">e) **<span style="font-family: 'Times New Roman',serif;">Observe **<span style="font-family: 'Times New Roman',serif;"> (approximate time frame): 1 minute - The students will add the water to the beaker with the polymer and observe what happens. The only safety concern is to make sure students do not eat the polymer. No assistant is needed.

<span style="font-family: 'Times New Roman',serif;">f) **<span style="font-family: 'Times New Roman',serif;">Explain **<span style="font-family: 'Times New Roman',serif;"> (approximate time frame): 4 minutes - It will be explained that the polymer can absorb between 300 and 800 times its weight in water depending on the type of water. This will then be used to describe what the students see in their beaker. If there was leftover water, they had more than the 300x weight of the polymer in water. If there was no remaining water they were under that amount.