Author: Troy Kovick, Mary Harris
Source: Amended from an idea by Joan Hall
Students will compare the absorbency of regular disposable diapers with Swimmers in fresh water and salt water.
What should students know as a result of this lesson?
What should the students be able to do as a result of this lesson?
Show the students what sodium polyacrylamide or soil moist looks like. Explain that this is a superabsorber polymer. In other words, it likes to absorb water. How much water will it absorb? Each of you will be given one gram of the crystals and you will have to decide how much water it will absorb in 24 hours. Encourage the class to have a range of water amounts to 1ml to 500 ml. Have the students set up the experiment and label each container. The next day, have the students look at all the containers to determine which one absorbed the most water. Students may drain off any excess water by holding their hand over the opening to contain the crystals as they drain into another container and measure this amount. Ask the students to determine what was the percent absorption of water. (This should be about 250 %)
In this opening activity use questioning and teachers' observations to assess the students understanding of scientific processes: hypothesizing, conducting a fair test, collecting data, reporting findings, and analyzing data, as well as their comprehension of the science concepts behind the activity. Ask the students where the water went. The polymer is hydrophilic which means it likes water.
Give each student group a diaper for a 25# child. Ask them to find the mass in pounds on the nursery scale (this will be about .1 pounds.) Have the students place the diaper in a sink filled with water for 10 minutes. Carefully lift the sopping diaper out of the sink and let drain a little. Find its mass in pounds. Record all data on white board or notebook. Repeat process with Swimmer. Have the students determine the amount of water absorption of each diaper by subtracting the initial mass from the final mass. (The swimmers should hold the same amount of fresh and salt water and the regular diapers should hold twice the amount of fresh water as salt water.) Check to see if all the data is recorded.
Students share their findings with the class and report their findings.
During a class discussion, ask these questions:
Students could also conduct searches for more information about superabsorber polymers on the Internet.
Check for understanding based on responses to questions.
Distribute another disposable diaper and Swimmer to each group along with an ample supply of salt water. The salt water simulates ocean water that is 3.5% salt or 3.5 g of table salt in 96.5 ml of water. Large buckets are helpful to hold the salt water.
The students should repeat the exploration activity using the salt water in place of the fresh water. The students should graph this information from the exploration activity and this activity and draw their conclusions. Discuss their graphs and help with conclusions. Regular diapers absorb salt water but with only about one half of the total water absorbed compared to fresh water. Swimmers behave the same in salt water as they do in fresh water. Swimmers do not contain any superabsorber polymer.
In this elaboration activity use questioning and teachers' observations to assess the students understanding of scientific processes: hypothesizing, conducting a fair test, collecting data, reporting findings, and analyzing data, as well as their comprehension of the science concepts behind the activity.
Direct Instruction: Helping with the class discussions.
Cooperative Learning: Throughout activity.
Others: The extension of this activity is to put the large swollen soil moist crystals (from the engagement activity) in salt water and see if they will lose volume as the salt pulls the water out of the polymer. If you start with about 450 mL of swollen crystals and add salt water to the container, the crystals will decrease in volume to about 200 mL in 24 hours.
Misconceptions: Students may believe that Swimmer diapers absorb as well as regular diapers, but they merely function to collect solid waste.
Common Core Standards:
The contents of the regular diapers could become airborne and cause respiratory issues. Enforce existing safety rules for conducting lab activities in the science class.
Most students will go on to have children and will use diapers of these designs.
Grouping Suggestions 2-4 per group.
Pacing/Suggested Time: Begin the activity at the end of a period and resume the following day. Lesson could take two class periods to complete.