Science Project – Grades III, IV, V,
& VI
Lesson Plan for Inquiry – The Use of Polymers
in Diapers
Rationale:
In addition to its use in disposable diapers, sodium polyacrylate has many other uses. It is one of the few fields of study where school age children are actually able to engage in scientific inquiry and will be able to make genuine contributions to science. This super absorbent polymer and other such polymers are widely used in applications such as forestry, gardening, and landscaping as a means of conserving water.
This inquiry lesson will give the children an opportunity to examine the advantages and disadvantages of using these polymers in various fields. For example, the super absorbent polymer is able to reduce the amount of time that is spent watering a lawn, a garden, or even a house plant by 50 to 80 percent! While students may consider water-absorbing polymers to be a modern convenience, they will also foresee the impact that such technology is having on parts of the world that are plagued by drought.
The students will also investigate some of the concerns about using disposable diapers. The concerns have been about the dyes, sodium polyacrylate (the super absorbent gel), and dioxin (which is a by-product of bleaching paper) that are used to manufacture disposable diapers. While disposable diapers have the ability to hold large quantities of urine, there tends to be a slight wetness against the baby’s skin, which can lead to rashes. Sodium polyacrylate has also been linked in the past to toxic shock syndrome, allergic reactions and is very harmful and potentially lethal to pets. Other concerns about disposable diapers include the cost and environmental harm it can cause to the earth.
Goals:
Children are naturally curious. To encourage this curiosity and foster learning, certain types of mental and physical skills are needed, which are skills for acquiring useful information that has practical value and carries real meaning for learners, meaning that is constructed from the learners’ experiences. The children, by engaging in the inquiry process of this lesson will develop positive attitudes towards science, use their curiosity to construct new ways of investigating and understanding, and acquire knowledge for practical learning and everyday living. This is the fundamental premise of constructivism and is addressed in this lesson by encouraging the children to predict, examine, extend, and evaluate (steps of the learning cycle) through a hands-on approach.
Instructional Objectives:
Cognitive:
Affective:
Psychomotor:
SOL:
3.1 The student will plan and conduct investigations in which
a) predictions and observations are made;
b) objects with similar characteristics are classified
into at least two sets and two subsets;
c) questions are developed to formulate hypotheses;
d) volume is measured to the nearest milliliter and
liter;
e) length is measured to the nearest centimeter;
f) mass is measured to the nearest gram;
g) data are gathered, charted, and graphed (line plot,
picture graph, and bar graph);
h) temperature is measured to the nearest degree Celsius;
i)
time is measured
to the nearest minute;
j)
inferences are
made and conclusions are drawn; and
k) natural
events are sequenced chronologically.
3.3 The student will investigate and understand that objects are
made of materials that can be described by their physical properties. Key
concepts include
a) objects are made of one or more materials;
b) materials are composed of parts that are too small to
be seen without magnification; and
c) physical properties remain the same as the material is
reduced in size.
4.1 The student will plan and conduct investigations in which
a) distinctions are made among observations, conclusions,
inferences, and predictions;
b) hypotheses are formulated based on cause-and-effect
relationships;
c) variables that must be held constant in an
experimental situation are defined;
d) appropriate instruments are selected to measure linear
distance, volume, mass, and temperature;
e) appropriate metric measures are used to collect,
record, and report data;
f) data are displayed using bar and basic line graphs;
g) numerical data that are contradictory or unusual in
experimental results are recognized; and
h) predictions are made based on data from picture
graphs, bar graphs, and basic line graphs.
5.1 The student will plan and conduct investigations in which
a) rocks, minerals, and organisms are identified using a
classification key;
b) estimations of length, mass, and volume are made;
c) appropriate instruments are selected and used for
making quantitative observations of length, mass, volume, and elapsed time;
d) accurate measurements are made using basic tools (thermometer,
meter stick, balance, graduated cylinder);
e) data are collected, recorded, and reported using the
appropriate graphical representation (graphs, charts, diagrams);
f) predictions are made using patterns, and simple
graphical data are extrapolated;
g) manipulated and responding variables are identified;
and
h) an understanding of the nature of science is developed
and reinforced.
6.1 The student will plan and conduct investigations in which
a) observations are made involving fine discrimination
between similar objects and organisms;
b) a classification system is developed based on multiple
attributes;
c) precise and approximate measurements are recorded;
d) scale models are used to estimate distance, volume,
and quantity;
e) hypotheses are stated in ways that identify the
independent (manipulated) and dependent (responding) variables;
f) a method is devised to test the validity of
predictions and inferences;
g) one variable is manipulated over time, using many
repeated trials;
h) data are collected, recorded, analyzed, and reported
using appropriate metric measurements;
i)
data are
organized and communicated through graphical representation (graphs, charts,
and diagrams);
j)
models are
designed to explain a sequence; and
k) an understanding of the nature of science is developed
and reinforced.
Materials Required:
Diapers (one per child)
Gallon-sized zip-lock bags (with zippers)
Gloves (non-latex) – child size
Droppers
Colored liquid – preferably 2 colors to choose from
Disposable cups (clear)
Safety goggles
Frog dissecting aprons
Scissors
Magnifying glasses
Teaspoons or plastic spoons
Salt
Paper towels and wipes
Polymer tri-fold display
K-W-L sheets
Pencils
*Several examples of polymers, both hydrophobic and hydrophilic
Procedure:
(Exploration – 5-7 minutes)
Allow students to examine the examples provided. This can be accomplished at the table or sitting as a group on the floor.
“These items all contain polymers.
You may or may not know what a polymer is. Take a few moments and discuss these
items as a group, then place them into 2 sets. Each item must fit into
one of the two sets.”
Have the students, working as a group, discuss the items’ similarities and differences, and then have them place the items into 2 different sets according to a similar property or properties.
“Let’s take a look at your 2 sets
of items and examine how you separated them. What is your reasoning for placing
these items into this set? What about the items in the second set?”
Some students may not agree with the reasoning or placement of items. Allow them an opportunity to discuss their grouping strategies. Time may not allow for every student to actually rearrange the items according to their individual reasoning.
(Explanation – 5-7 minutes)
At this point, discuss what a polymer is.
“After looking at these items, how
can we begin to describe a polymer? What do you think a polymer does?”
Eventually, the discussion should involve water, and the students should be introduced to the terms “hydrophobic” and “hydrophilic.” Find out if the students already know what these terms mean.
“Let’s look at our items again and,
this time around, let’s think about these items in relation to water. How might
we begin to separate these items?”
Allow discussion. Have the students separate the items according to water absorption – do they repel (hydrophobic) or absorb (hydrophilic) water?
“Today we are going to take a
closer look at the hydrophilic polymer, sodium polyacrylate. This polymer is
found in diapers. But before we examine this polymer, let’s take our K-W-L
sheet and write down what we already know about polymers in the K-section of
the sheet.”
Some students may not have used K-W-L sheets before – take a moment and discuss the importance of these learning tools.
“Now that we know a little bit
about polymers, what would you want
to know about the polymer found in the baby diaper? You will put this
information in the W-section of your sheet.”
Begin the experiment.
(Expansion – 15-20 minutes)
(CAUTION:
The powder found in the diaper (sodium polyacrylate) will irritate the nasal
membranes if inhaled. Avoid eye contact. If it gets into the eyes, they
will become dry and irritated. Be sure to wash hands after use.)
Have students put on safety goggles and non-latex gloves, to protect eyes
and skin. “Why do you think the goggles and gloves are
necessary?”
Use a pair of scissors to cut off the paper or plastic edge around the entire diaper. Place the padded, middle part of the diaper into the zip-closing plastic bag.
Reach into the bag with both hands and separate the cotton, paper, and
plastic layers of the diaper. “What would be a
reason for leaving the diaper in the bag as you separate it into its layers?” Leave
all material in the bag. Seal the bag, and shake it for about 1
minute. Look at the bottom of the bag as you tilt it to one side. The
students should notice white granules collecting in the corner of the bag. “Stop and look at your bag. What do you observe happening
inside the bag?”
Now, without opening the bag, move the cotton, plastic, or other large pieces of material toward the top of the bag. Keep the material up there as you shake the bag again. This will allow the granules to fall down to the bottom without getting picked up by the cotton.
After you have about one teaspoon of granules in the corner of the bag, slowly open the bag and remove the large pieces of material. Throw them away. Now, carefully pour the granules into a small cup. Fill another plastic cup about half full with colored water – the students may choose which color to use.
Using a dropper, add one drop of the colored water to the granules. Continue
adding one drop at a time to the granules and observe. “What
do the granules appear to be doing?”
“Predict what might happen if you
begin to add larger amounts of water, such as a teaspoon.” Have students
increase the amount of colored water added. “What
is happening? What do you observe? How does your observation compare with your
prediction?”
**If time permits, have students experiment with salt. “What do you think will happen to the polymers when salt is added? Why?” Have students begin adding small amounts of salt to the polymer. The polymers should actually begin to release the water.
(Evaluation – 1-2 minutes)
Have students complete the L-section of their sheet with what they have learned about the hydrophilic polymer, sodium polyacrylate.
Assessment:
The students will discuss what they have learned about polymers, and more specifically, about the hydrophilic polymer, sodium polyacrylate.
What is a polymer?
How are polymers similar? How are they different?
What are the properties of sodium polyacrylate?
How does it hold so much moisture?
Critical thinking:
What are some of its applications in the real world?
What are some of the disadvantages of using it?