1. Lab Session 11
How can we characterize the “absorption” capacity of a superabsorbent polymer?

2. Your Challenge
Imagine that you work for a company that is interested in using superabsorbent polymers, in particular sodium polyacrylate, as ion and molecule “scavengers” for removal of toxic substances dissolved in water.
Your task is to design a set of experimental procedures to characterize the capacity of the polymer to absorb a variety of dissolved substances.

3. Your Tasks
In order to accomplish your goals, you have to complete three basic tasks:
Task 1: Determine how the water absorption capacity of sodium polyacrylate varies as a function of sodium chloride concentration.
Task 2: Quantify the mass of copper (in Cu form dissolved in water) that sodium polyacrylate can absorb per gram of this polymer as a function of time.
Task 3: Pose a research question to investigate in the lab, and design and implement and experiment to answer it.
Weak electrolyte

4. Task 1: Your Plans
Task 1: Determine how the water absorption capacity of sodium polyacrylate varies as a function of sodium chloride concentration.
In your groups, share your ideas about how to solve this problem, and come up with a common plan that your group will implement.
Once you have a plan, share it with your lab instructor and the rest of the class.
mL solution/g polymer
EXPECTED OUTCOME
NaCL (g/L)
x x2 10

5. Your First Challenge
Determine how the water absorption capacity of sodium polyacrylate varies as a function of sodium chloride concentration.
Available resources:
1.0 g of polymer (0.25 g per test);
10.0 g/L NaCl solution;
Filter papers;
Plastic stirring rod;
Volumetric glassware;
Digital scale.
You have 45 minutes

6. Claims, Evidence, and Reflection
Present your claims and evidence to the class. Decide as a group which data should be shared to facilitate the analysis.
Collectively analyze the data and discuss what they tell you about the absorption properties of the polymer;
Discuss any potential sources of error.
mL solution/g polymer
NaCL (g/L)

7. Task 2: Your Plans
Task 2: Quantify the mass of copper (in Cu form dissolved in water) that sodium polyacrylate can absorb per gram of this polymer as a function of time.
Mass Cu2+/g polymer
In your groups, share your ideas about how to solve this problem, and come up with a common plan that your group will implement.
Once you have a plan, share it with your lab instructor and the rest of the class.
EXPECTED OUTCOME
Time (min)

8. Your Second Challenge
Quantify the mass of copper (in Cu2+ form dissolved in water) that sodium polyacrylate can absorb per gram of polymer as a function of time.
Available resources:
0.25 g of polymer;
100 mL of 0.05 M Cu(NO3)2
Tea bag;
Absorption spectrometer;
Stopwatch;
Magnetic stirrer and stir bar;
Volumetric glassware.
You have 45 minutes

9. Claims, Evidence, and Reflection
Present your claims and evidence to the class. Decide as a group which data should be shared to facilitate the analysis.
Collectively analyze the data and discuss what they tell you about the absorption properties of the polymer;
Discuss any potential sources of error.
Mass Cu2+/g polymer
Time (min)

10. Task 3: Your Plans
Task 3: Pose a research question to investigate in the lab, and design and implement and experiment to answer it.
In your groups, share your proposed research questions and your ideas about how to find the answer.
Select a research question for your group and design a experiment to answer it.
Once you have a plan, share it with your lab instructor and the rest of the class.

11. Implement an experiment to answer your research question.
Your Third Challenge
Implement an experiment to answer your research question.
Available resources:
1.0 g of polymer;
NaCl, Cu(NO3)2, Ni(NO3)2, Co(NO3)2 solutions;
Solid CaCl2;
FD&C Dye Blue #1 and FD&C Dye Red #40 solution;
Absorption spectrometer;
Stopwatch, etc.
You have 45 minutes

12. Claims, Evidence, and Reflection
Present your claims and evidence to the class. Decide as a group which data should be shared to facilitate the analysis.
List and discuss the specific things that you have learned about the absorption capacity of the superabsorbent polymer investigated in this lab.

13. No Report for this Week Your Comments
Discuss in your groups the strengths and weaknesses of this lab, and write down your group suggestions to help improve it.