Question: Sodium alginate is isolated from seaweed and is used in molecular gastronomy. In the prese — Polymer Chemistry and Intermolecular Forces Chemistry Question
Problem Context
Question: Sodium alginate is isolated from seaweed and is used in molecular gastronomy.
In the presence of certain cations, the polymer can create cross-links and gel spheres are formed. You will be provided with a solution of sodium alginate and three solutions each containing one of the following compounds; calcium chloride, magnesium chloride or potassium chloride. Determine which cation produces the strongest cross-links in the polymer to form hydrogel spheres.
Safety: do not taste or consume the produced liquid spheres
Give a brief description of your experimental plan.
Model Answer
Suggested Experimental Plan and Expected Results: Students should plan to drop sodium alginate solution into different solutions of cations. The best plan would be to create dilution series of cations at varying concentrations and determine the minimum concentration for spherification. Students could also dilute the sodium alginate to determine the minimum concentration for spherification.
Record your data/observations.
Model Answer
Results from UMW Student Undergraduate Research Student Iaroslavna Kovalenko:
Calcium: Well formed spheres occur at concentrations as low as 0.1 M. Spheres formed in concentration of calcium between 0.09 and 0.04 M were softer and could be easily disrupted. Spheres did not form at concentrations lower than 0.04 M. Varying concentrations of sodium alginate dropped into 2 M calcium chloride solution: Spheres with concentration 1-2% sodium alginate were strong and elastic, whereas spheres formed from 0.1-0.9% sodium alginate were soft and could break easily.
Magnesium: Under varying concentrations of magnesium and sodium alginate, spheres do not form. Rather, sheets or films were observed in the solutions.
Potassium: Spheres do not form with the concentrations of solutions formed.
The cation that creates the strongest cross-links in the alginate polymer is ….
Based on the structures of the polymer and cations, briefly explain your experimental observations and the observed differences in cross-linking/spherification.