Chemical snakes worksheet

Uses for alginate range from the food industry to wound dressings, medicines and the dental industry where it is used as an impression material. Calium alginate is used in dressing for slow healing wounds, such as ulcers which continue to bleed for a long time. When in contact with body fluids, such as blood, calcium alginate exchanges sodium ions for calcium ions. Calcium ions are part of the natural clotting mechanism of the body and therefore assist in clotting of the blood and encourages healing.
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Alginate is a common food additive, it can be identified on the label by the symbol E400. It is used as a thickener, stabiliser and gelling agent, found in ice cream and most other foods that require a thickening agent.

Sodium alginate is a polymer composed of carbohydrate molecules linked end to end. It is extracted from brown seaweed and kelps where it is used as one of the structural polymers that build the cell wall of these plants.

When sodium alginate is put into a solution of calcium ions, the calcium ions replace the sodium ions in the polymer as shown on the right.

Each calcium ion can attach to two of the polymer strands. This is called cross-linking and is shown by the simple animation on the right.

1) Why does the calcium ion replace the sodium ion?

2) Why are cross links formed between the polymers and the calcium ion and the sodium ion?

3) Place some of the snakes in a solution of sodium chloride (salt solution). What do you observe? Can you explain what is happening?

4) Find five foods that contain sodium alginate. Why was sodium alginate added to each food?

The uses of alginate in the food industry are many. Consider the caviar on the spoon pictured on the right. What they really are are spheres of calcium alginate.
Remember the stuffed olives you would eat. The olives with the carrot stuffed inside. Well that is no carrot. It is calcium alginate.
Gaviscon is an over the counter medication for heartburn. It contains alginate. Research why alginate should be present in this medication and how it works.