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Make Your Own Algae Beads
Recommended Grade Level(s):
Appropriate for: 6th Grade–12th Grade
Time Requirements:
Prep Time: 1 month (mostly passive time while culture incubates)
Activity Time: 1 hour (fully prepped)
Teaching Topics & Concepts:
In this procedure you will create a gel-like bead of algae mixed with sodium alginate; a polysaccharide derived from brown
algae (seaweed) that is often used as a thickening agent in food. A drop of this algae mixture will become rigid and "bead-like"
by exposing it to Calcium Chloride. Calcium ions (Ca2+) are exchanged with sodium ions (Na+) and replace them in the poly-
mer. However, unlike Na+ which can form only one bond, Ca2+ can form two. This allows for cross-linking to occur among the
polymer chains which leads to rigidness of the drop and an algae bead as a result!
Materials:
Safety
• Always read the SDS for all chemicals before handling them.
• Wear safety glasses, gloves and lab coat or apron.
!
Procedure:
Day 1—Start Algae Stock Culture
• Pour algae Starter Stock into ~1L flask
• Place in front of a light source (shouldn't get warm to the touch)
• Aerate using an aquarium pump and diffusion stone
• Cover the flask opening with foam/cotton to keep out dust.
• Allow to grow for approximately 4 weeks. Over this time, it will turn dark green.
• As evaporation occurs, add fresh media to the flask to replenish nutrients.
Day 28—Prepare Solutions and Equipment
2% Sodium Alginate (by mass)
• Add 5g of Sodium Alginate to 250 mL water
• Add the alginate to room temperature water while stirring and agitate with stir plate until fully dissolved.
This may require up to 24 hours on the stir plate.
3% Calcium Chloride (by mass)
• Add 7g CaCl2 to 250mL water
• Chill overnight in refrigerator
Start Concentrating Your Algae Stock Culture
• Your solution should now be a dark green. Remove air tube and re-cover with foam/cotton.
• Move the culture to your workspace (room temperature) and allow to sit overnight to settle.
• Distilled water (bottled water is also ok)
• Powdered Sodium Alginate (for 2% Sodium Alginate Solution)
• Stir Plate and Magnetic Stir Bar (for 2% Sodium Alginate
Solution)
• Powdered Calcium Chloride (for 3% Calcium
Chloride Solution)
• Culturing Equipment
– Algae Starter Stock
– 1L flask
– Aquarium pump with tubing and air stone
– Light (ideally full-spectrum)
– Foam/Cotton Plug
• Algae Bead Collecting Equipment
– Ring Stand
– Separatory Funnel
– 500mL flask (or larger)
– Tea Strainer or Spoon
Find materials for this activity at wardsci.com.
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