Polymer Worms Lab Pack
M11L
Contents
Worm Powder A (Sod. alginate)
Worm Powder B (Calcium chloride)
Plastic cups (100 mL)
Syringe (5 mL)
3 x 4.5 g
20 g
36
12
You will also need
500 mL beaker
3 food colouring solutions
2L bottle / beaker
Measuring cylinder (100 mL)
PROCEDURE (for 24 students)
1. A few hours prior to the activity: Fill the three Worm Powder A bottles containing the sodium alginate
with WARM tap water. Cap, shake well and leave to stand. Shake again before the activity and colour
each bottle with a different food colouring solution (one or two droplets only) - optional. Transfer the
solution in each bottle to 4 cups (included) so that 4 groups of 6 students can have access to the three
coloured solutions.
2. Wear eye protection and dissolve all of the Worm Powder B in 2 liters of water. Any clean 2 liter bottle /
beaker can be used. Label this clearly Worm Powder B solution. This is a 1% solution in Ca2+ ions.
3. Fill 24 cups to 60ml with this Worm Powder B solution and hand to each student. (This volume is not
critical. No need to use a measuring cylinder).
4. Cross-linking the worms: Have the students suck up one Worm Powder A colour at a time with a syringe
and squirt it in a steady even stream into the clear Worm Powder B solution.
5. Flexible, stringy worms will form instantly. Continue with the other two colours while the first stays in the
solution for 1 minute. Then pull them from the cup with your fingers.
6. If the worms break, dip them back into the solution to seal them up. The longer they stay in the solution,
the more rigid they will become.
7. Uncross-linking the worms - teacher demonstration: Prepare a saturated sodium chloride (table salt)
solution (¾ teaspoon salt in 2 teaspoons water). Half fill a test tube with saturated sodium chloride
solution. Drop a worm into this solution and close with a stopper. Shake the test tube and observe.
WHAT IS HAPPENING?
A simple cation exchange reaction!
Sodium alginate is a polysaccharide isolated from seaweed cell walls. It is commonly used as a thickener in
foods such as ice cream and fruit-filled snacks. Polysaccharides are polymers as they are made up of
hundreds of smaller glucose molecules. The sodium alginate immediately changes from a liquid to a solid as
it comes in contact with the calcium solution. The Ca++ ions
replace the Na+ ions in the alginate solution and cross-link two
alginate chains together. The resulting cross-linked polymer is
insoluble in the calcium chloride solution and a polymer strand
forms.
DISPOSAL
Dispose of the polymers in the garbage bin.
SAFETY
Sodium alginate is a food grade chemical. No hazard.
Calcium chloride in solid form is a classified irritant, a hazardous chemical. Download and read the MSDS
on our website. Wear eye protection when handling the solid. The resultant solution is completely safe as it is
only a 1% salt solution. As with all chemicals, instruct students to wash their hands after use and not to taste
or eat the worms ☺.
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