Cellulose fibres can be made by extrusion from a solution of dissolved cellulose
This experiment should take an hour, to an hour and a half.
Items from the junk list – this must include items that allow the gel to be extruded i.e. syringes, cake icer, washing-up bottles.
Materials per group
- 880 Ammonia solution, 300 cm3
- Powdered copper carbonate, 30g
- Cellulose, 6g
- Sulfuric acid, 1 mol dm–3
- Small fresh egg
- Deionised water
Equipment per group
- Beakers, 250 cm3, x2
- Glass rod
- Shallow plastic tray (to extrude the cellulose into)
- Safety glasses
Health, safety and technical notes
- Read our standard health and safety guidance here.
- Wear eye protection.
- This is an open-ended problem-solving activity, so the guidance given here is necessarily incomplete.
- 880 ammonia is a respiratory irritant – work in a well ventilated laboratory or use a fume cupboard. See CLEAPSS HAzcard HC006.
- Copper carbonate is harmful if swallowed, and toxic to aquatic life. See CLEAPSS Hazcard HC026.
- Sulfuric acid is an eye and skin irritant. See CLEAPSS Hazcard HC098a.
This problem caused much consternation during trialling because it is more difficult than it seems. The trick is to get the recipe right and to make fairly thick fibres. These will lift an egg if used carefully, although the fibres degrade after a while.
Using cotton wool as the source of cellulose was found to give the best results.
In the trials, one group cheated first by using a blown egg, and then a small pigeon egg: both were spotted and banned!
The following procedure was found to give good results.
- 10 g of copper carbonate was added to 100 cm3 of 880 ammonia solution in a beaker, until no more dissolved.
- After two minutes, the blue solution was decanted off.
- 1 g of finely shredded cotton wool was stirred in gently, taking extreme care not to fold in air, until the blue solution has the consistency of a shower gel.
- Between 1 and 1.5 g of cellulose was needed.
- Cellulose fibres were reformed by extruding the solution using a 20 cm3 syringe into a 1 cm depth of 1 mol dm–3 sulfuric acid solution in a tray.
- The fibres can be washed with water after 20–40 minutes.
- The ideal fibres are ca 2–3 mm thick, and the egg can be lifted gently by using the fibres to form a cradle.
This resource is part of a collection of problem-solving activities, designed to engage learners in small group work. Find out how to use these resources, and obtain a list of suggested ‘junk items’ here.
Blue copper ammonium solution should be kept for disposal.
Lifting an egg by a thread - student handoutExperiment | PDF, Size 0.25 mb
Lifting an egg by a thread - teacher handoutExperiment | PDF, Size 0.26 mb
The resources were originally published in the book In Search of More Solutions.
This experiment was based on an idea contributed by John Crellin. The procedure outlined was developed by Valerie Tordoff at Eton College.
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