How Does It Work
When you make Insta-Worms, you’re learning about the science of polymers. The creative scientists at Steve Spangler Science coined the name Worm Goo, but the real name of this liquid is sodium alginate. Sodium alginate is a long chain of molecules called a polymer. Polymers are large molecules made by linking many smaller molecules together. Specifically, sodium alginate is a polysaccharide isolated from seaweed. Polysaccharides, such as starch and alginate, are made by linking together hundreds of glucose (sugar) molecules. Alginate is commonly used as a thickening agent for foods such as ice cream and fruit pies. Now that you know this chemistry secret, take a look at food labels the next time you’re at the grocery store to find out which other foods contain sodium alginate. Alginate compounds are also used for, among other things, dental impression materials and wound dressings.
The sodium alginate (Worm Goo) immediately changes from a liquid to a solid the moment it touches the Worm Activator solution. The Worm Activator solution contains calcium, which serves to link the long polymer chains together. Scientists call this “cross-linking.” For the scientists in the audience, here’s a more detailed description of what happens: a polymer strand is formed when the sodium alginate solution is added to a calcium chloride solution. This occurs because the Ca++ ions replace the Na+ ions and serve as a cross-linking agent to link two alginate chains together. The resulting cross-linked polymer is insoluble in calcium chloride solution and this results in the formation of the polymer strand. See, now you know!
That still leaves us with the mystery of how the Insta-Worms changed color. The secret behind this fascinating phenomenon is a special thermochromic dye in the Heat Sensitive Worm Goo. Thermochromic means that a color change (chromic) occurs in accordance with temperature (thermo). The color change on the Insta-Worm (it will happen with Worm Goo, too) happens when the temperature of the Insta-Worm reaches a certain temperature (approximately 29º C or 84.2º F). At this temperature, the pigment in the dye reacts by twisting to a new shape, changing the wavelength that it reflects. Thermochromic dyes and inks find use in a lot of objects, from color changing bath toys and coffee mugs, to child thermometers and battery indicators.
