INSTANT EXPANDING SNOW Contents: Snow polymer powder Plastic cups (100ml) Measuring spoon (5ml) 180ml 25 5 Students prepare amazing, fluffy white snow from a dry polymer and water. PROCEDURE (for 20 students) 1. Add the snow powder to easily accessible containers and have each student measure 1.5 teaspoons (7.5 ml) snow polymer to a 100ml plastic cup using the measuring spoon. As accurately as possible! (Show them how to measure one level and one half teaspoon) 2. Place the cups on paper sheets, disposable plates or plastic trays. 3. Each student now adds a full cup of water (100ml) as quick as possible to the snow powder. It should be done in less than a second!! 4. See a snowstorm erupting! The 7.5 ml should expand in volume to 300ml snow! A note on the water: As the absorption process is an osmotic process, the best absorption will be with water at 20°C and as clean as possible from dissolved salts. First try the reaction with tap water - it should work OK. If not, get distilled water. FURTER INVESTIGATION: j Freeze the snow in a press-seal bag; j What happens when more water is added? (A gel forms - very similar to polyacrylates in nappies) j Make coloured snow by adding 3 drops food colouring to the 100 ml water. j Sprinkle table salt on the snow. The snow releases the water after a few minutes through a process of reverse osmosis. j Experiment with different water qualities. Vary the pH and the salt content and record the yield each time. WHAT IS HAPPENING? Instant snow is a sodium salt of a crosslinked polyacrylic acid. It is used as artificial snow on ski slopes and film sets. It easily expands to 40 times its original volume or can soak up water to more than 100 times its own mass. Industrially it is used for spill containment and as blood absorber in hospitals. The crosslinked molecules have a high sodium content and absorb water through a process known as osmosis and expand as the water moves in. In this process water passes through a membrane to an area with higher salt and lower water concentration. (Place raisins in water to demonstrate osmosis to students (leave for 24 hours)) DISPOSAL Do not dispose of the snow. Keep for next year. But if you have to: Dispose of the instant snow in the waste bin. Do not wash down the drain with water. It is non-toxic and bio-degradable. SAFETY Sodium polyacrylate is classified non-hazardous. See the MSDS on our website. The dry polymer may be irritating to the eyes and skin. If necessary wash affected area under running water. Obtain medical attention if the irritation persists. Ingestion of the dry polymer may be harmful. If ingested, induce vomiting immediately. Seek medical attention. The snow polymer is slippery when wet. Keep off walking surfaces and clean all spills immediately. Copyright Prof Bunsen Science, 2006 www.profbunsen.com.au