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Instant Snow Polymer
Sodium polyacrylate is a superabosorbant polymer that is able to expand as it absorbs 300-800 times its weight of water. Commercially, it is found in baby diapers and as a soil additive for its ability to retain moisture. Polysnow is a specific sodium polyacrylate polymer that has been cross-linked to a lesser extent than the sodium polyacrylate found in water beads or diapers. When just the right ratio of water to Polysnow (3g polymer: 60 mL water) is mixed, the polymer impressively expands to a volume greater than the water added. Salt can be added to “flatten” the snow to demonstrate concepts behind diffusion gradients. Younger students will enjoy exploring various options on how to color the snow (before it forms, or after) and how that affects the color mixing.
Materials for Snow-Only Activity:
1. Goggles
2. Polysnow (Sodium Polyacrylate)
4. Wash bottle filled with water (DI preferred, but not necessary)
6. 100 mL plastic graduated cylinder
8. Stirring sticks (2/student)
9. Secondary container for small beaker (to contain mess)
10. Dropper bottles
12. Scoopula
13. Sandwich baggies (if allowed to take home) with labels (do not eat, throw in trash, contains snow polymer ( sodium polyacrylate).
Student Procedure (whole-classroom recommended):
1. Wear goggles.
2. Using a beaker, pour a bit less than 60 mL of DI water to a 100 mL graduated cylinder. Use a wash bottle to accurately squirt the final few mL to the 60 mL mark.
3. Students that have completed that step can confirm the (approximate) accuracy of their measurements by looking at the markings on the beaker.
4. To the small (50 mL) plastic beaker, add 3 g (1.5 Tbsp) of Polysnow).
5. Pour the 60 mL of water from the bigger beaker into the smaller beaker all at once. Liquid level should reach the top. If so, the expanding polymer will overflow into secondary container as it “snows down”
6. They will need time to observe and touch the snow.
7. If time permits, ask the students to measure out 60 mL water again into their larger beaker.
8. Add 5-7 drops food coloring to the beaker and stir. It is most cost-effective to buy the food coloring in bulk bottles and fill our own dropper bottles.
9. Give students another portion of the solid polymer to dump into their small beaker.
10. Add the colored water to the small beaker as before to get color snow.
11. Students can use a jumbo graduated cylinder (500 mL) to collaboratively layer various colors to display their results. A scoopula is a useful tool for transferring the solid into the large graduated cylinder. Allow the layered creation to sit for a week and observe that the colors at the interface are mixing.
Possible Modifications:
1. Destroy the Snow – student grade 3 and older are usually excited to perform some qualitative analysis on the snow. Students can scoop a small sample of their snow to almost fill two test tubes. To the first test tube, add about 17 g table salt (NaCl). To the second test tube, add nothing other than the snow (control). Stir the contents of both test tubes and observe that the one with the salt collapses into a slush as the water exits out of the cross-linked polymer network.
2. Snow coloring methodology – great for below grade 3 - compare the effects of pre-coloring the snow vs. post-coloring. Instead of coloring the liquid, try coloring the snow.
3. Explore the ratio of water added – students in lower grades could add water with the wash bottle and observe how it changes the snow composition/texture. Upper grade elementary students can more systematically prepare different batches of snow using different ratios of starting materials.
4. Measurement focus – Use this activity to supplement a measurement learning objective. Students have to get the right ratio, and measure to the line in the graduated cylinder to get optimum results. Students can be intentionally given smaller graduated cylinders to learn how to use successive measuring to get the desired final volume.
Safety:
Sodium polyacrylate is found in diapers, so it is safe to handle. Students may need to be reminded not to consume, or to be mindful to avoid eye contact and dust inhalation. If students want to take them home, it is recommended that a label is affixed to a plastic bag that can hold the snow.
Cleanup:
The snow hydrogel is safe to go in the regular trash can. Cleanup is easiest if water is avoided. The any mess containing snow will dry out into a powder that is easy to wipe out/sweep up. Adding additional water tends to make the snow more gel-like and results in a much stickier cleanup.
Materials for Snow making and destroying (with salt) Activity
1. Goggles
2. Polysnow (Sodium Polyacrylate)
3. Food coloring
4. NaCl
5. Wash bottle filled with water
6. 50 mL plastic beaker
7. 100 mL plastic graduated cylinder
9. Stirring sticks (2/student)
10. Graduated test tubes with rack
11. Secondary container for beaker (to contain mess)
12. Dropper bottles (3)
13. Red food coloring
14. Blue food coloring
15. Yellow Food coloring
16. 2 L graduated cylinder
17. Ziplock baggies with labels (do not eat, throw in trash,snow polymer ( sodium polyacrylate).
Class-Prep:
1. For large groups, it may be worth measuring the 3 g (1.5 Tbsp) of polymer into separate vials.
2. Pre-fill wash bottles (125 mL) with DI water (1 per student).
3. Pre-fill dropper bottles with food coloring.
4. Prepare lecture size demonstration.
5. Pre-fill NaCl vials
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