Magic is a perfect way to get people's attention. However, when I am performing science shows, or presenting in front of my class, I always repeat this mantra, "It's not magic! It's science!" because I want people to realize that there is a scientific explanation behind everything they see. This disappearing water trick is a great way to spur interest, get people questioning and to have a good laugh at the same time.
The chemical used in this science experiment, or magic trick, is sodium polyacrylate which goes by many names: instant snow, waterlock, superabsorbant diaper polymer, water beads and many more. Sodium polyacrylate is (hold your hat, it is about to get super technical) a sodium salt of polyacrylic acid that acts as a cross-linked polymer.
What is sodium polyacrylate in simple terms? It is a polymer, which means it is a large molecule made up of several smaller repeating structures. I like to think of this as an uncooked block of Ramen Noodles (yes, the stuff that you eat). A block of ramen has long noodles sandwiched together into a tight woven pattern and, at an atomic level, sodium polyacrylate has a similar structure. When you put a block of ramen in water, it soaks up the water and expands. Our polymer is a little different, although the visual representation of what happens with the ramen is similar. The main difference is that the polymer has negatively charged molecules on the long chains (think of the long ramen noodles where each of the curls has extra electrons attached) which bonds to water through hydrogen bonds. These hydrogen bonds hold the water molecules in place, causing the sodium polyacrylate to expand and making the water "disappear". This chemical structure allows the polymer to hold up to 300 times its own mass in water!
How do you do the disappearing water trick?
You will need three plastic cups and one cup of water. Add 1.5 teaspoons of sodium polyacrylate to one of the cups before the demonstration. Show the audience that you have a cup of normal water by drinking it and pour a small amount of water into the cup containing the sodium polyacrylate. Add 1/2 cup water to the cup containing the powder. Encourage your audience to keep their eye on the cup of water. Move the cups around, mixing up the order; this will give the polymer time to absorb the water. Then, start flipping cups over and showing that the water has disappeared!
What you'll need:
1 1/2 teaspoons Sodium Polyacrylate (approx. 7 grams)
1/2 Cup water (100ml)
Do diapers have sodium polyacrylate?
Yes! It is woven into a pouch inside the diaper which also contains cotton. The polymer and cotton absorb the baby's "potty" and because of the hydrogen bonds between the water (in the waste) and the sodium polyacrylate, the potty doesn't come spilling out...unless you wait too long to change the diaper...the polymer can only hold so much!
So, is it science or is it magic?
SCIENCE, of course!
Where can I get sodium polyacrylate?
I've provided some links above to help you find and order sodium polyacrylate (click here to order) so you can play with this magical polymer see just how amazing science is for yourself!
The Science Spot on Montana This Morning - KTVQ Billings, MT - CBS
Craig Beals visits Montana This Morning on KTVQ to show the crew the science behind the Disappearing Water Magic Trick.
Keep on Learning! ~Craig
