I usually wait until I have a pretty steady group of regular scientists coming to my programs before I do a polymer-themed program, but I just couldn’t resist. Not only are polymers just the coolest thing in the world, but they also lead to really fun hands-on experiments and demonstrations.
Polymers can be found just about everywhere – in places you might not even have realized. They are in natural materials like wool and silk (among many others), and then also in many man-made synthetic materials like nylon and rubber. [A rubber duckie, for example, is made of synthetic polymers.] Even the double-helix strand of DNA is a form of a polymer known as a “biopolymer.” But what exactly is a polymer?
The youtube video above, uploaded by TTScienceClub, does a great job of graphically showing the basic formation of polymers and linked polymer chains. The word polymer means “many parts.” The individual parts that actually combine to form a polymer chain are called monomers. Sometimes a substance can actually help polymer chains link together and form a more solid substance.
Our SEC scientists had the opportunity to test out polymers with two fun experiments: “Diaper Magic” and “Goo!”
Experiment #1. “Diaper Magic”: Diaper polymers vs. Polymers from Steve Spangler
- Diapers (we used Seventh Generation size 3 diapers)
- Dark colored construction paper
Gallon-sized zip-top plastic bags
- Clear plastic cups
- Plastic spoons for stirring
I love this experiment so much. For some reason, even just discussing diapers completely grosses out all of our SEC scientists – and they certainly don’t want to touch them. I think too many of our scientists are used to helping their parents change younger siblings out of dirty diapers, so it’s hard to examine diapers from a scientist’s perspective 🙂
We’ve all seen diaper commercials on TV, where one brand after another claims to be the “most absorbent.” But what makes a diaper so absorbent in the first place? Is it the cotton stuffing? Not really. It’s one of the many uses of modern polymers. Tiny, super-absorbent polymers no larger than a grain of sand are mixed into the cotton lining the inside of each diaper. These polymers, called polyacrylic acid, are designed to attract water molecules. Each polymer can absorb about 30 times it’s weight in water! All said, most modern diapers can absorb about a half cup of water.
Well, our SEC scientists got a chance to test this out! Steve Spangler’s website provides a great description of this experiment, along with the following how-to video:
Each scientist received their own diaper. We cut into the lining, pulled apart the cotton, and shook the polymer grains onto a piece of colored construction paper (to make it easier to see the white polymers). To make sure we got as many polymers as possible, we also pulled the cotton lining from the diapers, sealed it in gallon sized plastic bags, and shook it for a few minutes. [You’ll be surprised at how many more polymers you can get by doing this additional step!] We poured the polymers into a clear plastic cup, and then added water 1/4 cup water. I also put water bottles on the tables so our scientists could add additional water in small increments to see how much water the polymers could actually absorb. The result? The polymers absorbed the water, and congealed to form a squishy, gel-like substance. If the gel-like substance is powdery and loose, it can still absorb water; if the substance is moist, you’ve already reached the capacity of the polymers you collected. Many of our scientists all pushed their polymers to the limit and ended up with a substance that was definitely more moist and liquid than it started out as.
I believe that if you leave the cup full of squishy polymers on a counter top for a few days (or longer) and allow the water to evaporate, the polymers should return to their original state…what do you think?
For some added fun, we compared the polymers we extracted from the diapers with a pure, straight-from-the-bottle version of super-absorbent polymers that I obtained directly from Steve Spangler Science. The result? The cups with the Spangler polymers actually had a smoother version of the “gel” that forms than our cups with the diaper polymers. Our theory as a group was that cotton filling from the diapers actually mixed into the “diaper gel,” which created a less smooth texture. Though we agreed that both polymer sources seemed equally absorbent.
Experiment #2 Goo!
- 1/4 cup glue (we used white, but clear glue should work as well)
- 1/4 cup water (we used tap water)
- 1/4 cup liquid starch (you can find this in most supermarkets, but you can also order liquid starch online from sites like Amazon.com)
- Paper or plastic disposable bowls (I used plastic, but you can use a lined paper bowl – it just needs to handle liquids well)
- Plastic spoons for stirring
- Food coloring optional (I chose NOT to use food coloring…food coloring and library program rooms never mix well 🙂 )
Our second experiment involved every scientist’s favorite concoction: GOO! There are many different goo (or slime) experiments available online. We based our goo on a formula provided by Science Bob that is equal parts water, liquid starch, and glue. We specifically used 1/4 cup of each item in our mix. [Though we didn’t do this the day of our program, food coloring can be added during the early stages to make goo of a specific color.] First we stirred together the water and glue in a small bowl. You know the glue and water are combined well when it looks like you have a thick, milky liquid in your bowl. We then slowly added the liquid starch. The starch is the key goo ingredient; it is the substance that binds together (links) the polymer chains present in the glue and gives us our slimy, elastic goo substance. The more you stir the three ingredients together, they better they combine. Our SEC scientists loved the goo, especially since it is solid enough to pick up in your hands, stretch, and pound.
Below is a peek at our scientists in action. See you next month for some more science fun at Prosser Library!