"Artificial Snow" experiment
How to make snow with water and sodium polyacrylate
Snow in summertime? Impossible, you’ll say. But we say that if you know chemistry, everything is possible. Here’s an experiment where we show you how to make artificial snow!
Reagents and equipment:
- sodium polyacrylate;
- distilled water;
- Petri dish;
- narrow-necked beaker;
- large beaker.
Put 3 g of sodium polyacrylate in a Petri dish and add 15 ml of distilled water. The sodium polyacrylate will start to swell up and turn into “snow”. Also place a small amount of sodium polyacrylate in a narrow-necked beaker and add 100 ml of water. Observe the sodium polyacrylate expand. After several minutes there will be so much of it that it will start to spill out of the beaker.
Sodium polyacrylate is a sodium salt of polyacrylic acid. Its molecules are very long, consisting of identical repeating fragments containing charged groups. Sodium polyacrylate is a very hygroscopic substance, i.e. it likes to absorb water. One of the main properties of the compound is the ability to absorb liquid of 200-300 times its own mass. So it instantly absorbs water and swells up immensely, forming flakes that resemble snow. Why does this happen? The water molecules penetrate between the chains inside the granules of sodium polyacrylate. Each sodium cation Na⁺ puts on a “coat” of water molecules. These “coats” also form around negatively charged centers – the carboxylate groups CO²⁻. Each chain of polyacrylate that is “soaked” in this manner unravels. However, the water in this experiment is not sufficient for all of them, and goes inside each granule. So “dry” chains remain on the outside. From inner expansion, air comes between them, and the total volume increases. If there is too much water, the granules become soggy, stick together and turn into gel – a semi-transparent viscous mass which has a very similar consistency to jelly or aspic.
You can touch artificial snow, but don’t eat it. Don’t forget to wash your hands after touching the artificial snow.
Warning! Only under professional supervision.