"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.

Step-by-step in­struc­tions

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.

Pro­cess­es de­scrip­tion

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.

Safe­ty pre­cau­tions

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.

Try it