Sodium polyacrylate: a super strong desiccant

How to make an artificial snowdrift and immediately "melt" it

Safe­ty pre­cau­tions

Warn­ing! Only un­der adult su­per­vi­sion

Equip­ment:

  • di­a­pers;
  • scis­sors;
  • ta­ble salt;
  • glass­es;
  • spoon.

Step-by-step in­struc­tions

Cut a few di­a­pers and pour their filler into a glass. Fill a plate with wa­ter and pour the filler on it – the filler ab­sorbs most of the wa­ter and in­creas­es dra­mat­i­cal­ly in size, be­gin­ning to re­sem­ble snow. Fill a glass with this "snow," add three tea­spoons of ta­ble salt, and stir with a spoon – the snow­drift “melts” into a cloudy liq­uid.

Process de­scrip­tion

Sodi­um poly­acry­late’s long mol­e­cules con­tain many car­boxyl groups. These car­boxyl groups at­tract a lot of wa­ter, which caus­es the sodi­um poly­acry­late pow­der to swell and in­crease sig­nif­i­cant­ly in size. This ef­fect is re­versible: when ta­ble salt is added, os­mot­ic pres­sure aris­es, which draws the wa­ter mol­e­cules out of the struc­ture of sodi­um poly­acry­late – yield­ing liq­uid once again!

A sim­i­lar ex­per­i­ment is in­clud­ed in the “Chem­istry of win­ter” set from the MEL Chem­istry sub­scrip­tion.