“Slime” experiment

Kids love to play with slime. It’s like a big piece of chew­ing gum, but you play with it with your hands. It’s like plas­ticine but it doesn’t stick to your hands, doesn’t leave marks on sur­faces and doesn’t keep its form. In our ex­per­i­ment, we’ll show you how to make slime.

Reagents and equip­ment:

• PVA glue (30 g);
• food col­or­ing (2 g);
• sodi­um tetrab­o­rate (5 g);
• beaker;
• dis­tilled wa­ter.

Step-by-step in­struc­tions

Pour 30 g of PVA glue into a small beaker. Then add a small amount of food col­or­ing, and mix un­til a uni­form mass is formed. Add 10 ml of the sodi­um tetrab­o­rate so­lu­tion and mix the re­sult­ing mass. In a few min­utes the mass will thick­en and turn into real slime!

Pro­cess­es de­scrip­tion

PVA glue is an emul­sion of polyvinyl ac­etate in wa­ter, with a plas­ti­ciz­er and spe­cial ad­di­tives. A so­lu­tion of sodi­um tetrab­o­rate (Na₂B₄O₇•10Н₂O), also known as bo­rax, is added to the PVA. When this mix­ture is stirred, the liq­uid grad­u­al­ly thick­ens and turns into a vis­cous slime, a soft rub­ber which you can form and stretch with your hands. The sodi­um tetrab­o­rate in the aque­ous so­lu­tion hy­drolyzes, with the for­ma­tion of an al­ka­li and weak boric acid. And in the al­ka­line so­lu­tion, the PVA trans­forms: it los­es acetic acid and a polyvinyl al­co­hol is formed.

The boric acid then con­nects chains of polyvinyl al­co­hol to each oth­er. A cross-linked poly­mer is formed, which is much more vis­cous and less flu­id than the ini­tial polyvinyl ac­etate (PVA). The re­sult­ing slime has the prop­er­ties of a non-New­to­ni­an flu­id. A non-New­to­ni­an flu­id is a flu­id which some­times be­haves like a sol­id body and some­times like a flu­id. A non-New­to­ni­an flu­id can spread and flow, and can also be sol­id and bounce. The rea­son for this re­sult is that these flu­ids are usu­al­ly made from large poly­mer­ic mol­e­cules, which do not have very strong “ad­her­ence” to each oth­er, so the mol­e­cules can slide over each oth­er rel­a­tive­ly freely.

Safe­ty pre­cau­tions

Don’t let chil­dren put the toy in their mouths. Af­ter play­ing with slime, you should wash your hands. Keep the slime in a clean jar with a lid, in a cold place.

Warn­ing! Sub­stances of this ex­per­i­ment are tox­ic and high­ly dan­ger­ous for your health. Do not try this at home. Only un­der pro­fes­sion­al su­per­vi­sion.