“Gallium heart” experiment

Met­als are of­ten as­so­ci­at­ed with some­thing sol­id and in­de­struc­tible. But de­spite the stereo­type, this met­al will trem­ble as soon as so­lu­tions touch it.

Safe­ty pre­cau­tions

Wear pro­tec­tive gloves and glass­es.

Warn­ing! Only un­der adults su­per­vi­sion.

Reagents and equip­ment:

• gal­li­um (5 g);
• 20% sul­fu­ric acid so­lu­tion (20 ml);
• 10% potas­si­um dichro­mate so­lu­tion (2 ml);
• pipette;
• porce­lain cup.

Step-by-step in­struc­tions

Melt gal­li­um in hot wa­ter and put it in a porce­lain cup. Then pour the sul­fu­ric acid over the drop of gal­li­um and add the potas­si­um dichro­mate so­lu­tion drop by drop. The gal­li­um starts to throb. Over time the throb­bing stops. Add a new por­tion of potas­si­um dichro­mate–and the drop will trem­ble once more.

Pro­cess­es de­scrip­tion

Gal­li­um is a met­al which turns liq­uid at 29.8 °С, so it can even melt in the hand. When it re­acts with sul­fu­ric acid, it be­comes cov­ered with gal­li­um(III) sul­fate. The sur­face ten­sion of the drop in­creas­es, and it con­tracts into a ball. When potas­si­um dichro­mate is added, ox­i­da­tion-re­duc­tion pro­cess­es take place, which have still not been ful­ly ex­plained by sci­en­tists. As a re­sult, the film of gal­li­um(III) sul­fate dis­in­te­grates, the sur­face ten­sion de­creas­es, and the drop spreads out. The process re­peats un­til all the potas­si­um dichro­mate runs out.