Shy Pepper

A simple and amazing experiment to entertain your child

Safe­ty pre­cau­tions

None.

Reagents and equip­ment

  • fresh­ly-ground pep­per;
  • plate;
  • wa­ter;
  • cot­ton swab;
  • liq­uid soap.

Step-by-step in­struc­tions

Fill the plate with wa­ter and grind some black pep­per into it; the pep­per should float on the sur­face. Ap­ply some liq­uid soap to one end of a cot­ton swab, then dip the soapy swab in the wa­ter. Ob­serve as the pep­per “es­capes” to the edge of the plate. To re­peat this ex­per­i­ment, rinse the plate thor­ough­ly and re­fill with fresh, non-soapy wa­ter.

Process de­scrip­tion

Wa­ter’s strong sur­face ten­sion sus­pends the ground pep­per par­ti­cles on the wa­ter’s sur­face. The sur­fac­tants con­tained in soap re­duce this same sur­face ten­sion. The wa­ter pulls the pep­per away from the spread­ing soap film be­cause the force of at­trac­tion be­tween wa­ter and pep­per is greater than that be­tween soap and pep­per.

Try it