100 Days Project

Nanogirl: Star Science

Nanogirl wants to find 100 friends to do science experiments with her to prove that no matter who you are or what your education level, you can always have fun with science.

Day 34:

Evan makes pepper flow

Evan taught me a new science trick which was really fun to watch and so simple to do with ingredients that are easy to find in the kitchen.

First he filled a bowl with water, then sprinkled pepper into the bowl.  The pepper floated on top of the water and when Evan touched his finger on top of the floating pepper, nothing happened.  Next Evan put a drop of washing up liquid on his fingertip and again touched it on top of the floating pepper.  This time the pepper instantly moved to the edge of the bowl, as if by magic, and created a big circle of pepper free surface in the middle.  It looked like Evan had the power of magic in his finger to command the pepper away!

We know that Evan, as smart as he is, doesn't have magic in his finger, so there must be a scientific explanation.

Adding the washing up liquid lowers the surface tension of the water which makes the water wants to spread out more.  When water is confined to a bowl, it can't reall spread out anywhere so it moves until it reaches the edges of the bowl.  Because the pepper floating on top of the water, it is carried to wherever the water is going to, which in his case is the outer edge of the bowl.  This shows us visually how fast the water spreading occurs and in which direction it goes, and is also really cool to watch.