Mrs. Mole, a former science teacher
and current substitute teacher at Cherry Valley demonstrates the
principles of adhesion, cohesion and surface tension.
Mrs. Mole filled a cup all the
way to the very top with plain tap water.
She then proceeded to drop paper
clips into the water, one-by-one, asking us to guess how many
paper clips she could put into the cup before the water overflowed
the top of the cup.
ONE HUNDRED AND THREE!!
How can that be?
Through this experiment we explored
water's desire to hold itself together, called cohesion. When
you add objects slowly, one by one, surface tension forms a "skin"
holding the water in the cup. Adding the clips slowly allows the
water "skin" to stretch. We also discussed adhesion
which is the force and result of attraction between dissimilar
molecules (as in the water sticking to the glass)
The final experiment showed
what happened when we "jiggled" or moved the cup. We
broke the surface tension and, of course, the water overflowed