Science with Shields: Episode #90 – Surface Tension Penny

Science with Shields

ALTOONA, Pa. (WTAJ) — In this episode of Science with Shields, Christy Shields shows you how surface tension works using water and a penny.

What you need: 

  1. Glass of water
  2. Eye dropper
  3. A Penny

Instructions:

Lay your penny on a flat surface. Next, fill your eye dropper up with water. Now start putting droplets of water onto your penny. When the water gets to the edge, carefully add more drops of water. Observe how a dome of water forms on the penny. Try and count how many droplets of water will fit on your penny before the water runs off.

Science

In this experiment, we are showing how cohesion or surface tension works. Cohesion is when molecules are attracted to other molecules. In this case, hydrogen molecules are attracted to oxygen molecules. This allows the water droplets to bond together. When they bond together, it allows you to continue to add more water on top of the penny because they are bonding together and creating a dome. When talking about cohesion with water, we call that surface tension. Eventually the surface tension breaks, and the water will fall off the penny. Let us know how many water droplets fit on your penny! We were able to fit 29 on ours!  

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