Abraham Lincoln is a Bubbly Chap

  1. Wash and rinse a penny in tap water. Dry it completely with a paper towel.
  2. Place the penny on a flat surface. The flatter the surface is, the better this experiment is going to go.
  3. Use an eyedropper or pipette to draw water and, carefully, drop individual drops of water onto the flat surface of the penny.
  4. Keep track of the water drops as you add them, one at a time, until water runs over the edge of the penny. You’ll probably be surprised by the number of drops you get on there.

Repeat the experiment as many times as you want, or take it further by testing another liquid like vegetable oil, salt water… whatever you want! Use a table similar to the one below to keep track of your trials and liquids.

Liquid / Trial 1 / Trial 2 / Trial 3 / Trial 4 / Trial 5
Water
Vegetable Oil

How Does It Work?

There are two properties at work in this experiment: cohesion and surface tension. Cohesion is the attraction of like molecules to one another. In this case, the like molecules are the H20 molecules in the water drops. Surface tension is a special term we use to describe the cohesion between water molecules.

Water’s cohesion and surface tension are special because of hydrogen bonds. Hydrogen bonds are formed by the hydrogen atoms of one molecule being attracted to the oxygen atoms of another molecule.

The cohesion and surface tension of water becomes apparent when the drops of water you add to the penny reach the penny’s edge. Once the water has reached the edge, you begin to see a bubble or dome of water forming on top of the penny. The bubble shape is a result of the water molecules clinging to one another in an optimal shape (just like the bonds on the surface of a blown bubble).


Any Kid Can Play with Bubbles but a High School Student Learns from It.

  1. Based off of prior knowledge, what does the prefix co- mean? (covalent)

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  1. What is the definition of cohesion?

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  1. What is the definition of surface tension?

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  1. Why are cohesion and surface tension special? What do those bonds do?

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  1. Why does the bubbling effect occur when placing the water on the penny?

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  1. Explain the picture below using the word cohesion.

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Jack Climbing and the Giant Celery Stalk

  1. Cohesion is water’s ability to stick to itself. What is adhesion?

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  1. When working in construction, workers use an adhesive to stick on piece of wood to another. Explain what an adhesive is in your own words.

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  1. Water was being cohesive as it traveled up the celery stalk. It was acting adhesive as well. What was the water sticking itself to as it traveled against gravity?

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  1. When water moves against gravity and into a tiny space, what is it called?

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  1. What are sunflowers being used for in Ukraine. Use the words cohesion, adhesion, and capillary action.

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  1. Think of one more way either cohesion, adhesion, surface tension, or capillary action could be seen or used on Earth.

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