Activity Time: 10 - 20 minutes
Recommended Grades: 3 - 8
Objectives: Explore and experiment with the surface tension of water. Then, experiment with different liquids as you aim to answer the question: Will it float?

• Bowl filled with water
• Tissue paper, cut into approximately 3” x 3” squares
• Pencil with an eraser
• Paper clips
• Liquid dish soap

1. Fill the bowl with water.
2. Attempt to float a paper clip in the bowl of water. Why do you think the paper clip does not float?
3. Very carefully lay the tissue paper flat onto the water.
4. Very gently place a dry paper clip onto the tissue paper.
5. Using the pencil eraser, push the tissue into the water until it sinks. The paper clip should be left floating. This may take a few tries.
6. Think about the effect of first laying the tissue paper onto the water. What other ways can you lower the paper clip onto the water so that it floats? Can you get more than one paper clip to float?
7. Once the paper clip is floating, add a few drops of liquid dish soap into the bowl of water. What happens?
8. As an extension: Repeat the experiment with different liquids, such as juice or milk. Which liquids have the strongest surface tension?

Water is what is known as a “polar chemical.” This means that each water molecule has positive and negative charges at different ends. These molecules line themselves up so that the negative end of one molecule is next to the positive end of another. The molecules are attracted toward one another, and this creates a sort of “skin” at the surface of the water. Scientists call this “surface tension.” In nature, insects that walk on water are taking advantage of this surface tension. When you initially drop the paper clip into the bowl of water, it sinks, as the paperclip is too dense. By first laying down the tissue paper, you allow the paper clip to be lowered onto the top layer of water without breaking the “skin.” You may notice a slight depression surrounding the paper clip once it is floating. The same can be accomplished by gently lowering the paper clip onto the surface using a fork or a bent paper clip. Adding the dish soap breaks the bonds between the water molecules, thus breaking the surface tension and causing the paper clip to sink.