Exploring surface tension

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Exploring surface tension

This experiment explores a variety of scientific concepts all stemming from the core concept of surface tension. But how are we meant to understand these extended concepts when we don’t even properly understand surface tension? Let’s take it back to the basics to develop and extend our knowledge.

The Surface Tension Introduction Experiment encourages independent decision making and a basic level of comparative analysis through an exploration of the unique properties of water.

Materials

  • Water
  • Cooking oil (We used peanut oil)
  • Syringe or eye dropper
  • Tooth pick
  • Wax or baking paper

Method

Exploring surface tension with oil and water on wax paper. A simple experiment for kids.

  1. Drop a few drops of water onto the wax paper using the syringe.
  2. Discuss the shape of the droplet and any other qualities noticeable.
  3. Drop a few drops oil next to the water again using the syringe.
  4. Compare the liquids by identifying their similarities and differences.
  5. Gently poke the water droplet with a toothpick to further investigate.
  6. Follow the previous step with the oil.

*Even more fun can be had when experimenting with other liquids in the pantry! Try dropping some honey, dish soap or milk onto the wax paper. Do they bind together like the water or separate like the oil? Why/why not?

The Science

This experiment is displaying properties of surface tension in water and we can contrast these with the less dense quality of oil. Surface tension prevents the water molecules from spreading out like the oil does. Water molecules attract each other and tend to stick together, causing the water drop to remain in a dome shape even when poked with the tooth pick. The oil on the other hand, has molecules that don’t attract and stick together and is therefore why the liquid spreads on the wax paper.

The surface of the water drop appears to have a skin-like layer on it called surface tension. It is the way the molecules cling together that causes the water to retain the dome shape on the wax paper.

Experimenting with various liquids will show that the surface tension of each liquid is different. More drops of water can be added until the surface tension is not strong enough to counter the gravitational pull on the water. Even the size of the drops of liquid will differ between liquids.

Kids can explore surface tension with this simple experiment using oil, water and wax paper


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