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Testing Water Tension

Testing Surface Tension

Why can some insects walk on water? Students will learn about surface tension and illustrate a water strider staying afloat.

Lesson Plan

Supplies Needed

Gather all the supplies needed to bring your craft ideas to life! From paints and markers to glue and scissors, our crafts section has everything to spark creativity and make every project truly special.

  • Cup or Bottle
  • Paper
  • Water
  • Water Dropper

Steps

  • Step 1

    Have students learn about cohesion and surface tension. Surface tension is the result of cohesion among water molecules and explains why water can extend slightly above the rim of a container without spilling. Students can test this by filling a small cup to the rim with water, then adding more water, drop by drop, until a small dome-like shape appears over the rim. Surface tension also explains why some insects can walk on water. 

  • Step 2

    Ask students to investigate insects, such as the water strider, that use surface tension to walk on water. Water striders are small, thin-bodied insects with three sets of legs. Their legs have tiny hairs that repel water and capture air. Repelling water allows them to stand on the water, and the captured air allows them to float and move easily. 

  • Step 3

    Have students look at images of water striders and use the images to guide and inspire them as they create an illustration of a water strider standing on water.

  • Step 4

    When their illustrations are complete, have them present their art to the class and discuss some of the facts they learned about water striders and surface tension.

Standards

SCI: Convey designs through sketches, detailed drawings, or physical models to communicate ideas and solutions.

SCI: Make observations and measurements to identify properties and patterns.

Adaptations

Scientists are studying the legs of water striders in order to make materials that will repel water and help objects to move faster over water. This is an example of biomimicry: the practice of copying strategies in nature to solve human challenges. Have students investigate other examples of biomimicry. For example, studying photosynthesis contributed to the invention of solar panels, and the Stenocara beetle, a desert dweller with tiny bumps on its shell, is able to collect and channel condensed water into its mouth. This helped scientists design materials that collect water from the air more efficiently.

Have students learn some facts about other insects that can walk on water. For example, the great raft spider, one of the largest arachnids in the world, cannot only walk and even run across water; it can also dive and stay underwater for over 10 minutes. And the dark fishing spider waits for fish to come to the surface, then grabs them with their powerful jaws.