Experiment with water drops to see how molecules stick to themselves! Delicate Water Striders take advantage of surface tension.

• 1.

  Did you know that water molecules stick to each other? This characteristic is called cohesion. Try experiments to see what happens!

• 2.

  Cover your science area with newspaper. Fill a cup of water to the top. With a plastic dropper, add a few drops of water. Do you see how the water bulges over the top without spilling? The surface tension holds those additional drops. Keep adding drops until the tension breaks and spills over.

• 3.

  Compare how water tension reacts on different surfaces. Thickly color a small area of paper with Crayola Twistables®. Pile up water drops on the colored area and also on the plain paper. Which holds more drops before the surface tension breaks?

• 4.

  Insects called Water Striders use the surface tension of water to their advantage. They hunt prey by skimming the surface of still water. Find a picture of a Water Strider. Look at how its delicate feet pads rest on top of the water. Can you see how the water’s "skin" actually sinks under the insect’s light weight? Draw a Water Strider to show how it stands on the water’s surface.

Standards

• LA: Read and comprehend informational texts, including history/social studies, science, and technical texts, at the high end of the grade level text complexity band independently and proficiently.
• LA: Write informative/explanatory texts to examine a topic and convey ideas and information clearly.
• LA: Engage effectively in a range of collaborative discussions (one-on-one, in groups, and teacher led) with diverse partners on grade level topics and texts, building on others’ ideas and expressing their own clearly.
• LA: Report on a topic or text, tell a story, or recount an experience with appropriate facts and relevant, descriptive details, speaking clearly at an understandable pace.
• MATH: Solve problems involving measurement and conversion of measurements from a larger unit to a smaller unit.
• SCI: Obtain, evaluate, and communicate information about the types of habitats in which organisms live, and ask questions based on that information.
• SCI: Obtain information that animals have structures that allow them to respond to stimuli through instinct or memory.
• VA: Intentionally take advantage of the qualities and characteristics of art media, techniques, and processes to enhance communication of experiences and ideas.
• VA: Select and use the qualities of structures and functions of art to improve communication of ideas.

Adaptations

• Possible classroom resources include: Animals That Walk on Water by Patricia A. Fink Martin; A Drop Of Water: A Book of Science and Wonder by Walter Wick
• Organize a trip to a local pond to allow students the opportunity to see water in action. Ask students to bring their sketch books and Crayola Colored Pencils to sketch what they see. Upon returning to the classroom, bring some of the pond water in a bucket. Use a school microscope to investigate a drop of pond water. Students sketch what they see under the microscope. Compare and contrast a drop of pond water with a drop of water from a classroom faucet. Have students discuss the differences in small groups.`
• What is surface tension? Students collaborate in small groups to develop a definition of this science term. What elements weaken surface tension? Encourage students to gently sprinkle crayon shavings on top of water. Do they float? Why or why not? Squeeze a few droplets of liquid soap into the water. Where do the crayon shavings go? Discuss what happened with classmates and hypothesize why.