Walking on Water--How Do Water Striders Do It?
In this interactive demonstration, students will make a paper model of a water strider and enable it to stay on the surface of a glass of water through the surface tension of the water.
Students will also get a lesson in patience and steady hands as they carefully place paperclips in the glass of water to make the water level rise above the glass and create surface tension.
Concepts: Water molecules like to stick close to each other, showing a force called cohesion. Where the water molecules meet the air, their cohesion creates surface tension. This surface tension creates a thin skin on the water. This skin on the water is strong enough to support lightweight objects. Animals that walk on water spread their weight over a large area so they won't break through the water's skin.
Vocabulary: water tension, cohesion, water strider, habitat
Context for Use
Materials needed: typing paper, pencil, scissors, drawing of water strider, pie tin, water, paperclips, clear glass, and a stopwatch (optional)
Resource Type: Activities:Classroom Activity:Short Activity:Demonstration
Grade Level: Intermediate (3-5)
Description and Teaching Materials
Lay a piece of paper over the pattern of the water strider, trace the pattern onto the paper with your pencil and cut the pattern out. Bend the feet along the lines so the strider can stand up, and put to one side. Place the clear glass on the pie tin and fill it up to the very top with water. Count how many paper clips you can carefully slip into the water one at a time, making sure your fingers don't touch the water. Once the water is higher than the rim of the cup, carefully place the paper strider onto the water and use the watch to record how long it stays on top.
Taken from: Insectigations: 40 Hands-On Activities to Explore the Insect World by Cindy Blobaum. Chicago Review Press, Inc. C. 2005, pages 81-82.
Teaching Notes and Tips
This activity will be different for me because we will first go to our school's nature area and look at water striders in nature.
3.I.B.1 ask questions about the natural world that can be investigated scientifically.
3.IV.B.1 describe the structures that serve different functions in growth, survival, and reproduction for plants and animals.