Walking on Water--How Do Water Striders Do It?
Summary
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.
CollapseLearning Goals
This activity is designed for students to get a first look at water tension. It also allows them to make a model and test a situation seen in nature with materials that are readily available.
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:
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
This activity is designed for 3rd graders, but could be appropriate in any grade and possibly as a teacher demonstration in the lower grades. About 30-45 minutes are needed for this activity, but would be best completed after the class has had some exposure to a pond habitat and water striders in nature.
Materials:
-Typing paper
-Pencil
-Scissors
-Drawing of water strider
-Pie tin
-Water
-Paperclips
-Clear glass
-Stopwatch (optional)
Description and Teaching Materials
Procedure:
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.
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
Another interesting water tension activity that could be completed by students while possibly waiting their turn to do the water strider activity is to give each student a penny, a glass of water, and a eye dropper. Students carefully place drops of water on the head of the penny showing the water tension, until the head can no longer hold any more water.
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.
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.
Assessment
Assessment will be through teacher observation and student journaling about this investigation. Classroom discussion about the new vocab terms will also be used.
Standards
3.I.A.1 explore use of science as a tool that can help investigate and answer questions about the environment.
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.
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.