Testing Water Tension
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.
Adult supervision is required for any arts & crafts project. Observe children closely and intervene as necessary to prevent potential safety problems and ensure appropriate use of arts and crafts materials. Some craft items, particularly beads and buttons, are potential choking hazards for young children. Avoid use of such small parts with children younger than 3 years. Craft items such as scissors, push pins and chenille sticks may have sharp points or edges. Avoid use of materials with sharp points by children younger than 4 years. Read all manufacturers' safety warnings before using arts and craft supplies.
- • Use what you know to amaze your friends and family. Rub a paper clip and then try to float it on water.
- • What elements can weaken surface tension? Gently sprinkle crayon shavings on top of water. Do they float? Squeeze a few droplets of liquid soap into the water. Where do the shavings go? The soap weakens the surface tension, making the water molecules spread out and moving the crayon shavings.
- • Visit a pond to see still water in action.
- • Assessment: Are students actively involved in the investigations? Are their drawings accurate?
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