Alpha science classroom： Build a Water Strider

Have the children seen water striders (also called water bugs, water skiers, water striders, etc.) in the wild? They are bugs that jump easily on the surface of ponds, lakes, and rivers. How can they be unsinkable? Today, the alpha science classroom teaches children to Build a Water Strider, and children can try to find out the answer from this children's physical science experiment project! At the same time, learn the knowledge of force and tension from this interesting kid's science experiment, and unlock the mysteries of science.

Alpha Science Class: Build a Water Strider, Required Materials

• Thin line. You can buy "magnet wires" or thin copper wires at hardware stores, or cut old cables (such as mobile phone chargers).

• Scissors

• Wire strippers (only needed when cutting old cables and need to remove the insulation)

• Shallow dish or bowl

• Water

Alpha science classroom: Build a Water Strider, a step-by-step tutorial.

Step 1: Preparation. If children need to cut old cables, please use wire strippers to strip off the insulation. If you don’t know how to do this, you can ask your parents for help. There may be multiple smaller wires inside the cable, and these wires may also have insulation. Pull the wires apart and strip off all insulation until you pull them onto the bare metal. If you do not have wire strippers, you can ask an adult to carefully scrape off the insulation with scissors or a sharp knife, but be careful not to cut the entire wire.

Step 2: children fill a shallow dish or bowl with water, and cut three threads, each about 8-10 cm long.

Step 3: children twist the wires in the middle tightly to form the body of the insect. The ends of the wires should form the bug’s six legs, three on each side. Spread your legs to evenly distribute the weight of the water strider.

Step 4:  children bend each leg of the water strider into a long and shallow "U" shape. When you place the water strider on a flat, sturdy surface, it should be evenly placed on all 6 legs (for example, none of the legs should be suspended in the air), and your body should be off the ground. If necessary, adjust the outriggers.

Step 5:  children gently put the water strider into the bowl/water tray and observe its changes.

Step 6: If the children's water strider sinks, try to adjust the legs. Remember to make sure that all six legs are in contact with the water at approximately the same time, and that the weight of the bug is evenly distributed.

Step 7: If it still doesn't work, try to adjust the shape of the legs. You want as many wires as possible to come into contact with the water, so make sure they have long, very soft curves and no sharp bends. Once you let it float, watch carefully where the legs touch the water. What do you see?

Step 8: Try to shake the bowl/tray to make waves, or sprinkle some water on the top of the water strider to simulate rain.
Alpha science classroom: Build a Water Strider, the science behind it

If children take a look at the water strider, at first you might think it floats in the water like a boat. However, if you look closely, you will find that it is on the surface of the water and has not actually broken through the surface. How can this be? This depends on a force called surface tension. When water striders contact water, surface tension acts on their legs. Surface tension is the "pull force" on the water surface because water molecules are slightly attracted to each other. Surface tension is the cause of many interesting phenomena, such as how bubbles form, how water forms droplets, and how plants absorb water from the ground (for a list of other interesting items involving surface tension, see the other resources section). In this case, surface tension will form a thin "film" or skin on the surface of the water, making it difficult for very small and light objects to penetrate.

Every object is pulled down by its own weight. If the upward pulling force of the surface tension is enough to equal the weight, the objects on the water surface can be kept above the water surface. Objects that are fully or partially submerged in water, such as boats, are pushed up by buoyancy, which is equal to the weight of the water they displace. If the buoyancy is greater than the weight of the object, it will float. Generally, materials that are denser than water (more mass per unit volume), such as metals, will sink. However, metal boats can float because their hulls are shaped so they can drain a lot of water (that is, there is a lot of empty space inside the boat). In this project, you made a model water strider using metal wire and a saw. You can use surface tension instead of buoyancy to make the metal float.

If you carefully observe where the bug’s legs touch the water, you should see that they have left small “dents” on the surface of the water. This is what causes the surface tension to pull up on the legs. Imagine a group of people grabbing the edge of the bedsheet and pulling it tight. The sheets are flat and level, so at first, it's hard to imagine how it pulls things up. Now imagine throwing a ball in the middle of the sheet. The bed sheet will tilt down slightly, but the person pulling the bed sheet (surface tension) will prevent the ball from falling. Surface tension acts on the legs of the water strider in a similar way.

Finally, if you try to use a thicker wire or paper clip to make a water strider, it may be much more difficult, or even impossible! This happens because surface tension has a relatively strong effect on very small, lightweight objects. This is why the water strider is so small that you cannot walk on the water. Even if you try to open your arms and legs, you will still break through the surface.

Well, now children can observe the water striders they have made, use their imagination, and explore the state of water striders in different liquids through this children's physical science experiment! I hope that this kid's science experiment project in the Alpha science classroom can open a door for children to learn physics and grow into the smartest physicists!

alpha science toys designed many children's physical science experiment kits for children, using various magical and interesting scientific phenomena to create a dreamy scientific world for children, and grow up happily!