What property allows water striders to sit on the surface of water?

What property allows water striders to sit on the surface of water?

• A. Cohesion
• B. Adhesion
• C. Viscosity
• D. Density

Answer: (A)

Water striders ride on the surface because of surface tension created by cohesive forces between water molecules. Cohesion pulls water molecules at the surface toward each other, forming a tight, skin‑like film. When the insect’s legs press on that film, the surface tension provides an upward force along the contact line, enough to support the insect’s weight and let it stay on top as its legs distribute the load. Adhesion (water sticking to the legs) can influence wetting but isn’t the lifting mechanism here. Viscosity affects how easily water flows, not whether the surface can support weight. Density concerns sink vs. float, but the key factor enabling sitting on the surface is cohesion-driven surface tension.

Water striders ride on the surface because of surface tension created by cohesive forces between water molecules. Cohesion pulls water molecules at the surface toward each other, forming a tight, skin‑like film. When the insect’s legs press on that film, the surface tension provides an upward force along the contact line, enough to support the insect’s weight and let it stay on top as its legs distribute the load. Adhesion (water sticking to the legs) can influence wetting but isn’t the lifting mechanism here. Viscosity affects how easily water flows, not whether the surface can support weight. Density concerns sink vs. float, but the key factor enabling sitting on the surface is cohesion-driven surface tension.