Which statement best explains how surface tension causes the surface of water to curve?

• A. Surface tension results from cohesive forces between water molecules, pulling the surface molecules inward and causing the surface to curve.
• B. Surface tension is caused by adhesive forces between water and air, which push the surface molecules outward and flatten the surface.
• C. Surface tension is due to ionic bonds forming at the water's surface, forcing it to curve.
• D. Surface tension arises because water molecules at the surface have higher kinetic energy, making the surface curve upward.

Answer: (A)

Verified step by step guidance

1. Understand that surface tension is a physical property of liquids caused by the cohesive forces between molecules at the surface.
2. Recognize that in water, these cohesive forces are primarily hydrogen bonds between water molecules, which pull the surface molecules toward the bulk of the liquid.
3. Realize that because surface molecules experience a net inward force (due to fewer neighboring molecules above), the surface behaves like a stretched elastic membrane.
4. This inward pull causes the surface to minimize its area, leading to a curved or 'meniscus' shape, especially noticeable near container walls or when water interacts with other surfaces.
5. Conclude that surface tension results from cohesive forces pulling surface molecules inward, causing the surface to curve, rather than adhesive forces pushing outward or ionic bonds forming.