The correct option is **B. The temperature of the liquid**. ### Detailed Explanation **Surface Tension Overview:** Surface tension is a physical property of liquids that describes the elastic-like force existing at the surface of a liquid. It arises due to the cohesive forces between liquid molecules. Molecules at the surface experience a net inward force because they are attracted to other liquid molecules below them, leading to a minimized surface area. **Why Temperature Affects Surface Tension:** 1. **Molecular Motion:** As the temperature of a liquid increases, the kinetic energy of its molecules also increases. This increased motion allows molecules to overcome the cohesive forces that contribute to surface tension. Therefore, as temperature rises, surface tension typically decreases. 2. **Phase Changes:** At higher temperatures, liquids may approach their boiling point, where the cohesive forces weaken significantly, leading to a further reduction in surface tension. 3. **Empirical Observations:** Experimental data consistently show that for most liquids, surface tension decreases with increasing temperature. For example, water has a surface tension of about 72.8 mN/m at 20°C, which drops to about 58.9 mN/m at 100°C. ### Why Other Options Are Incorrect or Weaker **A. The liquid's volume** - **Explanation:** The volume of a liquid does not significantly affect its surface tension. Surface tension is an intensive property, meaning it does not depend on the amount of liquid present. Instead, it is a characteristic of the liquid itself. For example, whether you have a drop of water or a full glass, the surface tension remains the same. **C. The shape of the container** - **Explanation:** While the shape of the container can influence the behavior of the liquid (like how it spreads or forms droplets), it does not affect the intrinsic property of surface tension. Surface tension is a property of the liquid itself and remains constant regardless of the container's shape. **D. The atmospheric pressure** - **Explanation:** Atmospheric pressure has a minimal effect on surface tension. While it can influence boiling points and vapor pressures, the cohesive forces between liquid molecules, which determine surface tension, are not significantly altered by changes in atmospheric pressure under normal conditions. ### Summary of Key Points - Surface tension is primarily affected by the temperature of the liquid; as temperature increases, surface tension decreases. - The volume of the liquid, the shape of the container, and atmospheric pressure do not significantly influence surface tension. - Understanding the relationship between temperature and surface tension is crucial for applications in physics and engineering, such as in fluid dynamics and material science. ### Revision Summary - Surface tension is a measure of the cohesive forces at the surface of a liquid. - Temperature significantly affects surface tension; higher temperatures lead to lower surface tension. - Volume, container shape, and atmospheric pressure do not significantly alter surface tension. - Always consider the molecular interactions when studying properties like surface tension.