Which of the following substances lowers the surface tension of water?
Answer Details
Detergent lowers the surface tension of water.
Surface tension is the property of water that causes it to form droplets and resist external forces that can break those droplets apart. It's due to the cohesive forces between water molecules. However, when a substance is added to water, it can disrupt these cohesive forces, which lowers the surface tension of water.
Detergent contains molecules that have both hydrophilic (water-attracting) and hydrophobic (water-repelling) regions. When added to water, the hydrophobic regions of detergent molecules will orient themselves towards the air-water interface, while the hydrophilic regions will interact with the water molecules. This reduces the cohesive forces between water molecules, leading to a decrease in surface tension.
Metal, sand, and paper do not have properties that lower surface tension. Metal and sand are insoluble in water and do not interact with water molecules in a way that lowers surface tension. Paper is made of cellulose, a hydrophilic material that does not disrupt cohesive forces between water molecules.