Surface tension is a property of liquids that results from the cohesive forces between liquid molecules. It is defined as the force acting per unit length along an imaginary line drawn on the liquid surface, perpendicular to this line. Surface tension causes the liquid surface to contract and behave like an elastic membrane, which is why droplets form spherical shapes and insects can walk on water.There are several methods to measure the surface tension of a liquid. One common experimental method is the capillary rise method.Capillary Rise Method:1. Choose a narrow glass tube capillary tube with a small diameter.2. Clean the tube thoroughly to remove any contaminants that may affect the measurements.3. Immerse the tube vertically into the liquid whose surface tension needs to be measured.4. Observe the rise or fall of the liquid inside the tube compared to the liquid level outside the tube. The liquid will rise in the tube if its surface tension is greater than the tube's material, and it will fall if its surface tension is lower.5. Measure the height h of the liquid column in the tube.6. Measure the radius r of the tube.7. Determine the density of the liquid and the acceleration due to gravity g .8. Use the Jurin's Law formula to calculate the surface tension of the liquid: = ghr / 2Factors affecting surface tension:1. Temperature: Surface tension decreases with an increase in temperature. This is because the kinetic energy of the molecules increases, reducing the cohesive forces between them.2. Impurities: The presence of impurities or dissolved substances can either increase or decrease the surface tension, depending on their nature. For example, surfactants can reduce surface tension, while salts can increase it.3. Pressure: Surface tension is not significantly affected by pressure changes, except in the case of highly compressible liquids like gases.4. Molecular structure: The molecular structure of the liquid and the strength of the intermolecular forces e.g., van der Waals forces, hydrogen bonding play a significant role in determining surface tension. Polar molecules with strong intermolecular forces tend to have higher surface tension than nonpolar molecules with weaker forces.