The surface tension of water varies with temperature. As the temperature increases, the surface tension decreases. This is because the increased kinetic energy of the water molecules weakens the hydrogen bonds between them, leading to a decrease in surface tension. Here are some approximate values for the surface tension of water at different temperatures:- 0C 32F : 75.6 mN/m millinewtons per meter - 20C 68F : 72.8 mN/m- 40C 104F : 69.6 mN/m- 60C 140F : 66.2 mN/m- 80C 176F : 62.4 mN/m- 100C 212F : 58.9 mN/mThe addition of solutes such as salt or soap can also affect the surface tension of water. In general, the addition of solutes can either increase or decrease the surface tension, depending on the nature of the solute.1. Salt e.g., sodium chloride : When salt is added to water, it slightly increases the surface tension. This is because the dissolved ions Na+ and Cl- interact with the water molecules, leading to a more ordered structure at the surface, which results in a higher surface tension. However, the effect of salt on surface tension is relatively small compared to other solutes like soap.2. Soap e.g., sodium stearate : Soap is a surfactant, which means it can significantly reduce the surface tension of water. Surfactants have a hydrophilic water-loving head and a hydrophobic water-repelling tail. When soap is added to water, the hydrophobic tails align at the surface, disrupting the hydrogen bonding between water molecules and reducing the surface tension. This is why soap is effective at cleaning and forming bubbles, as the reduced surface tension allows water to spread more easily and mix with oils and dirt.In summary, the surface tension of water decreases with increasing temperature and can be affected by the addition of solutes. Salt typically causes a slight increase in surface tension, while soap significantly reduces it due to its surfactant properties.