The surface tension of water is 72 dynes per centimeter on average, although variations in temperature may raise or lower surface tension. Dynes are a unit of measure used to indicate the amount of force needed to break surface tension of a liquid.
Surface tension is essentially the strength of the bond that holds the surface molecules of a liquid together. Their molecular structure differs from the rest of the liquid, as they have no molecules above themselves, while the liquid molecules below the surface have neighboring molecules on all sides. The bonds between molecules on a liquid's surface are typically stronger than those underneath. Heating water above a neutral temperature weakens the molecular bonds on the surface and lowers the surface tension.