Viscosity and surface tension are the physical properties of the liquid. Viscosity is defined as the resistance offered by the layers of the fluid, while surface tension is defined as the resistance offered by the surface of the liquid to penetration.
Surface tension is the amount of energy required to increase the surface of the liquid by unit area. In other words, it is also the property of the liquid surface that resists force. Surface tension is sometimes seen in terms of energy. More is the surface tension, more is the energy and thus, to minimize energy, the fluids assume the shape with the smallest surface area.
Viscosity is the resistance of a fluid to flow. For example, oil has a high viscosity, but when we put it in the car and heat it, it becomes less viscous and thus flows smoothly through an engine and other parts of the car.
Effect of temperature on surface tension and viscosity
As the temperature increases, viscosity decreases. Surface tension decreases with an increase in temperature. So these are the effects of temperature on viscosity and surface tension. In general, surface tension decreases when the temperature increases because cohesive forces decrease with increased molecular thermal activity. The influence of the surrounding environment is due to the adhesive action liquid molecules have at the interface.
- Increasing temperature results in a decrease in viscosity because a larger temperature means particles have greater thermal energy and are more easily overcome the attractive forces binding them together.