So, they are less viscous or have low viscosity.įor Viscosity of fluids, the tangential, or shearing, stress that causes flow is directly proportional to the rate of shear strain, or rate of deformation, the shear stress divided by the rate of shear strain is constant for a given fluid at a given temperature. This is because of the weak intermolecular forces between them. The liquids which flow very slow have high internal resistance. These liquids are less viscous and have low viscosity. This is because of the strong intermolecular forces between the molecules. The liquids which flow fast, have lower internal resistance and vice versa. Viscosity can be defined as the property of a fluid by virtue of which it opposes the relative motion between two surfaces of the fluid that are moving at different velocities or in simple terms, viscosity means friction between the molecules of fluid or opposition to flow. The driving forces behind the origin of surface tension are cohesive and adhesive forces. (Surface tension tries to acquire the minimum surface area of the liquid). Especially it keeps a hurdle between foreign materials and liquid as well as this is the force that holds the liquid molecules bound together.Īnother example, The drops of a liquid are spherical because, for a given volume, a sphere has a minimum surface area. Also, surface tension is also the fundamental property of the liquid surface that holds out against force. Surface tension releases the energy required to increase the surface of the liquid by unit area. The most common example we can observe in our daily life is when we add soap to the water, its surface tension decreases, thereby the liquid with soap mixes easily with dirt on hand and cleans it. Increasing the temperature lowers the net force of attraction between the molecules and decreases surface tension. While other organic liquids, such as benzene and alcohols have lower surface tensions, whereas mercury has higher surface tension. Water has a surface tension of 0.07275 joules per square meter at 20 ☌. It is often expressed as an amount of force exerted on the surface perpendicular to a line of unit length. Surface tension is expressed in energy (joules) per unit area (square meters). The energy required for surface tension is equal to the work or energy required to remove the surface layer of the molecules in a unit area. Surface tension does not depend on the forces of attraction between the particles only but also depends on the forces of attraction of solid, liquid, or gas in close contact with it. So, the net force of attraction acting on the molecule is zero. The molecule lying inside the liquid surface is surrounded by other molecules and is attracted equally in all directions. This property of liquid is based on the fact that the molecules of the liquid at the surface level are in a different situation than those in the interior of the liquid. Surface tension is defined as the tendency of a fluid to shrink into the minimum possible surface area. The viscosity of a fluid is a measure of how sticky the fluid is, on the other hand, Surface tension is the elastic property of a fluid which makes it acquire the least surface area possible. Both of them are dependent on molecular interactions. In this topic, we will learn about two Mechanical Properties of Fluids which are Viscosity and Surface Tension. Liquids and Gases can flow easily and are termed as fluids. Surface tension is determined by the difference in interactions between liquid molecules with the molecules of the liquid in contact.Ī fluid is a substance that has no fixed shape. Viscosity occurs because of an alliance between identical molecules located in the same liquid material. Surface tension Viscosity is dependent on molecular interactions.
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