ANS:C - both 'a '& 'b'

Viscosity is a measure of a fluid's resistance to flow. It quantifies how easily a fluid can deform or flow under an applied force. Here's a more detailed explanation:

1. Resistance to Flow: Viscosity is essentially a measure of internal friction within a fluid. When a force is applied to a fluid, such as stirring or pumping, the fluid resists this deformation. The resistance encountered by the fluid as it flows is termed viscosity.
2. Factors Affecting Viscosity:
   • Temperature: Generally, as temperature increases, viscosity decreases. This is because higher temperatures increase the kinetic energy of molecules, reducing the attractive forces between them and making them move more freely, thus reducing viscosity.
   • Pressure: The effect of pressure on viscosity depends on the type of fluid. For gases, increased pressure tends to decrease viscosity, while for liquids, it often increases viscosity.
   • Concentration: In solutions, the viscosity can change with the concentration of solute particles. In concentrated solutions, especially those with large molecules or high molecular weight, the viscosity tends to increase due to increased intermolecular interactions.
3. Importance in Diffusion: In the context of diffusion, viscosity plays a crucial role. Higher viscosity fluids impede molecular diffusion more effectively than lower viscosity fluids. This is because the molecules in a high-viscosity fluid experience greater resistance to movement, making it more difficult for them to diffuse through the fluid.
4. Measurement: Viscosity is typically measured using various techniques, including viscometers. The unit of viscosity depends on the measurement system used; common units include Pascal-seconds (Pa·s), centipoise (cP), and poise (P).
5. Applications: Viscosity is a critical property in numerous industrial processes and applications. For example, in chemical engineering, knowledge of fluid viscosity is essential for designing pumps, pipes, and other equipment. In medicine, viscosity affects blood flow and is important in understanding circulation and cardiovascular health. In food science, viscosity influences the texture and mouthfeel of food products.