The boiling point at pressure 1 atm is known as normal boiling point. Normal boiling point is slightly greater than the standard boiling point as molecules change into the vapor phase and density of vapor increases.

As there is a rise in temperature the viscosity of liquid increases while the viscosity of gas decreases. In liquids, due to rise in temperature, molecules have high thermal energy so the can overcome intermolecular attractions.

The type of flow in liquids when each path flows in a different path, that do not interfere with each other is laminar flow. At any point in the fluid, the velocity of a fluid is constant is a characteristic of laminar flow.

Surface Tension is the tendency of a fluid to occupy least surface area as possible. It is defined as the force per unit distance. So, the units of surface tension are Newton/meter in S.I. the system, Dyne/cm in C.G.S system.

The formula of force required to maintain the flow of layers is given by the formula F = ηAdu/dz, where η is the coefficient of viscosity, A is the area of contact and du/dz is the velocity gradient. So by substituting we get an answer as 0.25dz/du.