Consider following statements: A. Surface tension arises due to extra energy of the molecules at the interior as compared to the molecules at the surface, of a liquid. B. As the temperature of liquid rises, the coefficient of viscosity increases. C. As the temperature of gas increases, the coefficient of viscosity increases D. The onset of turbulence is determined by Reynold's number. E. In a steady flow two stream lines never intersect. Choose the correct answer from the options given below:

Let us analyze each statement about fluid properties.

Statement A: Surface tension arises due to extra energy of molecules at the interior compared to molecules at the surface.

This is INCORRECT. Surface tension arises because molecules at the surface have higher potential energy than those in the interior (not the other way around). Interior molecules are surrounded by neighbors on all sides and are in a lower energy state.

Statement B: As temperature of liquid rises, the coefficient of viscosity increases.

This is INCORRECT. For liquids, viscosity decreases with increasing temperature because higher thermal energy helps molecules overcome intermolecular forces more easily.

Statement C: As temperature of gas increases, the coefficient of viscosity increases.

This is CORRECT. For gases, viscosity increases with temperature. This is because viscosity in gases arises from momentum transfer between molecular layers, and higher temperature means greater molecular speeds and more momentum transfer. The relationship is $$\eta \propto \sqrt{T}$$.

Statement D: The onset of turbulence is determined by Reynolds number.

This is CORRECT. The Reynolds number $$Re = \frac{\rho v d}{\eta}$$ determines whether flow is laminar or turbulent. Turbulence sets in when $$Re$$ exceeds a critical value.

Statement E: In steady flow, two streamlines never intersect.

This is CORRECT. If streamlines intersected, a fluid element at the intersection would have two velocity directions simultaneously, which is impossible in steady flow.

The correct statements are C, D, and E. The answer is Option A) C, D, E Only.