Q.Write a short note on - a. Vapour pressure. b. Surface tension c. Viscosity.

Step 1 (a). Vapour pressure. Molecules at a liquid's surface constantly escape into the space above as vapour (evaporation); in a closed container, the reverse process (condensation) also occurs, and equilibrium is reached when the rates of evaporation and condensation are equal. The pressure exerted by the vapour at this equilibrium is the liquid's (saturated) vapour pressure -- higher for more volatile liquids with weaker intermolecular forces, and rising with temperature; for water it is specifically called Aqueous Tension.

Step 2 (b). Surface tension. Molecules deep within a liquid are pulled equally in all directions by their neighbours (net force zero), but molecules at the surface have no neighbours above them, so they feel a net inward pull toward the liquid's interior. This makes the surface behave like a stretched membrane that tries to minimise its own area, defined quantitatively as the force acting per unit length along a line on the surface (SI unit N m-1, symbol gamma). It falls with rising temperature and underlies phenomena such as capillary rise, spherical liquid drops, and the cleaning action of soaps. …

Give a short, self-contained note on each of the three named liquid-state properties, covering definition, ph …

• Confusing surface tension (a force-per-length property of the surface) with viscosity (an internal-friction property of the whole flowing liquid). …