Title 1.5 Capillarity, Vapour pressure.pdf ✅

Unit 1 1.5 Capillary, Vapour pressure
Capillarity • is defined as a phenomenon of rise or fall of a liquid surface in a small tube relative to the adjacent general level of liquid when the tube is held vertically in the liquid. • The rise of liquid surface is known as capillary rise while the fall of the liquid surface is known as capillary depression. • It is expressed in terms of cm or mm of liquid. • Its value depends upon the specific weight of the liquid, diameter of the tube and surface tension of the liquid

Expression for Capillary Rise For equilibrium π 4 d 2 x h x ρ x g = σ x πd x cos θ h = σ x πd x cos θ π 4 d 2 x ρ x g = 4σ cos θ ρ gd The value of θ between water and clean glass tube is approximately equal to zero and hence cos θ = 1 , then h = 4σ ρ gd