Chapter IV review: tests and summary
In a liquid the surface tension force is F = σl and the surface energy W = σS; a wetting liquid rises in a capillary to a height h = 2σ/(ρgr). Solids are crystalline (ordered lattice, definite melting point, anisotropy in monocrystals) or amorphous (disordered, isotropic, soften gradually). In deformation ε = Δl/l₀, σ = F/S and Hooke’s law σ = E|ε| hold. During melting of a crystal and solidification of a liquid the temperature stays constant: Q = λm; evaporation at the boiling point needs Q = rm, and for water λ ≈ 3.36·10⁵ and r = 2.3·10⁶ J/kg. Evaporation cools, saturated vapour is in dynamic equilibrium with its liquid, and the boiling point depends on pressure. The relative humidity of air is φ = ρ/ρ₀·100 % = p/p₀·100 %, the dew point is the temperature at which vapour becomes saturated, and a psychrometer gives φ from the difference of two thermometers.
Make a review map: draw four sections on a page (liquid, solid, change of state, humidity) and write 3 formulas or rules and 1 everyday example in each. Quiz each other with a friend.