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Van der Waals force
is a general term for those intermolecular forces that include dipol – dipol and London forces
dipole – dipole force
an attractive intermolecular force resulting from the tendency of polar molecules to align themselves such that the positive end of one molecule is near the negative end of another
London forces (dispersion forces)
the weak attractive forces between the molecules resulting from the small, instantaneous dipoles that occure because of the varying positions of the electrons during their motion around nuclei (resonance of e- cloud, transitional deformation of electron cloud when colliding)
Hydrogene bonding
is a weak to moderate attractive force that exists between a hydrogene atom covalently bonded to a very electronegative atom, and a lone pair of electrons of another small, electronegative atom
Diffusion
the phenomenon, when two or more compounds form a homogenous mixture by the disorganised motion and collisions of the particles
Graham
the speed of the diffusion of the gases is inversely proportional with the square root of the density and molar mass
Melting and freezing point
the temperature, where the vapour pressure of the solid and the liquid form of the compound equals (0,1 MPa = 101,3 kPa = 1 atm) at atmospheric pressure
Boiling point
the temperature, where the pressure of saturated vapour of a liquid reaches the atmospheric pressure (0,1 MPa = 101,3 kPa = 1 atm)
Viscosity (internal friction of liquids)
proportional with the shear force, that removes two unit surfaced liquid layer to a unit distance with a unit speed
Surface tension
proportional with the energy that is necessary the increase the surface of the liquid with a unit
Vapour pressure (tension)
saturated equilibrium vapor pressure in the space above the evaporating liquid. The vapour pressures of the liquids increase exponentially – dependently from the matter – with the increase of the temperature
Distillation
the process when a liquid is evaporated on its boiling point, and its vapour condensates
Liquid crystall
they form a transition from the liquids towards the crystalline compounds; they are liquids but own direction dependent physical properties→ digital displays; monitors; cell membrane (lipid double layer→ liquid – mosaic model)
Unit cell
the smallest unit of a lattice, its periodic repetition forms the crystaline lattice
Isomorphism
different compounds can be characterised with the same lattice structure
Polymorphism
at chemical elements – allotropy: the same compound can form different crystalline lattice