IMF

SOLID vs LIQUID vs GAS



  • Solids and liquids are collectively referred to as condensed matter. Characterised by strong IMF, which maintains local order by keeping distances between individual molecules or atoms within close bounds.

  • relatively few substances exist in the gaseous state under typical conditions but gases are very important



Water changes solid to liquid to gas the molecules remain intact. The changes in states are due to changes in the forces among the molecules rather than in those within the molecules.



INTRAMOLECULAR vs INTERMOLECULAR forces



● INTRAMOLECULAR: involve covalent or ionic bonding (occur within molecule)

● INTERMOLECULAR: involve weaker interactions (occur between molecules)



Interparticle forces (forces in ionic and metallic substances)



Types of IMF



1. Dipole-dipole (permanent) = polar

2. Hydrogen bonds = polar w/ H & F/O/N/S

3. van der Waals’ = induced (polar or not but the only IMF in nonpolar)

Ion-dipole

  • Attraction between charge on anion and end of dipole with opposite charge

  • 35-400

Dipole-dipole

  • Attraction between opposite partially chraged ends of polar molecules

  • 5-30

Hydrogen bond

  • Attraction between partially positively charged H atom which attached to highly electronegative atom and a line pair on another atom

  • 10-40

London dispersion

  • Attraction between an instantaneous dipole and a dipole induced in a neighboring atom or molecule

  • <1-40



THE LIQUID STATE



Liquids and liquid solutions are vital to our lives.



Liquids exhibit many characteristics that help us understand their nature: low compressibility, lack of rigidity, and high density compared with gases



VISCOSITY



● measure of liquid’s resistance to flow

● Factors that determine viscosity:

○ Strength of IMF (large IMF tend to be

highly viscous)

○ size/shape of molecule (Molecular

complexity leads to higher viscosity)

○ Temperature (more KE, lower

viscosity)




COHESIVE vs ADHESIVE

  • cohesive forces (IMF among the molecules of the liquid, aims to minimize surface)

  • adhesive forces (IMF between the liquid molecules & the container)

  •  adhesive forces toward the container > its cohesive forces = concave shape of the meniscus, else convex shape water’s adhesive forces toward the glass are stronger than its cohesive forces (“wet surface”)



CAPILLARY ACTION

● spontaneous rising of a liquid in a narrow glass tube (due to cohesive & adhesive force)

● Liquid flow through material because of attraction between the liquid & the material (adhesive + cohesive force >

gravity)



Surface Tension



● the resistance of a liquid to an increase in its surface area (energy required to increase the surface area of a liquid)

● depends on strength of cohesive forces (liquids with relatively large IMF tend to have relatively high surface tensions)

● Water has an irregularly high surface tension (strong H bonds & size)



A molecule in the interior of a liquid is attracted by the molecules surrounding it, whereas a molecule at the surface of a liquid is attracted only by molecules below it and on each side.










Types of Solids:



AMORPHOUS SOLID:

● with considerable disorder in their

structures.

● Disordered, disorganized, random,

no lattice

Ex.  Cotton Candy, glass

CRYSTALLINE SOLIDS:

● highly regular arrangement of their

components

● Ordered, organized, regularly

repeating, has lattice structure

Ex.  Table Salt 



Crystalline solids are dtermined by X-ray diffraction.



Types of Crystalline Solids

  1. Molecular solids

  • Dipole-dipole or LDF

  • Discrete molecules

  1. Ionic Solids

  • Ions

  • Ionic

  1. Metallic solids/ Atomic solids

  • Metal atoms

  • Delocalized covalent

  1. Network

  • Nonmetal atoms

  • Direcctional covalent