Ch 12 - Liquids and Solids

intermolecular forces

forces between two molecules

types of IMF?

• ion-dipole attractions

• ion-ion attractions

• hydrogen bonds

• dipole-dipole attractions

ion-dipole attraction

form between ions and polar molecules solution

ion-ion attractions

strongest IMF, between two ions, lattice structure

hydrogen bonds

particularly strong type of dipole-dipole attraction

dipole-dipole attractions

occurs between all molecules, most notable between nonpolar molecules

What determines melting and boiling points?

IMF

What are the two components of the hydrogen bond?

1. hydrogen bond donor - molecule containing a partially positive H atom bonded to O, N, or F

2. hydrogen bond acceptor - molecule containing partially negative O, N, or F with lone pair electrons

dispersion (London) forces

instantaneous dipole-dipole induced attractions), may last only for a minute, weak, exhibited by all atoms and molecules, with larger atoms and molecules exhibiting moren

IMF from strongest to weakest?

• ion-ion

• ion-dipole

• hydrogen

• dipole-dipole

• dispersion

properties of liquid

• particles are in contact, but not as close as solids

• particles are in constant motion and interact via IMF (weak and temporary)

• weak forces give viscosity, surface tension, and capillary action

viscosity

the resistance to flow determined by the strength of IMF and temp

What happens to viscosity as temp increase?

KE increase and viscosity decreases

surface tension

the tendency of a liquid to minimize its surface

capillary action

the ability of a liquid to flow against gravity up a narrow tube because of adhesion

concave meniscus

formed when a liquid has a high surface tension and cohesions (water)

convex meniscus

formed when a liquid has a high surface tension but no cohesion (mercury)

sublimation

solids directly to a gas

deposition

gas directly to a solid

What does every liquid have?

vapor pressure that is dependent of volume and increases as temp increase, (not linear and a natural log graph is used to plot

clausius-clapeeyron equation

useful for a two point equation

• 2 pressures

• 2 temps

• ln(P₂/P₁) = delta H_vap/R [1/T₁ - 1/T₂]

critical point

vapor and liquid phases are the same

triple point

all 3 phases are present at the same temp and pressure

critical temp

the temperature at which a liquid phase is no longer possible

critical pressure

the vapor pressure at the critical temp

super critical point

beyond the critical point, kind of gas and kind of liquid, different from normal phases

crystalline solids

definite melting points, abruptly forming a liquid once the melting point is reached, highly ordered, sharp melting point

amorphous solids

get softer as their temp is raised, gradually forming a liquid, less ordered, broader melting point

strong solids have?

strong forces

molecular solids

have molecules held to each other by IMF and have low melting points (CO2 and H2O)

ion solids

composed of ions held together by ionic bonds, high melting points (NaCl and MgO)

covalent network solids

composed of atoms connected by covalent bonds, extremely high melting point

metallic solids

composed of metal ions loosely held together by their VE, have a broad range of melting points

types of solids

• network covalent

• ionic solids

• metals

network covalent solid properties

• one big molecule, all atoms connected by covalent bonds

• melting points above 1000 C

• insoluble in common solvents

• poor electrical conductors

• ex: diamond

ionic solid properties

• high melting point (600C - 2000C)

• don’t conduct electricity because of fixed ion position

• often soluble in water or other solvents

• ex: K2Cr2O7

metal properties

• high electrical conductivity

• high thermal conductivity

• ductility and malleability

• insoluble in H2o and common solvents

  • soluble in strong acids

cubic system

• how atoms stack

• unit cell → lattice → space-filling unit cell

simple cubic unit cell

• atoms/unit cell 1:

• packing efficiency: 52%

• coordination number: 6

• radius: l = 2r

body centered cubic unit cell

• atoms/unit cell: 2

• packing efficiency: 68%

• coordination number: 8

• radius: l = 4r/3^1/2

face-centered cubic-unit cell

• atoms/unit cell: 4

• packing efficiency: 74%

• coordination number: 12

• radius: l = 8^1/2 x r