Transcript amorphous solid

13/14 Semester 2
Physical Chemistry I
(TKK-2246)
Instructor: Rama Oktavian
Email: [email protected]
Office Hr.: M.13-15, Tu. 13-15, W. 13-15, Th. 13-15, F. 09-11
Outlines
1. Condensed Phase
2. Properties of liquids
3. Thermal compression and
4. Thermal compressibility and
Vapor pressure
Condensed Phase
The definition of “condensed”
1. reduced in volume, area, length, or scope; shortened: a
condensed version of the book.
2. made denser, especially reduced from a gaseous to a liquid
state.
3. thickened by distillation or evaporation; concentrated:
condensed lemon juice.
http://dictionary.reference.com/browse/condensed
Condensed Phase
The definition of “condensed phase”
Solid and Liquid are condensed phase because the particles are
very close together.
There are strong intermolecular forces
Condensed Phase
The definition of “condensed phase”
made denser, especially reduced from a gaseous to a liquid state.
Liquid state
Structure of liquids
Liquid state
Structure of liquids
Substances that can flow are referred as fluids. Both gases and liquids are fluid
Liquid state
Structure of liquids
•The particles that form a liquid are relatively close together, but not as close
together as the particles in the corresponding solid.
•The particles in a liquid have more kinetic energy than the particles in the
corresponding solid.
•As a result, the particles in a liquid move faster in terms of vibration, rotation, and
translation.
•Because they are moving faster, the particles in the liquid occupy more space, and
the liquid is less dense than the corresponding solid.
Liquid properties
intermolecular forces will play a major role in explaining their physical properties.
Thermal expansion
Compressibility
Vapor pressure
Liquid properties
How to describe P-V-T relationship in liquid state?
The dependence of the volume of a solid or liquid on temperature at constant
pressure can be expressed by
V  V0 1  t 
where :
α is coefficient of thermal expansion
V0 is volume of liquid at 0 C
t is temperatur in Celcius
Liquid properties
How to describe P-V-T relationship in liquid state?
V0 is function of pressure and expressed as
V0  V 1    p 1
0
0
where :
V00 is volume of liquid at 0 C and 1 atm
V0 is volume of liquid at 0 C
 is coefficient of compressibility
Liquid properties
General definition of

and

Equation of state for liquid
V = V(p,T)
Take the partial derivative
 V 
 V 
 dp
dV  
 dT  
 T  p
 p T
Liquid properties
General definition of
1  V 
  
V  T  p
1  V 

V  P T
  

and

Volume expansivity
Isothermal compressibility
 V 
 V 
 dp
dV  
 dT  
 T  p
 p T
EoS for liquid can be written as:
dV
 dT  dp
V
Liquid properties
General definition of
1  V 
  
V  T  p
1  V 

V  P T
  

and

Volume expansivity
The value is usually small
Isothermal compressibility
Liquid properties
General definition of

and

Liquid properties
The effect of pressure change to volume change of liquids
V0  V 1    p 1
0
0
5
If we take   10 atm-1 , then for a pressure of two atmospheres, the volume
of the condensed phase is
The decrease in volume in going from 1 atm to 2 atm pressure is 0.001 %
Liquid is incompressible fluid
Liquid properties
EoS for liquids
dV
 dT  dp
V
Find the volume change when acetone is changed from 293.15 K and 1 bar to
273.15 K and 10 bar
Liquid properties
Other properties of liquid
Viscosity
Surface tension
Vapor pressure
Liquid properties
Viscosity
the resistance of a liquid to flow
Intensive property of liquids
Viscosity depends on:
- The attractive forces between molecules
- Temperature - The viscosity of liquids decreases with increase the temperature
Liquid properties
Effect of temperature
M.A. Mehrabian, M. Khoramabadi, (2007) "Application of numerical methods to study the effect of variable fluid viscosity on the
performance of plate heat exchangers", International Journal of Numerical Methods for Heat & Fluid Flow, Vol. 17 Iss: 1, pp.94 107
Liquid properties
Surface tension
the amount of energy required to increase the surface area of a liquid by a unit
amount
Stronger intermolecular forces cause higher surface tension
Water has a high surface tension (Hbonding)
Liquid properties
Surface tension
Liquid properties
Phase change
Liquid properties
Phase change
Energy Changes Accompanying Phase Changes
• melting or fusion:ΔHfus> 0 (endothermic)
• vaporization:ΔHvap> 0 (endothermic)
• sublimation:ΔHsub> 0 (endothermic).
ΔHdep < 0 (exo). •condensation: ΔHcon < 0 (exo).
• freezing: ΔHfre < 0 (exo).
•deposition:
•The following sequence is endothermic: heat solid → melt → heat liquid → boil →
heat gas
•The
following sequence is exothermic: cool gas → condense → cool liquid →
freeze → cool solid
Liquid properties
Heating curve
Liquid properties
Vapor pressure
the pressure exerted by its vapor when the liquid and vapor are in dynamic
equilibrium
Dynamic equilibrium is a condition in which two opposing processes occur
simultaneously at equal rates
Some of the molecules on the surface of a liquid
have enough energy to escape the attraction of the
bulk liquid.
•These molecules move into the gas phase.
As the number of molecules in the gas phase
increases, some of the gas phase molecules strike
the surface and
return to the liquid.
Liquid properties
Vapor pressure as function of temperature
Liquid properties
Evaporation vs boiling
evaporation is a surface phenomenon - some molecules have enough kinetic energy
to escape
Boling point is the temperature at which the vapor pressure is equal to the external
pressure, bubbles form
Liquid properties
Normal boiling point
The temperature at which the vapor pressure is equal to 1 atm
Solids
Crystalline solid
the units that make up the solid are arranged in a very regular, repeating pattern.
Amorphous solid
An amorphous solid lacks the long range order of a crystalline solid.
Most plastics are amorphous solids. (they are polymers)
Solids
Covalent Network Solids
In a covalent network solid, all of the atoms in a crystal are held together by
covalent bonds.
Some examples of covalent network solids are diamond (C), boron nitride (BN), and
silicon dioxide (SiO2).
Solids
Ionic Solids
An ionic solid consists of oppositely charged ions, held together by strong
electrostatic interactions.
Binary compounds made up of a metal and a nonmetal are in this category.
Example: NaCl
Problems
EoS of liquids
Express the volume expansivity and theisothermal compressibility as functions of
density p and its partial derivatives
For water at 323.15 K (50°C) and 1 bar, K = 44.18 x10-6 bar-1. To what pressure must
water be compressed at 323.15 K (50°C) to change its density by 1 %? Assume that K
is independent of P.
Problems
Castellan prob 5.7