E N T H A L P Y - H heat content in matter:

E N T H A L P Y - H heat content in matter: natural systems tend to go from a state of high energy to a state of low energy.

E N T H A L P Y The phases of matter represent "classes" of molecular motion found at different temperatures.

E N T H A L P Y The phases of matter represent "classes" of molecular motion found at different temperatures. X Kinetic Energy

E N T H A L P Y The phases of matter represent "classes" of molecular motion found at different temperatures. X HEAT

E N T H A L P Y q = U + P V q = heat gained or lost U = internal energy P = Pressure V = volume

E N T H A L P Y H fus - heat of fusion As energy is added to a solid at its melting point, ALL the energy is used to increase the kinetic energy of the molecules during the phase change.

E N T H A L P Y H fus - heat of fusion The amount of heat needed to change one gram of a solid into a liquid at its melting point.

Heat Added Temperature Rise

Every phase change is accompanied by a change in the energy of the system.

As the temperature of a solid increases, its particle vibration increases.

When a solid melts, its particles are freed to move with respect to one another.

This melting process is called fusion.

The increased freedom of motion of the molecules or ions comes at a price...

measured by the heat of fusion, or enthalpy of fusion,  H fus

As the temperature of a liquid increases, the molecules move with increasing energy.

When increasing temperature, the concentration of gas-phase molecules just above the surface of the liquid increases.

These gas-phase molecules exert a pressure on the liquid called vapor pressure.

This vapor pressure increases with temperature until it equals the atmospheric pressure.

This is the boiling point of the liquid.

The energy required to cause this transition..

is called the heat of vaporization or enthalpy of vaporization,  H vap

solid/liquid phase change q = m  H fus q = heat gained or lost m = mass  H fus = heat of fusion

E N T H A L P Y H fus H 2 O = 334 J/g H fus lead = J/g

E N T H A L P Y As energy is added to a liquid at its boiling point, ALL the energy is used to increase the kinetic energy of the molecules during the phase change.

E N T H A L P Y H vap - heat of vaporization The amount of heat needed to change one gram of a liquid into a gas at its boiling point.

liquid/gas phase change q = m  H vap q = heat gained or lost m = mass  H vap = heat of vaporization

E N T H A L P Y H vap H 2 O = 2260 J/g

change temp within phase q = m   C p q = heat gained or lost m = mass  = “change in temperature” C p = specific heat capacity

Specific Heat Capacity The heat required to raise the temperature of one gram of a substance by one Celsius degree.

Specific Heat Capacity C p of ice = 2.06 J/g.C o C p of water = 4.18 J/g.C o C p of steam = 2.02 J/g.C o C p of copper =.385 J/g.C o

q=m  H vap - change phase q=m  H FUS - change phase q=m  C p - change temp

Heat of Fusion of Ice

How much heat is needed to convert 250 grams of ice at -30 o C to vapor at 150 o C? 1. Change temp of ice 2. Melt ice 3. Change temp of liquid water 4. Vaporize water 5. Change temp of vapor 6. Add total heat used

Step 1 raise temp of ice q = m  T C p q = (250g) (30 C o ) (2.06 J/g. C o ) q = 15,450 Joules

Step 2 melt ice q = m  H fus q = (250g) (334 J/g) q = 83,500 Joules

Step 3 raise temp of liquid water q = m  T C p q = (250g) (100 C o ) (4.18 J/g. C o ) q = 104,500 Joules

Step 4 vaporize liquid water q = m  H vap q = (250g) (2260 J/g) q = 565,000 Joules

Step 5 raise temp of water vapor q = m  T C p q = (250g) (50 C o ) (2.02 J/g. C o ) q = 25,250 Joules

Step 6 q = 15,450 83, , ,000 25,250 q = 794,000 Joules

What is

Which has the greater? Fe H2OH2O or

Specific Heat Capacity - 13 min

is used to measure heat change

Calorimetry - 13 min

Specific Heat of a Metal

Lab Burners and BTUs

P h a s e D i a g r a m A g r a p h s h o w i n g t h e p h a s e s o f m a t t e r a s t h e y r e l a t e t o t e m p e r a t u r e a n d p r e s s u r e.

M a j o r p o i n t s o n a p h a s e d i a g r a m Normal Atmospheric Pressure Triple point Boiling Point Boiling Point Melting point Melting point Critical temperature Critical temperature

kPa normal atmospheric pressure

TP Triple Point

TbTb Normal boiling point

TmTm Normal melting point

TcTc Critical temperature

V a n d e r W a l l s A t t r a c t i o n T h e f o r c e o f a t t r a c t i o n b e t w e e n m o l e c u l e s m o l e c u l e s

Calories in a Peanut