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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.

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Presentation on theme: "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."— Presentation transcript:

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

4 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.

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

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

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

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

9 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.

10 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.

11 Heat Added Temperature Rise

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

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

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

15 This melting process is called fusion.

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

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

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

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

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

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

22 This is the boiling point of the liquid.

23 The energy required to cause this transition..

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

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

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

27 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.

28 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.

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

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

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

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

33 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

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

35 Heat of Fusion of Ice

36 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

37 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

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

39 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

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

41 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

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

43 What is

44 Which has the greater? Fe H2OH2O or

45 Specific Heat Capacity - 13 min

46 is used to measure heat change

47 Calorimetry - 13 min

48 Specific Heat of a Metal

49 Lab Burners and BTUs

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52 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.

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54 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

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56 kPa normal atmospheric pressure

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58 TP Triple Point

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60 TbTb Normal boiling point

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62 TmTm Normal melting point

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64 TcTc Critical temperature

65 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

66 Calories in a Peanut

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