Thermal chemistry is study of the transfer of heat in
chemical reactions and physical changes.
Student will learn:
1. to read Phase diagrams
2. math calculations of energy for melting,
freezing, vaporization, condensing or
raising temperature of a compound or
element.
3. how to read heating cooling curves
Thermal Chemistry
Phase: any part of a system that has
uniform composition and properties. ( solid, liquid,
gas)
Overhead
Fluid: gas or liquid: a substance that can flow and
take shape of the container.
Diffuse: ability to mix with other liquids or gases (p.364 food
coloring, perfume)
Vaporization: process - liquid or solid changes into a gas.
“you have added energy and vaporized it”
Evaporization: process - particles escape from the surface
of a non boiling liquid and become gas. “naturally evaporated”
Volatile liquids: liquids that evaporate readily “finger nail polish remover”
Condensation: process which a gas becomes a liquid
“ rain, water drops on out side of glass of cold drink”
Boiling: conversion of a liquid to a gas
within the liquid as well as the surface.
Boiling Point: Temperature which vapor pressure of the liquid
equals the atmospheric pressure.
Freezing or solidification: physical change of liquid to a solid
by removal of heat or energy
Freezing Point: Temperature which liquid and solid have
same average kinetic energy.
Melting: physical change of a solid to a liquid
by the addition of energy.
Melting point: the temperature at which a
solid becomes a liquid.
Sublimation: change of a solid directly to a gas.
“CO2.. Dry ice, Iodine, frost free freezer”
Deposition: change of a gas directly to a solid.
“ frost on grass or car windshield ”
Phase Diagrams
graph which shows conditions of phase changes
Triple point
= solid, liquid, gas coexist at equilibrium.
Critical Temperature point =
cannot exist as a liquid regardless of pressure.
o
The critical temperature point of water is 373.99 c. Above this
temperature, water cannot be liquefied, no matter how much
pressure is applied.
Critical Pressure point = lowest pressure at which the
substance can exist as liquid @ critical temp.
The lowest pressure at which water can exist as a liquid is
217.75 atm @ the critical temperature point.
Phase Diagram
Describe all phase changes that would occur when heating the chemical
from -80o to 20o at a constant pressure of 10atm.
At room temperature what is the phase of this chemical?
Phase Diagram
What are the phase changes at 16atm from -100o to 40o and their
corresponding temperatures?
At room temperature what is the phase of this chemical?
Phase Diagram
Given a sample of this chemical, how would you phase change the liquid
into a gas without changing the temperature?
Where is the triple point?
Where is the critical point?
Thermal Chemistry
study of transfer of heat in chemical reactions and
physical changes.
What is the difference?
Temperature
Heat
Thermal energy
Temperature: measurement of motion…
measurement of kinetic energy of the molecules
…. Wood…
…. cold (vs) hot water
……. Fever of 105
Normally use a thermometer
Heat: The transfer of thermal energy. The energy that ‘flows’
from higher Temperature to lower temperature.
… standing beside the burning wood and feeling the warmth…
Thermal energy = total energy of matter…
measured in joules…
Q = thermal energy
Heat of Fusion: energy required to melt solid to a liquid
Q = m Hf
Q = energy
M = mass
Hf = heat of fusion
Heat of Vaporization: energy required to vaporize a liquid
Q = m Hv
Q = energy
m = mass
Hv = heat of vapor
1.
Calculate the amount of energy required to melt a small
ice cube weighing 24 grams.
2. Calculate the amount of energy required to produce
steam from 100 mL of water.
3. Find the molar heat of vaporization for a substance, given
that 4.22 mol of the substance absorbs 32.8 kJ of energy
when it changes from a liquid to a gas.
4. Aluminum is used in manufacturing Pepsi-cola cans.
How much heat energy does the factory need to provide to
melt the 3 grams of aluminum needed per can? The
factory produces 3,000 cans per hour. How much energy
is needed per hour? Aluminum’s melting point is 660
degrees Celsius.
5. Copper is vaporized so it may be infused onto a
fabric for hospital use in fighting germs. Calculate
the energy required for processing 5 grams of
Copper. Copper melting point is 1083 degrees.
6. Zinc is used in making brass. Zinc melts at 420
degrees celsius. Calculate the energy needed to
melt 150kg of Zinc.
7. The molar heat of vaporization of carbon disulfide is
28.4 KJ/mol at its normal boiling point of 45oC. How
much energy is required to vaporize 12 grams of CS2 ?
8. Twenty three thousand two hundred an twenty
nine Joules of energy was used to melt 85 grams of
an unknown metal. Calculate its heat of fusion and
determine if the metal was iron or lead or platinum.
9. The heat of fusion of a metal is 7.35 J/g at its
freezing point of -39oC. Calculate the amount in grams
of this solid metal that can be melted if 5500 J of
energy are available.
10. Turning mercury into a vapor is not easy. But for
some reason your evil boss wants it done. You are
beginning to think he has diabolic plans to eliminate
the employees. How much energy will be needed to
accomplish this for 5 grams of mercury?
Thermal chemistry is study of the transfer of heat in
chemical reactions and physical changes.
Student will learn:
1. Heat of Fusion math calculations
of energy for melting or
freezing a substance.
2. Heat of Vaporization math
calculations of energy for
vaporizing or condensing a
substance.
Calculate the energy required to turn 45mL of
water into steam. Answer in Kj
0
of
30
Thermal chemistry is study of the transfer of heat in
chemical reactions and physical changes.
Student will learn:
1. math calculations of energy condensing or
raising temperature of a compound or
element.
Q = m Cp
t
Substanc
e
Specific Heat
J/gOC
Aluminum
0.897
Copper
0.385
Gold
0.129
Iron
0.449
Lead
0.129
Magnesium 1.023
Mercury
0.140
Nickel
0.444
Titanium
0.523
Zinc
0.388
Water gas
2.02
Water
liquid
4.18
Water solid
2.05
Specific Heat = amount of energy required to raise 1gram of
substance by 1 degree
Q = m Cp
t
Which requires the most heat to heat up?
iron pipe or lead pipe
Which requires least amount of heat to heat up?
magnesium or gold
Which requires least amount of heat to heat up?
Fe, Zn, Ti
WS17.2
1.
How much heat is needed to raise the
temperature of a 20g aluminum Pepsi-cola
can 35 degrees?
2.
Calculate the heat lost from a 5g copper
o
o
penny if cooled from 25 c to 3 c in the
freezer.
3.
Calculate the mass of water that uses
2508J of energy in raising its
temperature from 80oC to 100oC.
4.
Calculate the temperature rise if
224.25J of heat energy was added to a
30gram ice cube.
5. How much energy is needed to raise the
temperature of a gold necklace with a mass
83.0g from 15oC to 39oC?
6. If 66kj of heat energy is absorbed by 9.0kg
of nickel that has an initial temperature of
25oC, what will be the final temperature
after heating?
7. Calculate the specific heat of this
unknown metal that absorbed 450.J of
energy, weighed 10 grams, and the
temperature increased 100oC. Identify
this metal.
8. How much energy is needed to raise the
temperature 30 degrees of 908.0 kg (2
tons) of Zinc?
9. Calculate the amount of energy to be
extracted to cool down a 2 ton solid iron
turbine engine from 150oC to 80oC.
10. Calculate how much more energy it would
take to increase 150oC steam to 400oC
steam having a mass of 200grams.
Thermal chemistry is study of the transfer of heat in
chemical reactions and physical changes.
Student will learn:
1. math calculations of energy condensing or
raising temperature of a compound or
element.
Q = m Cp
t
Ws. 17.3
3.5Kj of heat are added to a 28.2 gram sample
of Fe @20oC. Calculate final Temperature of
the FE.
0
of
30
*
HEATING CURVES
VS
COOLING CURVES
HANDOUT CURVE SHEET
Thermal chemistry is study of the transfer of heat in
chemical reactions and physical changes.
Student will learn:
1. how to read heating cooling curves
Label :
60oc
50oc
40oc
30oc
20oc
10oc
0c
-10oc
-20oc
-30oc
0 kj
25 kj
50 kj
75 kj
100kj
125kj
150kj
175kj
200kj
225kj
Heating-Cooling curve ( Enthalpy of Fusion and Vaporization
250kj
Theory pt.1: The quantity of heat absorbed to melt a solid = the
quantity of heat released to solidify the liquid.
60oc
50oc
40oc
30oc
20oc
10oc
0c
-10oc
-20oc
-30oc
0 kj
25 kj
50 kj
75 kj
100kj
125kj
150kj
175kj
200kj
225kj
250kj
Theory pt.2: The quantity of heat absorbed to vaporize a liquid =
the quantity of heat released to condensate the vapor.
60oc
50oc
40oc
30oc
20oc
10oc
0c
-10oc
-20oc
-30oc
0 kj
25 kj
50 kj
75 kj
100kj
125kj
150kj
175kj
200kj
225kj
250kj
Theory pt.3: All solids absorb heat as they melt . This causes a
phase change rather than a temperature change.
60oc
50oc
40oc
30oc
20oc
10oc
0c
-10oc
-20oc
-30oc
0 kj
25 kj
50 kj
75 kj
100kj
125kj
150kj
175kj
200kj
225kj
250kj
Ex) ice melting: Temperature remains constant until all ice has melted…..
The temperature of water will increase only after all ice has melted.
Ex) boiling water.
1. Which segments on the curve represent constant temperature?
2. What is the boiling point of this substance?
3. How much energy is needed for vaporization?
4. If this chart is based on 2 grams of substance how much energy is
needed to melt 10 grams of the substance.
60oc
50oc
40oc
30oc
20oc
10oc
0c
-10oc
-20oc
-30oc
0 kj
25 kj
50 kj
75 kj
100kj
125kj
150kj
175kj
200kj
225kj
250kj
1. What temperatures do phase changes occur?
2. Which portion represents an decrease in heat absorbed while
kinetic energy remains constant?
3. What is the quantity of the Heat of Vaporization?
4. What temperature is condensation?
TIME
2
4
6
8
10
12
14
16
18
20
22
24
26
28
29
30
32
34
36
TEMPERATURE
25
30
35
40
45
45
45
45
50
55
60
65
70
75
75
75
75
80
85
What is the melting
Temperature?
How many minutes does
this take to melt?
What is the boiling
point?
Ws. 17.4
Use the chart above to complete the following essay
At the start of the experiment, point A and point B the substance is a
___________________. Its melting point in degrees is ______________.
It takes ________ minutes for this substance to melt. Point D is called the
Heat of Fusion. The mathematical formula for point D is
_________________. Point D is a phase change. The
____________________stays constant during a phase change. The
temperature begins to rise during the liquid phase for ______ minutes. The
boiling temperature for this substance is _______. It takes
_________minutes and _________ joules of energy to vaporize this
substance from its liquid phase. The math formula for the slant lines at B, F,
and J is ____________________? This substance is a___________ at
point J. At point K the temperature may continue to rise that is one reason
why steam will burn you much quicker than boiling liquids.
When gaseous substances are cooled, energy is released. The cooling
curve will be the opposite of the heating curve. Energy is released as the
substance changes phases from _______ to _______________ and
again when it changes from ____________ to __________________.
Segments _____ and _____ on the cooling curve represent fix points on
a thermometer.
If the chart above is based on 4 grams of Gold, how much
energy does it take to melt 12 grams of Gold? ___________. How long
would it take to melt 4 grams? _____________. How long it would it
probably take to melt 12 grams? ________________________.
When water freezes,
each gram loses an amount of heat equal to its heat of
1.
2.
3.
4.
5.
6.
Vaporization
Sublimation
Reaction
Melting point
Freezing point
Fusion
The phase change represented by the following
reaction is…
I2(s)
I2(g)
1.
2.
3.
4.
Sublimation
Condensation
Melting
boiling
Thermal chemistry is study of the transfer of heat in
chemical reactions and physical changes.
Student will learn:
1. how to read heating cooling curves