Key Terms and Concepts
 temperature
 heat
 thermal energy
 kinetic energy
 potential energy
 particle speed
 particle spacing
 phase change
 conduction
 convection
 radiation
 linear expansion
 specific heat capacity
 heat of fusion
 heat of vapourization
 coefficient of linear expansion
Goals
1. Describe how adding/removing energy changes the particles of a substance.
2. Calculate how temperature changes when energy is added/removed from a
sample.
3. Calculate the quantity of energy needed to be added/removed from a sample in
order for a phase change to occur.
4. Calculate the change in length of a solid when energy is added/removed to
change the temperature.
5. Analyze a heating/cooling graph for a sample.
Equations
𝑄 = 𝑚𝑐∆𝑇
𝑄 = 𝑚𝐻𝑓
𝑄 = 𝑚𝐻𝑣
∆𝐿 = 𝛼𝐿𝑖 ∆𝑇
1
PHYSICS 20: Heat: Heat Concepts
1. Heat Vocabulary:
a. Write what you understand each of the following terms means.
b. Use each term in a sentence to demonstrate its meaning.
i. heat:
ii. kinetic energy:
iii. particles (atoms/molecules):
iv. particle speed:
v. particle spacing:
vi. phase change:
vii. temperature:
viii. potential energy:
Create a concept map using the terms on the preceding page.






Start with two terms that you believe have a strong connection.
Put each term into a bubble.
Be sure to explain the connection between the terms.
Continue adding terms and explanations of connections.
You can use Inspiration or Cmap (free at: http://cmap.ihmc.us/) to create a digital version of
your concept map.
Do this on a separate page so that it can be submitted.
2
PHYSICS 20: Heat – Heating H2O Activity
Purpose: to observe the behavior of water as it is heated from a solid until it is
vapourized.
Background:
 Thermometers: the graduations on the thermometer have a scale of 1°C.
o Measurements where the red liquid lines up with a graduation will be
recorded as ##.0°C
o Measurements where the red liquid ends between graduations will be
recorded as ##.5°C
o ALL TEMPERATURES will be recorded to one decimal place!
Procedure:
Part A
1. Set up the apparatus as demonstrated by your teacher
2. Obtain a 250 ml beaker with crushed ice
3. Place the 250 ml beaker of ice in the large beaker (water bath)
4. Record the initial temperature of the ice.
5. Light the Bunsen burner and begin heating the water bath
6. Record the temperature of the ice/water in the 250 ml beaker every 30
seconds
7. Make a note of the time when the ice:
a) begins melting
b) is all melted
8. Once the temperature reaches 50°C turn off the Bunsen burner and stop
heating.
9. Remove the 250 ml beaker from the water bath
Part B:
1. Record the ‘initial’ temperature of the hot water in the water bath
2. Light the Bunsen burner and begin heating the water bath
3. Record the temperature of the water every 30 seconds
4. Make a note of the time when the water:
a) Begins boiling
5. Continue to ear for 5 minutes once the water begins boiling
6. Continue to record the temperature every 30 seconds
7. After 5 minutes of boiling turn off the Bunsen burner
8. Allow the apparatus to cool and clean up
3
Data: the following is an example of the headings for a data table
TIME (min)
Data Set #1:
Temperature (°C)
Data Set #2
Temperature (°C)
0
0.5
1.5
2.0
…
Analysis:
Prepare a graph of Temperature vs Time using your data. Both sets of data can be
plotted on the same graph.
1. Data Set #1 produces a graph with two distinct regions. What is happening to
the water temperature during these two regions?
2. Data Set #2 produces a graph with two distinct regions. What is happening to
the water temperature during these two regions?
3. What do you hypothesis is happening to water molecules during periods when
the temperature does not change significantly? Are the molecules still gaining
energy?
Conclusion: use the RERUN format to assist in writing your conclusion.
R: Recall what you did in the activity to obtain your data.
E: Explain the purpose of the activity.
R: Results – describe the graphs created from your data. Why do you suppose the
graphs show this behavior for water? What connection is there between heating
water molecules and the resulting temperature behavior?
U: Uncertainties – describe any limitations of the procedure or apparatus.
N: New Knowledge – what have you learned? How might this knowledge be used by
people in the ‘real world’?
4
PHYSICS 20: Heat – Measuring Temperature
A Brief History of Temperature Measurement (source: http://en.wikipedia.org/)
In 1701, Ole Christensen Rømer (1644-1710) created one of the first practical
thermometers. Rømer's thermometer used red wine as the temperature indicator.
Rømer created a temperature scale for his thermometer with 0 representing the
temperature of a salt and ice mixture (at about 259 K), 7½ representing the
freezing point of water (273.15 K), and 60 representing the boiling point of water
(373.15 K). (In 1676, Rømer became the first scientist to measure the speed of
light.)
Daniel Gabriel Fahrenheit (1686-1736) devoted most of his life to creating precision
meteorological instruments. Fahrenheit invented the mercury thermometer in 1714,
and later discovered the effect of pressure on the boiling point of liquids.
Fahrenheit sought to create a practical temperature scale in which 0 corresponded
with the coldest temperature normally encountered in Western Europe and 100
corresponded to the hottest temperature. Fahrenheit initially created a
temperature scale in which 0 represented the temperature of a salt and ice mixture (at about 255
K), 30 represented the freezing point of water (273.15 K), and 90 representing the mean human
body temperature (about 310 K). Fahrenheit later adjusted his temperature scale so that 32
represented the freezing point of water and 212 represented the boiling point of water (373.15 K).
The Fahrenheit temperature scale is still used today in the United States and other backward
places.
In 1731, Réne Antoine Ferchault de Réamur (1683-1757) created a simpler
temperature scale in which 0 represented the freezing point of water (273.15 K)
and 80 represented the boiling point (373.15 K). The Réamur temperature scale
became popular in France, but it was superseded by the centigrade temperature
scale.
In 1742, Anders Celsius (1701-1744) created an inverted centigrade temperature
scale in which 0 represented the boiling point of water (373.15 K) and 100
represented the freezing point (273.15 K).
In 1744, Carl Linnaeus (1707-1778) suggested reversing the temperature scale of
Anders Celsius so that 0 represented the freezing point of water (273.15 K) and
100 represented the boiling point (373.15 K). The centigrade relative temperature
scale gradually became popular throughout the world. The units of the centigrade
temperature scale were designated "degree centigrade" (symbol °C).
5
In 1848, William Thomson (1824-1907) proposed a thermodynamic temperature
scale which assigned 0 to thermodynamic absolute zero and used the degree
centigrade as its base unit. This absolute scale was later named the Kelvin
thermodynamic temperature scale (after Thomson's peer title: Lord Kelvin) and its
unit designated degree Kelvin (symbol ºK).
In 1859, William John Macquorn Rankine (1820-1872) proposed another
thermodynamic temperature scale which also assigned 0 to thermodynamic absolute
zero, but used the degree Fahrenheit as its base unit. This absolute scale was later
named the Rankine thermodynamic temperature scale and its unit designated
degree Rankine (symbol °R).



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
In 1948, the Ninth General Conference on Weights and Measures changed the name "degree
centigrade" to "degree Celsius" (symbol °C) in honor of Anders Celsius.
In 1954, the Tenth General Conference on Weights and Measures selected the degree Kelvin as
the metric unit of thermodynamic temperature. The degree Kelvin was named in honor of its
creator, Sir William Thomson, Baron Kelvin of Largs, Lord Kelvin of Scotland.
The conference defined the degree Kelvin by assigning the exact value 273.16°K to the triple
point of water. The triple point of a substance is the thermodynamic singularity at which the
gas, liquid, and solid phases may coexist in thermodynamic equilibrium. A triple point is
therefore a much more accurate temperature reference than either a freezing point or a
boiling point.
In 1967, the Thirteenth General Conference on Weights and Measures changed the name of the
thermodynamic temperature unit degree Kelvin (symbol °K) to merely kelvin (symbol K).
The conference redefined Celsius temperature as the thermodynamic temperature minus
273.15 kelvin. (ºC = K – 273.15)
1. Create a timeline showing the development of measuring temperature. Be sure
to use an appropriate scale for your time axis.
2. If you had a thermometer which had no markings, how would YOU add markings
so that you could use the thermometer to measure air temperatures in degrees
Celcius?
3. How would you add markings so that you could use the thermometer to measure
air temperatures in Kelvin?
4. Why is using the boiling point and freezing point of water better than using
some mixture of salt and ice and water?
6
5. Temperature Conversions: Make the following conversions between degrees
Celcius and Kelvins.
a. Melting temperature of H2O:
ºC =
K
b. Boiling temperature of H2O:
ºC =
K
c. Room temperature (make one up):
ºC =
K
d. Outside temperature on a hot Saskatchewan summer day:
ºC =
K
e. Outside temperature on a cold Saskatchewan winter night:
ºC =
K
f. Temperature at which molecular motion stops (absolute zero – read the
notes!)
ºC =
g. Temperature of liquid nitrogen:
ºC =
K
77
K
h. Melting point of hydrogen:
-259.14 ºC
=
K
i. Melting point of mercury:
-38.72 ºC
=
K
j. Melting point of gold:
ºC = 1337.73
K
Use: Fundamentals of Physics: An Introductory Course – pages 196 to 198
6. What are the main points of the Kinetic-Molecular Theory?
7. According to the kinetic-molecular theory, what is the difference between a
cold glass of water and a hot glass of water?
8. When we measure the temperature of a substance, what are we measuring
about the particles of the substance?
9. What makes up the ‘total thermal energy’ of an object?
7
PHYSICS 20: Transferring Heat Energy – Conduction, Convection, Radiation
Method of
Energy Transfer
CONDUCTION
What It Is
Examples
CONVECTION
RADIATION
8
PHYSICS 20: Heat – Heating Water Activity
PURPOSE:
 To observe the temperature of a system reaching a thermal equilibrium
 To develop a mathematical equation to represent the temperature changes when
mixing hot and cold water.
THEORY:
 When two substances are mixed, energy is transferred from the hotter to the
colder substance. This transfer of energy can occur through conduction,
convection, or radiation.
 When the two substances are the same temperature, this is called the
equilibrium temperature and there is no more transferring of energy.
HYPOTHESIS: use cold water = 10ºC and hot water = 90ºC
 When equal quantities of hot and cold water are mixed the equilibrium
temperature will be:
 When there is more cold water than hot water in a mixture the equilibrium
temperature will be:
 When there is more hot water than cold water in a mixture the equilibrium
temperature will be:
VARIABLES:
 What is the independent variable for this activity?
 What is the dependent variable for this activity?
 What are some of the controlled variables for this activity?
APPARATUS & PROCEDURE:
 Draw and label a sketch of the apparatus used and explain how it was used.
DATA: use the following for headings in a data table.
TRIAL
Cold
Cold Water
Hot water
Hot Water
Water
Initial
Quantity
Initial
Quantity
Temperature
Temperature
(TCi)
(THi)
Equilibrium
Temperature
(Tf)
9
OBSERVATIONS:
 Take note of anything you observe occurring as you prepare the mixture or
while the mixture is reaching thermal equilibrium.
ANALYSIS:
CALCULATIONS: use the following for headings in a
TRIAL Mass of
Mass of


Cold
Hot
Temperature
Temperature
Water
Water
Cold Water
Hot Water
1.
calculation table
(m)(T)
for Cold
Water
(m)(T)
for
Hot
Water
QUESTIONS:
Cold Water:
a) What happened to the temperature of the cold water?
b) What change has occurred in the behavior of the cold water particles?
c) How has the thermal energy of the cold water particles changed?
d) Did the temperature of the cold water change by the same amount in each trial?
1.
Hot Water:
a) What happened to the temperature of the hot water?
b) What change has occurred in the behavior of the hot water particles?
c) How has the thermal energy of the hot water particles changed?
d) Did the temperature of the hot water change by the same amount in each trial?
1.
(m)(T) :
 How are the (m)(T) values similar for the cold water?



How are the (m)(T) values similar for the hot water?
In each trial, how does the (m)(T) product compare between the cold water and the
hot water? Are they similar or very different?
What does the product (m)(T) represent for each quantity of water? (Recall what
happens to each quantity of water curing each trial.)
2. Which of the three methods of energy transfer (conduction, convection, radiation) was mostly
likely occurring in Styrofoam-cup calorimeter? Explain.
CONCLUSION: use the RERUN format to assist in writing your conclusion.
 RECALL: what was the purpose of the activity?




EXPLAIN: what did you do to complete the activity?
RESULTS: How does the initial temperature and mass of water affect the equilibrium
temperature? What equation could be used to represent the effect of mass and initial
temperature on the equilibrium temperature?
UNCERTAINTY: what were sources of experimental ‘error’ or uncertainty?
NEW: what did you learn through this activity and how could this knowledge be used or applied
to real-life situations?
10
PHYSICS 20: Heat – Mixing Water Calculations
When mixing quantities of hot and cold water the following equation can be used:
also:
𝐦𝐜 ∆𝐓𝐜 = −𝐦𝐡 ∆𝐓𝐡
∆𝐓 = 𝐓𝐟 − 𝐓𝐢
so:
𝐦𝐜 (𝐓𝐟 − 𝐓𝐢𝐜 ) = −𝐦𝐡 (𝐓𝐟 − 𝐓𝐢𝐡 )
1. 400 grams of cold water at 10°C is mixed with warm water at 80°C. The final
temperature of the water mixture is 30°C. Calculate the mass of the hot water.
2. 500 grams of cold water is mixed with 700 grams of warm water at 60°C. The
final temperature of the water mixture is 40°C.
a. Calculate the change in temperature of the cold water.
b. Calculate the initial temperature of the cold water.
3. 800 grams of cold water is mixed with warm water. The cold water is initially at
15°C and the warm water is initially at 70°C. The equilibrium temperature of the
mixture is 40°C. Calculate how much warm water was mixed.
4. 800 grams of cold water at 10°C is mixed with 500 grams of hot water at 75°C.
Calculate the equilibrium temperature of the water mixture.
11
PHYSICS 20: Heat – Hot Metal Activity
PURPOSE:
 To observe the temperature of a system reaching a thermal equilibrium
 To develop a mathematical equation to represent the temperature changes when
mixing a hot metal and cold water.
THEORY:
When two substances are mixed, energy is transferred from the hotter to the
colder substance. This transfer of energy can occur through conduction,
convection, or radiation. When the two substances are the same temperature, this
is called the equilibrium temperature and there is no more transferring of energy.
HYPOTHESIS: use cold water = 10ºC and hot metal = 90ºC
 Will mixing two different substance produce an equilibrium temperature that
follows the equation m1 ΔT1 = m2 ΔT2 ?
VARIABLES:
 What is the independent variable for this activity?
 What is the dependent variable for this activity?
 What are some of the controlled variables for this activity?
APPARATUS & PROCEDURE:
 Draw a sketch of the apparatus used and explain how it was used.
DATA:
TRIAL
(metal)
Cold
Water
Mass
Cold Water
Initial
Temperature
(TCi)
Hot metal
Mass
Hot metal
Initial
Temperature
(THi)
Equilibrium
Temperature
(Tf)
12
OBSERVATIONS:
 Take note of anything you observe occurring as you prepare the mixture or
while the mixture is reaching thermal equilibrium.
ANALYSIS:
CALCULATIONS:
TRIAL Mass of

(metal)
Cold
Temperature
Water
Cold Water
Mass of
Hot
Metal

Temperature
Hot Metal
(m)(T)
for Cold
Water
(m)(T)
for
Hot
Metal
Class Results:
Metal
1.
2.
3.
4.
Hot Metal (m)(T)
Cold Water (m)(T)
Class Results
Class
Average
QUESTIONS:
Does the (m)(T) for cold water equal the (m)(T) for the hot metal?
Do the class results and average show a pattern for each metal?
What does the ratio of Hot Metal (m)(T) indicate?
Cold Water (m)(T)
Does the equation we develop for mixing water work with two different
substances? Why might it require some changes?
CONCLUSION: use the RERUN format to assist in writing your conclusion.
 RECALL: what was the purpose of the activity?
 EXPLAIN: what did you do to complete the activity?
 RESULTS: what did you observe about the temperature changes for the water
and metal? Does your math equation still work for this equilibrium?
 UNCERTAINTY: what were sources of experimental ‘error’ or uncertainty?
 NEW: what did you learn through this activity and how could this knowledge be
used or applied to real-life situations?
13
PHYSICS 20: Heat Unit – Energy Change – Practice
 When energy is added to a substance either the temperature changes or the
phase changes.
 Temperature change = change in speed of particles
 Phase change = change in spacing of particles
Temperature Change: The following equation can be used when a temperature
change occurs for a substance:
Q = m c ΔT
Where:
Q = quantity of energy transferred (gained or lost)
m = mass of substance
c = specific heat capacity: amount of energy (in joules) needed to change the
temperature of 1 gram of a substance by 1ºC. Check table of values provided
ΔT = change in temperature = Tf – Ti = final temp – initial temp
Practice Questions:
1. A copper pot has a mass of 750 grams. The pot contains 1.2 kg of vegetable oil.
Both pot and oil are heated from 20ºC to 150 ºC
a. What is the specific heat capacity for copper?
b. What is the specific heat capacity for vegetable oil?
c. Calculate the amount of energy added to the copper pot to achieve the
temperature change from 20ºC to 150ºC.
d. Calculate the amount of energy absorbed by the vegetable oil as it is
heated from 20ºC to 150ºC. Be aware of units!
2. An unknown metal object has a mass of 200 grams. The metal cools from 100ºC
to 20ºC and releases 14500 J of energy.
a. Calculate the specific heat capacity of the unknown metal.
b. Identify the metal using its specific heat capacity.
3. An 800 gram glass bowl absorbs 21250 J of energy.
a. What is the specific heat capacity of glass?
b. Calculate the change in temperature of the glass bowl.
14
4. A hot brass weight is dropped into 500 grams of water. The brass cools from
120ºC to 55ºC. The water heats up from 20ºC to 55ºC.
a. Calculate the amount of energy absorbed by the water.
b. How much energy has the brass weight released?
c. Calculate the mass of the brass weight.
Phase Change: The following equations can be used when a phase change occurs for
a substance
Q = m Hf
or
Q = m Hv
Where:
Q = quantity of energy transferred (gained or lost)
m = mass of substance
Hf = Heat of Fusion: amount of energy (in joules) needed to melt or freeze each
gram of a substance
Hv = Heat of Vaporization: amount of energy (in joules) needed to vaporize or
condense each gram of a substance
Practice Questions:
1. A gold ingot is warmed to its melting temperature of 1064 °C. How much
additional energy must be added to the 250 gram gold ingot in order to melt it?
2. 400 grams of water is collected from a water distiller. The distiller heats
water so that it boils and then collects and cools the steam. How much energy
was removed from the 100 °C steam so that it could condense to liquid water?
3. Before electricity was widely available ice was used to keep food cool in houses
using ‘ice chests’. A block of ice about 20 kg was used weekly in a home ‘icebox’.
The temperature of the ice was about 0C when it was delivered. As it melted,
how much heat did the block of ice absorb?
15
HEAT PROPERTIES OF SUBSTANCES
Material
Aluminum
Brass
Brick
Carbon
Concrete
Copper
Glass (Crown)
Glass (Pyrex)
Gold
Human Body
Ice
Iron
Lead
Marble
Platinum
Pyrex
Silver
Steel
Wood
Zinc
Specific Heat
Capacity Value
Heats of
Fusion
Heats of
Vapourization
c
Hf
Hv
𝑱
( )
𝒈
𝑱
( )
𝒈
𝑱
(
)
𝒈 °𝑪
0.903
0.376
3.00
0.710
2.90
0.385
0.664
0.78
0.130
3.47
2.16
0.460
0.130
0.87
205
5070
63
1640
334
266
20.4
6290
864
Coefficients of
Linear
Expansion
α
(𝟏⁄°𝑪)
25 x 10-6
12 x 10-6
16 x 10-6
9 x 10-6
3 x 10-6
12 x 10-6
9 x 10-6
3 x 10-6
0.235
10.4
2360
12 x 10-6
1.76
0.388
Ethyl alcohol (ethanol)
Methyl alcohol (methanol)
Glycerine
Mercury
Nitrogen (Liquid)
Vegetable oil
Water
2.30
2.50
2.40
0.140
0.110
2.00
4.18
Air
Carbon dioxide
Helium
Hydrogen
Oxygen
Steam
0.995
0.836
5.25
14.40
0.916
2.02
Q = m c ΔT
109
99
855
878
11.5
272
2260
Q = m Hf Q = m Hv
ΔL = α L ΔT
16
PHYSICS 20: HEAT – Temperature Change & Change in Length
When the temperature of a substance changes it results in the change in speed of
the particles of the substance. There is also a small change in the spacing of the
particles. The change is not enough to cause a phase change, only a change in the
length of the object.
The following equation can be used to calculate the change in length of an object
due to a change in temperature:
∆𝑳 = 𝜶 𝑳𝒊 ∆𝑻
Where:
ΔL = change in length = final length – initial length = Lf – Li
α = coefficient of Linear Expansion
Li = initial length of object
ΔT = change in Temperature = final temp – initial temp = Tf – Ti
Practice Questions:
1. A steel cable has a length of 30 metres at a temperature of 10 °C.
a) What is the change in length of the cable when the temperature changes to
30 °C?
b) What is the new length of the steel cable?
2. An aluminum bar has a length of 10 metres when the temperature is 25 °C.
What is the length of the aluminum bar when the temperature is -25 °C?
17
PHYSICS 20: Heat – Homework Assignment
1. 250 grams of water in a glass cup has an initial temperature of 15C. The
cup and water are placed in a microwave oven and heated until the
temperature of the water is 75C.
a. Calculate how much energy has been added to the water to cause the
temperature change.
b. What form of energy transfer has occurred to add energy to the
water?
c. What form of energy transfer has occurred to add energy to the
glass cup?
2. An aluminum roaster is used to cook a 6 kg turkey at 220C for 5 hours. The
roaster has a mass of 1.5 kg. When the turkey is finished cooking the
turkey is removed from the roaster and carved up. The roaster is set aside
and allowed to cool to 20C.
a. How much energy is released by the roaster as it cools?
b. Where does the energy from the roaster go as it cools?
3. The cooling system of a car contains 20 litres of water. (1 litre of water has
a mass of 1 kg).
a. What is the change in temperature of the water if the engine
operates until 836 KJ of energy has been absorbed by the water?
b. Suppose it is winter time and the water has been replaced by 20 L of
methanol (the density of methanol is 0.80 kg/L). What would be the
increase in the temperature of the methanol if it absorbed the same
836 KJ of energy?
c. Which is a better coolant, water or methanol? Explain why.
4. Silver is a metal used for making jewelry. It has a melting temperature of
962C. A jeweler has a 120 gram sample of silver she is going to use for
casting into rings.
a. If the silver starts at a room temperature of 20C, how much energy
must be added to warm the silver to its melting temperature?
b. How much additional energy must be added to melt the silver at its
melting temperature of 962C?
18
5. Mercury has a boiling temperature of 357C. Mercury vapour is dangerous
to humans because we have no way to get rid of mercury absorbed by our
body. How much energy would be required to change 10 g of liquid mercury
at 20C to mercury vapour at 357C?
6. A 2 kg block of ice is taken from a freezer set to -15C. The ice is placed in
a pressure cooker and heated until it all changes to steam at a temperature
of 120C.
a. There are three different phases that the “water” occurs in.
Describe the temperature change that occur to each phase of
“water”.
b. Calculate the energy needed to cause the temperature change of each
phase of “water”.
c. Describe each phase change that occurs to the “water”.
d. Calculate the energy needed to cause each phase change.
7. A cup contains 300 grams of hot tea at a temperature of 85C. A person
adds 30 g of creammilk (basically water) at a temperature of 4C.
a. Explain what happens to the energy levels of the tea and the
creammilk as they are mixed.
b. Calculate the equilibrium temperature of the tea/creammilk mixture.
8. In the olden days, on a cold winter night, it was common to place a hot object
in your bed to warm up the bed before you climbed in. Which would be
better at warming up the bed:
 A 2 kg iron brick heated to 90C
Or
 A 2 kg hot water bottle at 90C?
Consider specific heat capacities when providing your answer.
9. A 500 gram piece of copper is heated to a temperature of 975C. The piece
of copper is dropped into the middle of a large block of ice at 0C.
a. Why does the copper cool down?
b. What happens to the energy that the copper releases?
c. How much energy does the copper release in cooling down to 0ºC?
d. How much ice could be melted by the hot piece of copper?
19
10. A concrete bridge is measured as being 750 metres long in December when
the temperature is -25C.
a. What would be the length of the bridge on a warm summer day when
the temperature is 25C?
b. What change in length would occur if the bridge was made from steel
rather than concrete?
11. A bar of an unknkown metal has a length of 0.975 m at 45C and a length of
0.972 at 23C. What is the coefficient of linear expansion for the metal?
12. Copper cable is used in power lines to carry electricity from generating
stations to consumers. A cable is being strung between two power poles on a
hot 30C day in Saskatchewan. The two power poles are located 100 metres
from each other. What length of cable must be used so that when the
temperature reaches -60C with a windchill in the middle of January the
cable will still reach between the poles?
Answers for Homework Assignment
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a) Q=62700 J
b) Radiation
c) Conduction
a) Q=-270900 J
b) energy is transferred to surroundings (air and countertop)
a) Q=26564 J
b) Q=1248 J
i) warming Hg: Q=472 J
ii) vapourizing Hg: Q=2720 J
iii) total: Q=3192 J
a) & b) i) ice warms from -15°C to 0°C
Q=64800 J
ii) water warms from 0°C to 100°C
Q=836000 J
iii) steam warms from 100°C to 120°C Q=80800 J
c) & d) i) Ice melts to Liquid Water
Q=668000 J
ii) Liquid Water vapourizes to Steam Q=4520000 J
a) Tea loses energy and Creamilk gains energy
b) Tf=77.6°C
Pick the Hot Water Bottle: water’s higher specific heat capacity means it loses more
energy than iron for every 1 degree Celsius change in temperature
a) energy always travels from ‘hot’ to ‘cold’: conduction or convection
b)copper loses energy to the cooler ice. This melts the ice
c) Q=-187688 J
d) m=562 g
a) ΔL=0.45 m New Length=750.45 m
b) the change in length of the steel rebar is the same as the concrete sine they have the
same coefficient of linear expansion
ΔL=±0.144 m Length in summer = 100.144 m
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PHYSICS 20: Heat – Review
1. When energy is added to a substance there are two different possibilities for
the change in the molecules of the substance.
a. Explain the two effects that the addition of energy can have.
b. How would we observe the change in the molecules? We can’t see
molecules easily.
2. Sketch the graph of temperature versus time for heating ice from -20C to
steam at 115C.
3. A copper bar has a mass of 1.25 kg. The bar is heated from a temperature of
20C to 220C.
a. How much energy has the copper bar absorbed?
b. Would a bar of aluminum with the same mass show a greater or lesser
temperature change? Explain.
4. A 2.4 kg lump of iron is heated to a temperature of 240C. It is then dropped
into 6 litres of water at a temperature of 20C.
a. What happens to energy when the two are mixed?
b. Explain the heating processes which occur when the two are mixed.
c. Calculate the equilibrium temperature of the water iron mixture.
5. A 1 kg bar of gold is heated to its melting temperature and then melted.
a. How much energy does it take to melt a 1 kg bar of gold once it reaches
its melting temperature?
b. Does your answer in part a) depend on the melting temperature of gold?
Explain.
6. A copper pipe has a length of 80 metres. The pipe is used to move either water
at 4C or hot water at a temperature of 95C. What change in length would
occur for the copper pipe when it first is used with the cold water and then
with the hot water?
7. Concrete structures like bridges are reinforced with iron rebar. Compare the
coefficients of linear expansion of concrete and iron and explain why iron
rather than other metals should be used to reinforce the concrete.
8. Explain why water is a better substance than oil to use in heating or cooling
systems. Base your explanation on the specific heat capacity of water
compared to oil.
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REVIEW ANSWERS
1 a) Adding energy to a substance can increase: particle speed OR particle
spacing
b) Δ speed = Δ temperature
Δ spacing = Δ phase
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a) Copper: Q = 96250 J
b) Aluminum: temperature would be less since it has a higher specific heat
capacity (c). This means it requires more energy to change each gram by 1°C.
ΔT = 85.3°C
a) Iron bar loses energy and water gains energy. Heat energytravels from hot
to cold.
b) Conduction: collisions between fast vibrating Fe atoms and slower moving water
molecules. Fe atoms slow down and water molecules speed up.
Convection: as water warms up it becomes less dense and rises in the container.
Colder more dense water falls in the container.
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c) Tf = 29.3 °C
a) Q = 63000 J
b) No, Q = m Hf does not require a temperature
Copper: ΔL = 0.12 m
Iron and concrete have the same coefficient of linear expansion (α) value. They
change by the same amount for each degree temperature change.
The specific heat capacity of water is 4.18 j/g C. It takes 4.18 Joules of energy to
change 1 gram of water by 1 C. This is significantly higher than most other
substances. Water can transport large quantities of energy because of its high heat
capacity.
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