Heat, temperature, heat
transfer, 1st Law of
Thermodynamics
Thursday, January 28, 2015
Thursday, 1/28
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Respond to the following in your notebook, pg 24
1. What is kinetic energy?
2. What variable in the equation KE=1/2mV2 will
increase the kinetic energy of an object?
Upcoming dates:
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Thursday, 2/4 – Thermodynamics quiz
Thursday, 2/4 – Thermodynamics project due
Monday, 2/8 – Thermodynamics test and missing work deadline
Wednesday, 2/17 – Electricity quiz
Thursday, 2/25 – Electricity quiz
Monday, 2/29 – Electricity Test and missing work deadline
Friday, 3/4 – Magnetism quiz
Thursday, 3/10 – Magnetism test
Friday, 3/11 – End of the 3NWS
Heat, temperature, and equilibrium
– 7 minutes
 Go
my webpage and click on ‘heat and
temperature notes’
 Use the following questions to guide your notes.
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What is heat?
How does heat flow?
What is temperature?
What happens at when a substance reaches
equilibrium?
 Complete
the ‘check your understanding’
questions at the end of the notes.
Review notes
Heat
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Transfer of energy (macroscopic level)
Changes the average kinetic energy of
particles (particulate level).
Energy transfers from higher temperature to
lower temperatures.
An object decreases its temperature by
releasing energy in the form of heat to its
surroundings.
An object increases its temperature by gaining
energy in the form of heat from its surroundings.
Temperature
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Measures the ability of substance/physical system to
transfer energy to another substance/physical
system.
Is a measure of kinetic energy of the molecules which
make up a substance.
The temperature of a substance will
increase/decrease if the average kinetic energy of its
particles is increased/decreased.
The higher the temperature
transfer heat
The lower the temperature
receive heat
Equilibrium
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point
As long as there is a difference in temperature
between the system and surroundings, heat will be
transferred.
When the temperature difference between the
system and surroundings is zero the system and
surroundings have reached equilibrium.
Check your understanding
How is heat transferred?
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Three methods of heat transfer
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Convection
Conduction
Radiation
You will work in pairs and do the following:
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Visit the resource links to my webpage
Review the documents and take personal notes
as applicable.
Search the web for diagrams, pictures, photos,
videos of the three forms of heat transfer.
Complete the summary form(one per person).
Heat Transfer Summary Sheet
 You
will have 20 minutes to complete the
summary sheet.
 When you have finished turn it into the
black tray.
First and Second Laws of
Thermodynamics – 5 minutes
 Go
to today’s resources on my webpage and click
on ‘Laws of Thermodynamics notes’
 Use the following questions to guide your notes.
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What is Internal Energy?
What is the first law of thermodynamics?
What is a reversible and irreversible process?
What is the second law of thermodynamics?
First Law of Thermodynamics
 Energy
can be changed from one form to
another, but it cannot be created or destroyed.
 The total amount of energy and matter in the
Universe remains constant, merely changing
from one form to another.
 The First Law of Thermodynamics
(Conservation) states that energy is always
conserved, it cannot be created or destroyed. In
essence, energy can be converted from one
form into another.
Processes in nature
Types of processes
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Reversible – is a process that after it’s finished can
go backwards and end up where it started.
Irreversible – is a process that cannot go back and
restore itself
 All
processes that occur in nature are irreversible
(ex. a flower pot is dropped and shatters on the
ground – the pot cannot be restored to it’s
original state on its own).
Entropy
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Is a measure of disorder of a system
Diagram source cnx.org
Entropy
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Relating entropy to different states of matter
 When
a substance is in a gas stage there’s more
disorder than there is in a liquid stage because the
molecules are held closer together in a liquid form.
 When a substance is in a liquid stage there’s more
disorder than there is in a solid stage because the
molecules are held closer together in a solid stage.
Diagram sources www2.ucdsb.on.ca and cnx.org
Restating the 2nd Law of Thermodynamics
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Natural processes tend to move toward a state of
greater entropy.
Respond to the following
Do you think all substances/objects gain
and lose heat at the same rate? Explain
your position.
Share your response with a
neighbor
Do you think all substances/objects gain
and lose heat at the same rate? Tell your
elbow partner your thoughts and explain
your position.
What is specific heat?
 Every
substance gains or loses heat based
on its identity/physical property.
 The
physical property of a substance is its
specific heat capacity.
Examples of specific heat
What is specific heat
capacity?
 Is
the amount of heat (thermal energy)
required to raise a unit of mass of the
substance by one degree of temperature
(liquids and solids).
 Measure
of how much thermal energy is
required to change the temperature of a
substance.
What is the equation for
calculating heat change
How do you determine if heat
is gained or lost
 If
heat energy is gained Q is positive.
 If
heat energy is lost Q is negative.
Example problem
Practice Problems