Drill December 17, 2015
Identify which of the two descriptions of your
class is an intensive property and which is
extensive:
 The number of students in the class.
 The grade level of the students in class.
Define the following:
 Thermodynamics
 System
 Property
Drill
Fill in the blanks:
 “Dynamis” is Greek for ________.
Matter and Energy
Objectives: SWBAT:
1. Differentiate between Closed and Open
Systems; Intensive and Extensive Properties;
Property and State.
Matter and Energy
This course is an introduction to the study
of thermodynamics and an investigation of
how it can be applied to renewable and nonrenewable energy sources.
Thermodynamics - study of systems and energy transfer
System – what we choose to study
Boundary – separates system from surroundings
Surroundings – everything outside of system
Matter and Energy
Thermodynamics - “the study of systems and energy transfer”
There are two types of systems…
Closed Systems – no mass crosses the boundary
Open Systems – mass crosses the boundary
“Energy can cross the boundary of
both open and closed systems.”
Energy in…
Energy out…
Matter and Energy
Property – a characteristic used to describe a system
There are two types of properties:
1) Extensive – the whole equals the sum of its parts
2) Intensive – the whole is the same as any part
EXTENSIVE
Mass
Volume
INTENSIVE
Temperature
Pressure
Mass Temperature
and Volume
are
both
extensive
properties.
Mass,
Extensive
properties
andusually
Pressure
use
arecapital
exceptions
letters
to as
thesymbols.
rule:
Temperature
and Pressure
are
properties.
Extensive
Mass
(m) isproperties
extensive;
usually
Temperature
useintensive
lower
(T) case
and
Pressure
letters as(P) are
symbols.
intensive.
Matter and Energy
Property – a characteristic used to describe a system
Property
Symbol Definition
Mass
m
measure of the amount of material present
Volume
V
amount of space occupied by an object
Energy
E
the ability to do work or produce heat
Temperature
T
measure of the molecular activity of a
substance
Pressure
P
force exerted per unit area on the boundaries
of a substance
Density
ρ
the total mass of a substance divided by the
total volume
What type of property is density, ρ? Intensive
What type of property is energy, E? Extensive
Matter and Energy
Property – a characteristic used to describe a system
In general, an extensive property can be made intensive by
dividing by the mass of the system.
Extensive
Divide by Mass
Intensive
Energy
E
kilojoules, kJ
Energy/mass
E/m
kilojoules/kilogram
Specific Energy
e
kJ/kg
When an extensive property is made intensive by
dividing by mass, we use a lowercase symbol and the
prefix “specific”.
HOMEWORK
Define the following properties:
 Specific volume
 Density
 Specific gravity
 Humidity

Matter and Energy
Specific volume: is the total volume of a
substance divided by the total mass of that
substance. .. Units ?
Matter and Energy
Density: is the total mass of a substance
divided by the total volume occupied by
that substance… Units?
Matter and Energy
Specific gravity: is the measure of the
relative density of water at a standard
temperature. For engineers we use the
temperature of 60deg. F
Matter and Energy
Humidity: is the amount of moisture
(water vapor) in the air. It can be
expressed as absolute or relative
humidity. Absolute humidity is the mass
of water vapor divided by a unit of
volume of air (g of water/ cm3 of air.
Relative humidity is expressed as a %.
Matter and Energy
Property – a characteristic used to describe a system
Let’s work an example:
A closed steel tank contains 3 kg of water in the form of
vapor and liquid. The volume of the tank is 18 m3. Calculate
the specific volume of the water in the tank:
v=18 m3 , m= 3 kg
v=V/m
v=18m3 /3 kg
v= 6 m3 /kg
Matter and Energy
Property – a characteristic used to describe a system
A closed steel tank contains 3 kg of water in the form of
vapor and liquid. The specific energy of the water in the tank
is 126 kJ/kg. Calculate the total energy of the water in the
tank:
E=126 kJ/kg,
m= 3 kg
Specific Energy (e) = Energy/mass
Energy= Specific Energy X Mass
E=exm
E = 126 kJ/kg x 3 kg
E = 378 kJ
Matter and Energy
Property – a characteristic used to describe a system
State –are
a listtwo
of alltypes
the property
values of a system
There
of properties:
1) Extensive – the whole equals the sum of its parts
2) Intensive – the whole is the same as any part
To truly
We
nowdescribe
know that
a system,
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you help
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change
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properties
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must when
know
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state
and how
of
changes,
thefrom
stateintensive
of the system
also changes.
to convert
that
system.
to extensive
and vice versa.
Matter and Energy
Property – a characteristic used to describe a system
State – a list of all the property values of a system
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Energy
6
Mass
Temperature
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