Temperature and the Phases of Matter

flinkexistenceMechanics

Oct 27, 2013 (3 years and 10 months ago)

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Temperature and the Phases of Matter

Key Question:

What is temperature?

GPS
:

SP3.

Students will evaluate the forms and transformations of energy.

a.
Analyze, evaluate, and apply the principle of conservation of energy and
measure the components of work
-
energy theorem by


describing total energy in a closed system.


relating transformations of potential energy to kinetic energy.

f.
Analyze the relationship between temperature, internal energy, and work
done in a physical system.

ESSENTIAL QUESTION
?

Why does society spend a lot of resources on controlling thermal energy?

Temperature and the Phases of Matter


In the Fahrenheit scale
, water freezes at 32 degrees
and boils at 212 degrees


The
Celsius scale

divides the difference between the
freezing and boiling points of water into 100 degrees
(instead of 180).

Converting temperatures


A friend in Paris
sends you a recipe
for a cake.



The French recipe says to bake
the cake at a temperature of
200
°
C for 45 minutes.


At what temperature should
you set your oven, which reads
temperature in Fahrenheit?

Temperature and the Phases of Matter


Temperature

measures the
kinetic energy per atom due
to random motion.

SOLID

GAS

LIQUID

MELTING

FREEZING

EVAPORATION

CONDENSATION

SUBLIMATION

DEPOSITION

3 PHASES OF MATTER

Phase changes


When
thermal energy

is added or subtracted from
a material,
either

the temperature changes,
or

the
phase changes, but usually not both at the same
time.

Heat and Thermal Energy

Key Question:


What is the relationship
between heat,
temperature, and energy?

Heat and Thermal Energy


Temperature

is NOT the same as thermal
energy.


Thermal energy

is energy stored in materials
because of differences in temperature.


The thermal energy of an object is the
total

amount of random kinetic energy for
all
the
atoms in the object.


Remember, temperature measures the random
kinetic energy of
each
atom.


Heat and Thermal Energy


Imagine heating a cup of
coffee to a temperature of
100
°
C.


Next think about heating up
1,000 cups of coffee to
100
°
C.


The final temperature is the
same in both cases but the
amount of energy needed

is
very different.

Heat and Thermal Energy


Heat

is what we call thermal
energy that is
moving
.


The
joule

(J) is the unit of
heat (or thermal energy)
used for physics and
engineering.


The
calorie

is a unit of heat
often used in chemistry.

Heat flows from the hot coffee
to the cooler air in the room.


Specific Heat


The
specific heat

is the quantity of heat it takes
to raise the temperature of one kilogram of
material by one degree Celsius.

Specific Heat


The temperature of
gold rises quickly
compared with water
because its specific
heat is much less
than the specific heat
of water.


Heat Equation

E = mc
p
(T
2
-
T
1
)

Specific heat (J/kg
o
C)

Mass (kg)

Heat energy (J)

Change in

Temperature

(
o
C)

Calculate Heat


One kilogram of water is heated in
a microwave oven that delivers 500
watts of heat to the water.


One watt is a flow of energy of one
joule per second.


If the water starts at 10
°
C, how
much time does it take to heat up to
100
°
C?

First Law of Thermodynamics


Energy loss
is equal to

energy gain.

Second Law of Thermodynamics

Application: The Refrigerator