What do you think?
Place the 2 groups of objects
below in order from coldest
to hottest.
1. Cheese, popsicle, napkin
2. Bonfire, napkin, fried egg
So…
• Is the napkin hot or cold?
(Chapter Eleven)
Temperature,
Phases of Matter
and
Heat
Back to the hot and cold …
• Using the words “hot” or “cold” can
sometimes be confusing…or relative
(some of
you think the room is too cold…some don’t)
• To reduce confusion, an object should be
described by its temperature.
• SUBJECTIVE
vs
OBJECTIVE
Temperature
• Is a measure of the kinetic energy of the
particles in an object.
• The faster the particles move, the higher the
temperature
• Temperature is independent of the amount of
the substance being measured (a little bit can have
the same temperature as a whole bunch)
Temperature
There are two common
temperature scales.
The Celsius scale:
Water freezes at 0 C
Water boils at 100 C
(metric)
On the Fahrenheit scale:
Water freezes at 32 F
Water boils at 212 F.
(English or standard)
The
rd
3
Temperature Scale (though
not so common)
• Kelvin (K) – SI unit – starts at
absolute zero
• NO degrees, labelled in “Kelvins”
• Fahrenheit (oF) – US unit
• Celsius (oC) – metric unit – broken into 100
equal units between freezing and boiling
water
Absolute zero
Absolute zero is
-273°C.
You cannot have a
temperature lower
than absolute zero.
Think of absolute zero
as the temperature at
which atoms are
“frozen.”
Thermometer
A thermometer is an
instrument that
measures temperature
Thermometers you have
likely seen uses colored
liquid alcohol to sense
temperature- because alcohol
stays liquid over a wide
range of temperatures.
How does a thermometer work?
• They work due to thermal expansion
• As a substance gets hotter, its particles move
faster. The particles do not expand, but they
need to spread out…this spreading is called
thermal expansion.
• When the thermometer is warmed, the liquid
inside expands and rises up in the tube.
Thermal Expansion
1. object is heated up
2. particle movement
increases
3. particles spread out
Thermal Contraction
1. object cools down
2. particle movement
decreases
3. Particles stay closer
together.
Converting to Kelvin
The Kelvin temperature
scale is useful in science
because it starts at
absolute zero.
To convert from Celsius to
Kelvin, you add 273 to the
temperature in Celsius
Let’s convert...
• What temperature was it this morning when
you got up?
• Let’s convert it to Celcius:
Another temperature conversion…
• Look at the conversion formulas earlier in your
notes.
• It is 77 in this room.
• What unit would that be in?
• Let’s convert that number to the other 2
units.
What temperature really is…
Temperature measures the kinetic
energy per atom due to random
motion. (how fast the molecules
are moving)
What temperature really is…
The back-and-forth jiggling
of atoms is caused by
thermal energy, which is a
kind of kinetic energy- (E an
object possesses due to
temperature)
BROWNIAN
MOTION.
Atoms are in constant
motion, even in a solid
object.
More on temperature (without
having to listen to me)!
1. Watch “Brainpop” on Temperature
2. Take review quiz on Temp.
Tell your neighbor!
1.) Why can’t there be a temperature lower than
absolute zero?
2.) Explain the scientific meaning of the word
random.
3.) Which is colder, 0 ˚C or 20 ˚F ?
More tomorrow…
What is heat?
• Heat is energy of the
atom that is moving.
• Heat flows any time there
is a difference in
temperature.
• Because your hand has
more thermal energy than
the chocolate, thermal
energy flows from your
hand to the chocolate and
the chocolate begins to
melt.
Soda and Heat
• How does soda
get cold in a
cooler of ice?
What is Thermal Energy
• Remember, temperature is the measure of
particle movement due to temperature
)(kinetic energy)…..however, the TOTAL energy
in ALL of the particles in a substance is called
its thermal energy….
• the more particles there are, the more thermal
energy it contains.
What is Temperature again?
Heat, Temperature, and Thermal
Energy
• Heat, temperature,
and thermal energy
are related, but are not
the same thing.
• The amount of thermal
energy depends on the
temperature but it also
depends on the amount
of matter you have.
HEAT TEMPERATURE
and THERMAL ENERGY
Units of heat and
thermal energy
• The metric unit for
measuring heat is
the joule.
• This is the same
joule used to
measure all forms
of energy, not just
heat.
How are calories related
to heat?
• How can you determine how much “energy” is
contained in a substance?
• Use a calorimeter. It uses the amount of heat
generated by burning something as a measure
of how much energy it contains.
Heat and thermal energy
• Thermal energy is often measured in
calories.
• One calorie is the amount of energy it
takes to raise the temperature of one
milliliter of water by one degree Celsius.
How a calorimeter works:
1. Food to be tested is
burned below a container
of water.
2. The temperature increase
in the water is measured.
3. A calorie is the amount of
energy needed to change
the temp 1 gram of water
by 1oC.
Heat Transfer
There are three ways that heat is transferred:
1. Thermal Conduction
2. Convection
3. Thermal Radiation
Thermal Conduction
Heat conduction is the transfer of
heat by the direct contact of
particles of matter.
Conduction occurs between two
materials at different
temperatures when they are
touching each other.
Where is the heat energy conducted to and
from in this system?
Examples of Conduction
• direct contact
Thermal conductors and insulators
• Materials that
conduct heat
easily are called
thermal
conductors and
those that
conduct heat
poorly are called
thermal
insulators.
Is a down coat a
conductor or an
insulator?
• Substances that
transfer heat easily
are called
conductors
• The best conductors
are metals.
• Substances that do
not conduct thermal
energy very well are
called insulators.
Application
• For years, the
plumbing in homes
was done in copper
piping. Now they
are done in PVC.
What are some
reasons that this
change occurred?
Convection
• Convection is the transfer
of heat through the
motion of matter such as
air and water.
• In a container, warmer
fluid rises to the top and
cooler fluid sinks to the
bottom.
• This is called natural
convection.
Convection
Convection
• Convection is mainly what distributes
heat throughout a room.
Radiation
• Transfer of heat through electromagnetic
waves across empty space.
Thermal radiation
• Heat from the Sun is
transferred to Earth by
thermal radiation.
• The higher the
temperature of an object,
the more thermal
radiation it emits.
• All the energy the Earth
receives from the Sun
comes from thermal
radiation.
Thermal radiation
• Thermal radiation is also
absorbed by objects.
• The amount of thermal
radiation absorbed depends
on the surface of a material.
• Dark surfaces absorb most
of the thermal radiation they
receive.
• Silver or mirrored surfaces
reflect thermal radiation
Equilibrium
• Thermal equilibrium occurs when two
bodies have the same temperature.
• No heat flows in thermal equilibrium
because the temperature is the same in
the two materials.
I remember that!
1.) What are the three ways heat is transferred?
2.) Heat from the Sun is transferred by _______
_________.
3.) When heat is transferred by two objects
touching, it is called _____________.
HEAT TRANSFER VENN DIAGRAM
STATES OF MATTER
Solid
Liquid
Gas
AND
?????
The Phases of Matter
Intermolecular forces tend to bring molecules
together. Intermolecular forces have to be
overcome in order to change phase.
Sing it Baby….
http://www.youtube.com/watch?v=btGu9FWSPtc
Solid
A solid holds its shape and
does not flow.
The molecules in a solid
vibrate in place, but on
average, don’t move far
from their places
Liquid
A liquid holds its volume, but
does not hold its shape—it
flows.
Liquids flow because the
molecules can move around.
Gas
A gas flows like a liquid, but
can also expand or contract
to fill a container.
A gas does not hold its
volume.
The molecules in a gas have
enough energy to completely
break away from each other.
Plasma
• At temperatures greater than 10,000˚C, the
atoms start to come apart and become a
plasma.
• Atoms are broken apart into separate positive
ions and negative electrons
• Conducts electricity and is formed in
lightening and inside stars.
I remember that!
1.) What are the three phases of matter?
2.) Liquid holds its volume, but does not hold
its ___________ .
3.) The melting point and the freezing
point for water is ___ degrees Celsius.
Phases of Matter
http://www.youtube.com/watch?v=KxtqzApPAfc
9:12
Phases of Matter and Phase
Change
•
•
•
•
•
•
Boiling point
Melting point
Freezing point
Vaporization/evaporation
Condensation
Phase Change Diagram
Boiling Point
The temperature at which a
liquid becomes a gas is called
the boiling point.
Vaporizaton and Evaporation
• Also known as the boiling point
• When liquid turns to vapor (gas)
Melting Point
The melting point is the temperature
at which a substance changes from a
solid to a liquid.
Freezing Point
The freezing point is the temperature
at which a substance changes from a
liquid to a solid.
Condensation
Condensation is the point at which a
substance changes from a gas to a
liquid.
Melting and boiling points of
common substances
Materials have a
wide range of
melting and
boiling points.
So what?
• So what really is the difference between the
boiling point and the condensation point of a
substance?
• So what really is the difference between the
freezing point and the melting point of a
substance?
Phase Change Diagram
DO NOW:
Quick Quiz – True/False
1. Heat is the transfer of energy between
two objects with different
temperatures.
2. Conduction occurs in fluids.
3. Convection currents result from
temperature differences in gases and
liquids.
4. Radiation is the means by which the
energy from the sun is transferred to
Earth.