Download Chapter 10 Heat and Heat Technology (PS 7)

Chapter 10 Heat and Heat Technology
Word
Ball & Ring Set
Demonstration
(PS 7)
Name ____________________________
Explanation
What happened when ball was heated?
The ball wouldn't fit through the ring - the
ball got larger/metal expanded
Drawings/Examples
What happened when the ball was placed in
water?
The water vaporized to steam/energy from the
metal transferred quickly to the water (high to
low temp) so the ball contracted and fit back
through the ring
Temperature
(BrainPop)
The measure of the AVERAGE ___kinetic
energy___ of the particles/molecules in an
object. (not all particles moved at the same
speed)
NOT affected by amount:
Temp _is not__ determined by how much of a
substance you have so a pot of tea __will___
have the same temperature as a cup of tea
poured from the pot even though there is
more tea in the pot.
Same temp when you first pour!
More energy = higher temp!
Kinetic Energy of
Particles
The __movement___ of the object's particles the __faster___ the particles are moving, the
_more___ kinetic energy they have.
Temperature:
Used in Science: Celsius & Kelvin (SI)
100 ºC
Celsius
Celsius - Unit__ºC__
Boiling Point__100 ºC __
Freezing Point __0 ºC ___
Room Temp ___20 ºC ___
Kelvin - Unit _K__ (no degree sign/ no
negative numbers)
Boiling Point ___373 K__
Freezing Point __273 K__
Room Temp _293 K__
373 K
Kelvin
0ºC
273 K
Zero Kelvin = 0 K
Absolute Zero
The _lowest_ point on the Kelvin scale when
all molecular motion ceases/stops.
Thermal
Expansion
Heat
The increase in _ volume_ of a substance due
to an __increased___ change in temperature
because the molecules move __faster__ and
__spread apart__, taking up more space (
___volume__ ). The particles themselves
don't expand... they spread out causing the
whole object to expand and take up more
space (less attraction between the particles)
Ex: bridge joins and alcohol in
thermometers (expands when
higher temp)
Most substances _contract_
when cooled and energy is
__released_. The temperature
_decreases_ as the average
kinetic energy __decreases_.
Unit __Calories / (C) or Joules (J)__
The _TRANSFER_ of energy between
objects that are at different _temperatures__
(BrainPop)
Transfer enough energy & you get a change
of state – physical change!
Temperature
vs
Temperature is a measure of the average
amount of __Kinetic Energy__ and heat is the
__transfer_ of energy due to a difference in
temperature.
Heat
Thermal Energy
(TE)
Relationship
between
Heat and
Thermal Energy
Pick up a wooden vs a metal
spoon. Why does the metal
spoon "feel cold" and the
wooden spoon does not? (hint:
think about insulators &
conductors) you are transferring
energy from your hand to the
metal spoon but not so much
energy from your hand to the
wooden spoon
Insulators don’t transfer energy
Low or high amounts of TE?
The __TOTAL_ amount of energy of __all__
the particles in a substance.
Unit: __Joules (J)___
High temp = _more_ thermal energy
Low temp = _less__ thermal energy
Why? the higher temp is due to the particles
moving faster and therefore more movement
= more TE
More particles = __more__ thermal energy
More particle movement = _more__ thermal
energy.
True or False: A cup of hot coffee has the
same amount of thermal energy as a cup of
iced coffee.
Does thermal energy depend
partly on temperature? Yes,
because the amount of
movement determines the
amount of TE
Which has more
Thermal Energy
- pot or cup of
same temp. tea?
Pot because it has more
particles... but the temperature
would be the same
Energy is always transferred from the object with the ____higher______temperature to the object with
the ___lower_______ temperature until both objects reach the ___same___ temperature. This will
continue until both objects reach the same temperature and is called _____thermal equilibrium___.
One object may have more thermal energy because there is more of it, but both objects would have the
same temperature.
So, why does the ice melt in a cooler when you add cans or bottles of drinks that are at room
temperature? Because the energy from the higher temp drinks is transferred to the lower temp ice until
the temperature of everything is equal
Word
*Conduction
(Energy Transfer)
Explanation
The __transfer___ of thermal energy through
____direct contact___ - requires matter.
Drawings/Examples
Touch the metal
spoon that has been
sitting in the
boiling soup on
the stove. Why
did the spoon
get hot? Because the transfer of
energy from the soup to the
spoon and then transferred to
your hand when you touched the
spoon.
Substances that transfer thermal energy well
Example:
Metals
Substances that do not transfer thermal energy
well (may slow the transfer or reduce the
amount of transfer)
The __transfer__ of thermal energy by
movement of __liquids_ or __gasses__.
(called “fluids” in the CE Lab)
Examples:
Glass, rubber, plastic, wood,
insulation, paper, fabrics
Drop food coloring into
different temps of water. What
happened in the
Low Temp Particles not moving quickly so
spread slowly
Higher Temp - Particles moving
quickly so spread
quickly...warmer water rises &
cooler water sinks
Examples: heat/cooling our
homes (where are our vents?),
warming a swimming pool,
convection oven
Conductor
Insulator
*Convection
(Energy Transfer)
Convection flow & density...
Denser air/liquid (cooler/lower temp contracts) _sinks__ and pushes the less dense
(warmer/higher temp - expands) air/liquid
_up_
*Radiation
(Energy Transfer)
Examples: campfire or sun
The __transfer_ of thermal energy through
Or the waves of energy radiating
__matter___or ___space__ as electromagnetic off of the asphalt on a hot day
__waves__. No matter needed!
Greenhouse Effect
Thermal Conductivity - the rate at which
substances conduct thermal energy
Heat &
Temperature
Change
Which will reach a higher temperature faster?
Why? metals are good conductors
Silver coins or water
Cooper pan on a stove or its wooden handle
Unit: _______________
The amount of energy needed to change the
Specific Heat
__temperature___ of 1 kg of a substance by
Capacity
1 ºC
Water 4284 J/kgºC / Sand 830 J/kgºC
(Why coastal areas Low Specific Heat (gain/lose energy easily) stay warmer longer gain a little energy & temp increases quickly
than inland areas) Example: metals (conductors!)
– water has a
High Specific Heat (gain/lose energy slowly)higher specific
need to gain a lot of energy in order to
heat capacity
increase temp
compared to land Example: water – used in LOTS of systems
to remove excess TE – cars/home
As thermal energy is added to or taken away
Phase Change & from a system, the temperature does not
Temperature
always change! There is no change in
temperature during a __phase change____
because the energy is being used to make or
break bonds between molecules, but not
change the temperature. Change in amount of
energy!
Air is heated by a furnace and the fan
Heat Pump
forces/pumps the heated/high temp air
(Heat Technology) through a system of ducts to the vents in each
room. The cooler/low temp air returns
through the "intake" where you put your air
filters. (convection currents)
Thermostat
Uses __thermal expansion__ of metal inside
(Heat Technology) to turn on/off the AC or heat
Refrigerator
(Heat Technology)
___Removes__ the higher temp air using a
coolant that removes the thermal energy
Heat Engine
(Heat Technology)
Devices that convert __thermal__ energy into
__mechanical__ energy.
Geothermal
Systems
(Heat Technology)
Thermal Pollution
Changes the thermal energy in the ground
(temp around 50ºF) into useful energy for
homes/buildings
The excessive heating of a body of
____water___ by power plants or industrial
plants
Why is the metal buckle of a
seat belt at a much higher
temperature than the cloth seat
belt in a car on a hot/high temp
day? metal has low specific
heat capacity and gets hotter
quicker with just a little bit of
heat whereas the cloth has a
higher specific heat capacity and
it takes a lot of energy to raise
its temperature
Heat Transfer Investigation
TWO
Freezing/melting occur at same
temp! Condensation and
vaporization occur at same
temp!
Pg 264
Also used for AC system –
removes thermal energy
Pg 250 - bimetallic strip
expands/contracts to open/close
circuit
Pg 268
Pg 266 Internal combustion
engine - ex: car or lawn mower
engine
External combustion engine ex: rocket
Ex: hot water heaters,
heat pumps, geothermal power
plants
Pg 269 Ex: water used to cool
machines, now at higher temp, is
dumped into ponds/lakes