Transcript Heat and Temperature

Heat and Temperature
By: Ms. Lyons
What is Heat??
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Heat = Thermal Energy!!
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Thermal Energy = the total energy of all
of the particles in a material or object.
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Throughout the ages people have invented a variety of
devices to help create and capture heat for use.
Topic 1: Using Energy from Heat
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What are some ways that we use heat?
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Cook food
Warm buildings
Dry clothes
What are some ways Thermal Energy has
been used throughout history?
Development of Heat Technologies
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What heat technologies can you think of
that have been developed through-out
time? Why have they changed?
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Examples….
Devices to generate, transfer,
control or remove heat
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Heat = Thermal energy
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Can you think of any examples of devices
that generate, transfer, control or remove
heat?
Topic 2: Measuring Temperature
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Thermometer: Mechanical or electrical device for
measuring temperature. Early thermometer was
invented by Galileo.
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Scale: A series of equally measured sections that are
marked and numbered for use in measurement.
Celsius Scale
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Celsius Scale: Most commonly used in Canada. Unit of
temperature is called a degree. Based on the boiling and
freezing points of water.
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Boiling Point: The temperature at which water boils.
100o C at sea level.
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Freezing Point: The temperature at which water
freezes. 0o C at sea level.
Another Scale…
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Kelvin is another way of measuring
temperature.
Scientists use Kelvin to explain the
behaviour of gases.
“Absolute Zero” is measured in Kelvin –
which is the coldest possible temperature
0 Kelvin = -273 ºC
Right Device for the Job
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Each thermometer has a sensor – a
material which is affected by changes in
the environment (such as temperature)
The sensor produces a signal (information
about temperature, such as an electrical
current) which affects a responder (a
pointer, light or other mechanism that uses
the signal in some way)
The Thermocouple
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Wires made up of two different
metals are twisted together.
When the wire tips are heated,
a small electric current is
generated
The amount of current
depends on the temperature.
They can measure higher
temperatures than
thermometers.
The electric current can be
used to turn switches on or off
if the temperature changes.
Used in kilns, diesel engines
and industrial furnaces
Bimetallic Strip
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Made of two different
metals joined together
When the strip is heated
one metal expands more
than the other
Thus the strip coils more
tightly
Movement of the strip
can operate a switch that
can control
furnaces…commonly
used in thermostats in
homes
Your Brain…(extra)
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Your brain has its own temperature
sensor.
It monitors your own internal temperature.
If the temperature outside changes, the
sensor signals your brain to release
chemicals that will help your body adjust
to normal temperature (37°C)
Continued
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Recording Thermometer: A bimetallic strip
connected to a writing device and paper
which records temperature fluctuations
over time.
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Infrared Thermogram: Records infrared
radiation, (heat sensor) as different colors
according to their temperature.
Topic 3: Particle Model of Matter,
Temperature and Thermal Energy
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Reminder: matter is anything that takes up
space
Three most important ideas of the model:
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All substances are made of particles too small
to see
The particles are always in motion
The particles have space between them
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When motion of
particles increases –
so does the
temperature
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When motion of
particles decreases
– so does the
temperature
Temperature indicates the average speed of particle motion
in a substance
Glow Stick Demonstration
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What will happen to
the glow stick when it
is placed in hot
water?
What will happen to
the glow stick when it
is placed in cold
water?
Energy
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Energy is the ability to do work – in other
words to cause change
In order for something to change, there
must be a transfer of energy from one
thing to another
Ex. Charged batteries run your iPod,
dead batteries would not
Thermal Energy
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Energy associated with hot objects
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What gives off thermal energy?
What Energy is…and is not
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Energy is not a substance.
It cannot be weighed
It does not take up space
Energy describes a condition
Law of Conservation of Energy: Energy cannot be created or
destroyed. It can only be transformed from one type to another
or passed from one object to another
Temperature vs. Thermal Energy
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Temperature = A measure of the average
energy of the particles in a material.
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Thermal Energy = The total energy of all
the particles in a material.
What is the difference??
Topic 4: Expansion and
Contraction
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Contract: Decrease in volume
Expand: Increase in volume
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Temperature changes cause things to expand and
contract
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Heated – usually causes expansion
Cooled – usually causes contraction
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Usually more drastic in gases, then liquids then solids
Topic 5: The Particle Model and
Changes of State
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Heat Capacity: Amount of thermal energy
that warms or cools the object by one
degree Celsius.
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Specific Heat Capacity: Amount of
thermal energy that warms or cools one
gram of a material by one degree Celsius.
Sample Specific Heat Capacity
Table
Solids
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Solids have definite shape and volume
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Cannot be compressed into smaller objects
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When solids are heated – they expand
When solids are cooled – they contract
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Liquids
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Liquids have definite volume but no shape
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Cannot be compressed (meaning if I have 1
litre of coke, I cannot make it fit into a pop
can)
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When liquids are heated – they expand
When liquids are cooled – they contract
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Gases
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Have no definite shape or size
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Can be compressed
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When heated, gases – expand
When cooled, gases - contract
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Changes of State
Definitions:
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Define, in your notes, each of the following:
 Melt
 Freeze
 Evaporate
 Condense
 Sublimation
Continued
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Evaporative Cooling: A process in which the
faster moving particles on the surface of a liquid
evaporate and escape into the air, the slower
ones are left behind creating a lower average
kinetic energy (cooling it)
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Particles are more or less organized when they
are hot or cold????
Phase Changing
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During a change from solid to liquid or liquid to gas the
average temperature does not change even though heat
is being added, the name for the heat that is added is
latent heat.
Topic 6: Transferring Energy
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There are 3 main ways to transfer energy
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1) Radiation
2) Conduction
3) Convection
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***See handout***
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Transferring Energy Continued
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Energy Source: An object or material that
can transfer its energy to other objects.
Radiation: The transfer of energy without
any movement of matter.
Radiant Energy: (a.k.a. EMR) Energy
that is transferred by radiation.
Radiant Energy
All forms of radiant energy share several
characteristics:
- They behave like waves
- They can be absorbed and reflected by
objects
- They travel across empty space at the
same high speed of 300,000 km/s
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Conduction and Insulation
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Thermal Conduction: The process of
transferring thermal energy through direct
collisions between particles.
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Examples of good conductors???
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Heat Insulators: Are very poor conductors
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Examples???
Topic 7: Sources of Thermal
Energy
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Energy appears in many forms
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Potential Energy: Stored energy
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E.g. elastic pulled back and ready to be shot.
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Kinetic Energy: Energy of motion
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Examples??
Chemical Energy
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Stored chemical energy is released in the
form of thermal energy when it is burned.
Electrical Energy
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Electricity
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Example: hydro-electric dams – falling water is
changed to electrical energy
Geothermal Energy
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Energy that we get from the Earth’s interior
Solar Energy
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Energy from the sun
Passive Solar Heating
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Uses materials in the
structure to absorb,
store, and release
solar energy.
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Example: a wall of
windows
Active Solar Energy
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Uses mechanical
devices to distribute
stored thermal energy
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Example: fans
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Solar Collectors – use
stored water or air on the
roof, heats it, and then
pumps it through the
building
Wind Energy
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Moving air
Is a result of solar
energy – as the sun
heats the air, the
warmer air rises and
cools off. Cooler air
falls, creating a
convection current –
this forms wind
Fossil Fuels
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Chemicals made from plants and animals that died and
decomposed millions of years ago and have preserved
deep underground.
Energy Converters
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Energy can be converted into another form.
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For example a candle can convert chemical
energy into heat and light energy.
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Candles are energy converters (devices which
convert or change energy from one form to
another.)
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Other examples????
Renewable Resources
Definition:
Renewable resources
are a natural resource
that grow at about the
same rate they are
used up.
Non-Renewable Resource
Definition:
A resource which
is limited in
supply and
cannot be
replaced once it
is used.
Renewable Resources in Alberta
Examples:
 Trees (Forestry)
 Wind (Wind Farms)
 Agriculture ( One of the biggest crop
producers in Canada)
 Water (Dams and water conservation)
 Solar ( Solar Panels and Solariums)
Non-Renewable Resources in
Alberta
Examples:
 Oil (Oil Wells)
 Natural Gas (Pipelines across the
province)
 Coal (Mining in Alberta)
Positive and Negative Effects On
Our Environment
Positive (Renewable)
 Plentiful
 Non-polluting
 Low cost to acquire
 Cogeneration
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Negative (nonrenewable)
Polluting –
greenhouse gases,
thermal pollution
Expensive
Can be rare
Not plentiful
Greenhouse Gases –
do not write down
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Even though carbon dioxide occurs naturally in
the environment (we breathe out CO2 and plants
require CO2), it, like anything is only good in
moderation. When there is too much CO2 in the
air, heat from Earth is unable to escape into
space because it is trapped by greenhouse
gases (which have a lot of CO2 in them) –
scientist believe that this leads to GLOBAL
WARMING
Global Warming
do not write down
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When there is an increase in CO2 and
greenhouse gases are trapping thermal energy
– the Earth’s temperature increases rapidly. A
few degrees doesn’t seem to affect us much, but
to the Earth, it can make a huge difference. It
can change climate zones, plant growing
abilities, dry up rivers and lakes, and even melt
polar ice caps….What are some effects on the
surrounding environments if these things
happen?
Cogeneration
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Sometimes negative effects can be turned into
more positive effects – cogeneration uses
waste from thermal pollution to produce
electricity or uses the waste to heat buildings.
FACT: when fuel burns in a thermo-electric
power plant, only about 1/3 of its energy is
converted into electricity – cogeneration is
efficient because it uses some of the remaining
2/3 of energy
The Three Important Renewable
Resources to me and Why?
1.
2.
Water: Very important to me since I need
water to survive. Water is a very good
way to generate energy so that I may
have electricity in my home.
Agriculture: It is the most important to
me since I need food to live. It provides
me with produce to eat and clothes that I
may wear.
Continued
3.
Sun: The sun gives me energy to go to
school everyday. It provides me with light
so that I am not always walking around
in the dark. It also makes things grow.
The best part is that you can capture the
sun and turn it into energy that can be
used.
Renewable Resources
Lab Activity…
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How else do energy resources affect our
environment?
In this lab we will look at how renewable
resources and our environment are affected
by pollution – specifically OIL SPILLS
Topic 8: Conserving Our Fossil
Fuel Resources
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Insulate homes and water lines
Reduce the amount of energy we use
Install a programmable thermostat
Carpool
Others????