View
224
Download
1
Category
Tags:
Preview:
Citation preview
Heat & TemperatureUnit C
Heat and Temperature
1. Using Energy from Heat2. Measuring Temperature3. The Particle Model, Temperature
and Thermal Energy4. Expansion and Contraction5. The Particle Model and Changes of
State6. Transferring Energy7. Sources of Thermal Energy8. Conserving Our Fossil Fuels
Topic 1: Using Energy From Heat
Thermal Energy, heat and infrared radiation are all the same.
We have always used heat in different forms and technology has changed the way we get our heat energy.
Think about it!
How do people use thermal energy?
How have these uses changed over time?
How were people able to stay warm enough to live in soddies?
Measuring TemperatureTopic 2
Temperature is the average kinetic energy of a substance
Heat is the total kinetic energy of a substance
Measuring Temperature
Temperature can show how hot or cold something is.
Touch and sight can help us determine the temperature of something
When we talk about temperature how can we describe it accurately? Cold, colder, coldest Hot, hotter, hottest
Thermometers
Thermo = related to heat
Meter = method of measurement
Galileo invented the first thermometer around 1600
What’s missing from these 1700’s thermometers?
Thermometers
The first precise thermometers were created by Fahrenheit
The most commonly used scale was created by Anders Celsius in 1742
Temperature Scales – Celsius
Celsius based his scale on the properties of water at sea level 0 – the temperature at which ices melts 100 – the temperature at which water
boils The space was divided into 100 equal
units
The two temperatures can be used to calibrate a thermometer (p. 195)
Temperature Scales – Celsius Pressure can affect the freezing and
boiling point of water High pressure can allow ice to melt at
lower temperatures than 0˚C Ice skates Glide on a thin layer of water
Low pressure can allow water to boil at a lower temperature than 100˚C Water boils at about 69˚C on Mt. Everest
Impurities affect freezing and boiling points as well. Salt water boils hotter than 100˚C
Think about it!
Would the boiling point of water be higher or lower in Brooks than in Vancouver?
Temperature Scales – Kelvin
Absolute Zero is the coldest possible temperature; -273.15˚C
Lord Kelvin developed the a scientific scale based on Absolute Zero 0˚C = 273.15K
What is the hottest temperature ever?
Think about it!
How could you measure the temperature of: Your body? An ice burg? Your house? The sun?
Can you use the same device for everything? Why or why not?
Measuring Temperature
Different devices need to be used to measure different substances
Thermometers must have: A sensor – a material affected by
changes in some feature of the environment (temperature)
A signal – provides information about the temperature (an electric current)
A responder – something that communicates the information sent by the signal from the responder
Measuring Temperature Thermocouples
Two wires are twisted together The tips sense the temperature and
a current is created The current increases with the
temperature
Measuring TemperatureThermocouple
Measuring TemperatureBimetallic Strip
A bimetallic strip is made of two metals joined together
As it is heated one metal expands faster than the other, curling the strip
Sometimes the movement of the strip controls a switch, like in a thermostat. Thermo – related to heat stat – stabilize, make constant
Measuring TemperatureBimetallic Strip
Measuring TemperatureRecording Thermometer
When a bimetallic strip is attached to an arm, with a marker and a graph paper drum, it can record temperature
It is similar to a seismograph
Measuring TemperatureInfrared Thermogram
Anything warmer than Absolute Zero gives off infrared radiation
IR (infrared radiation) can be photographed and shown on special film or displayed on a screen
The colour displayed demonstrates the temperature of the object
Measuring TemperatureInfrared Thermogram
An Infrared Thermogram is the tool used to measure the temperature
Think About it!
How would you measure the temperature for each of the following: Your body? An ice burg? Your house? The sun?
How hot can a Christmas tree get?
The Particle Model, Temperature & Thermal EnergyTopic 3
The Particle Model
This describes the tiny parts that make up matter: All things are made up of tiny particles,
too small to be seen These particles are always in motion These particles have space between
them
States of Matter
There are three main states of matter: Solid Liquid Gas
There is a forth state of matter that is less common: Plasma
States of Matter
States of Matter
States of Matter: Solids
Solids substances hold their shape
The particles are very close together
The particles vibrate in place
Solids
States of Matter: Liquid
Liquids are fluids that take the shape of their container
The particles are spread apart
They move past each other
Liquids
States of Matter: Gas
Gases are fluids that fill their container
The particles have a lot of space between them
The particles move very fast
Gases
States of Matter: Plasma
Plasma is a state where the energy in the particles is so high that they break into the parts that make them up.
They are moving so fast they give off light
States of matter
Energy
Energy is not a substance It cannot be seen, weighed or take
up space Energy is a condition or quality that
a substance has Energy is a property or quality of an
object or substance that gives it the ability to move, do work or cause change.
Energy
Energy is the measure of a substances ability to do work or cause change Changes happen when
there is a difference of energy
Energy is always transferred in the same direction: from high-energy (hot) to low-energy (cold)
Think About it!
Is the energy transferred from the ice to the drink, or the drink to the ice?
Energy
There are seven different forms of energy
The Law of Conservation of Energy
Energy cannot be created or destroyed
Energy can only be transformed from one type to another, or passed from one object, or substance, to another
Thermal Energy & Temperature Change
Temperature is the average energy of the particles
When heat is transferred the temperature is affected by increasing or decreasing
The temperature depends on the number of particles affected What does that mean?
Expansion & ContractionTopic 4
Expansion & Contraction
As the average energy (temperature) of particles changes, the spaces between the particles change
Particles expand - increase volume - as they are heated
Particles contract - decrease volume - as they are cooled
Expansion &Contraction
Pure substances are matter made of only one type of particle, either solid, liquid or gas
Solids Liquids Gases
Shape & Size
Keep their shape and
size
Take the shape of
their container
No definite shape or size
Compressibility
(volume)
Cannot be compressed
(fixed volume)
Almost incompressib
le(fixed
volume)
Can be compressed
(volume changes)
Expansion & Contraction Solids
Solids can become longer and shorter depending on temperature
The particles stay in place but vibrate faster, spreading them apart.
Think About it! What do you expect to happen?
Expansion & ContractionSolids
Expansion & Contraction Liquids
As liquids are heated the particles expand and as they cool, contract
Liquid in a thermometerdemonstrates this effectively
Expansion & ContractionGases
Particles that are heated increase space greatly Particles can also contract significantly when
they are cooled The space between particles in gases are the
most affected by changes in temperature Expansion and Contraction
Spangler Effect
How can you use expansion or contraction to get a hard boiled egg into a bottle, or to crush an empty pop can?
Egg in a Bottle Can Crusher
The Particle Model &Changes of StateTopic 5
Heat Capacity
Capacity the ability to receive or contain: This
hotel has a large capacity. the maximum amount or number that
can be received or contained; cubic contents; volume: The inn is filled to capacity. The gasoline tank has a capacity of 20 gallons.
Heat Capacity
The amount of thermal energy (heat) that warms or cools an object by 1˚C
It describes a particular object
It depends on the mass of an object and the material it is made of
Heat Capacity
Specific Heat Capacity
The amount of thermal energy (heat) that warms or cools 1g of a material by 1˚C
It describes a specific material
It depends only on the material the object is made of
Specific Heat Capacity
Specific Heat Capacity
Heat Capacity
Think About it!
Do you think it is possible to boil water in a plastic bag?
Survival 101
Changes of State
As particles speed up and slow down, they will change state after a certain point
Solid Liquid Gas Ice Water Steam
Changes of State
freezing
Changes of State
Different substances require different temperatures or amounts of pressure to change state
Changes of state are reversible under the right conditions Baking a liquid batter into a solid cake is
not a change of state, it cannot be reversed
HOMEWORK!
What is the difference between evaporation and boiling?
Melting & Boiling
When energy is added to a substance the particles speed up
Melting is a solid to a liquid Ice to water
Boiling or Evaporation is a liquid to a gas Water to steam The Leidenfrost Effect
Melting & Boiling
All pure substances have melting and boiling points (p.221) Many substances have combustion
points that prevent melting – like wood Most substances are gases or solids
at regular atmospheric temperatures Many substances are not stable in liquid
state
Melting & Boiling Points
Condensation & Freezing
When energy is removed from a substance the particles slow down
Condensation is a gas to a liquid Drops of water forming on the outside of
a cold glassFreezing is a liquid to a solid
Water to ice
Sublimation & Deposition
When a substance is unstable as a liquid it may change state from solid to gas and gas to solid
A solid to gas is Sublimation Dry Ice to gas
A gas to a solid is Deposition Water vapor to frost on a window
Liquids
Particles in liquids move very quickly
As high energy particles escape the liquid, the average energy decreases, cooling the liquid
Liquids
Evaporation cools the surface the liquid is on
This process is called evaporative cooling
Evaporative cooling is useful for: Joggers cooling as sweat evaporates Water cooling a roof on a hot day A wet cloth on a forehead for a fever KangaroosBUT: Hypothermia can happen because of it!
Transferring EnergyTopic 6
Energy Transfer
Energy can be transferred 3 ways: Radiation Conduction Convection
BY SONG!
Radiation
This is the transfer of energy without the movement of particles
This is also called Electromagnetic Radiation (EMR)
Radiant energy travels in waves
It can pass throughspace, air, glass and many other materials
Radiation – EMR Spectrum
Radiation
All radiant waves travel very fast across empty space – at 300million m/s
Radiant energy travels in a straight line
Most radiation that we are exposed to is natural.
Radiation (the radioactivity) can be detected, measured and controlled
Radiation
Light waves and radiation waves will travel until they hit something that will: Absorb▪ Let the radiation get part way into an object,
often as heat Transmit ▪ Allow the radiation to pass through, without
absorption Reflect▪ Cause the radiation to bounce off
Radiation - Absorbtion
Dark coloured surfaces: absorb radiant energy
when they are cool give off radiant energy
when they are hot Light coloured or shiny
surfaces do not effectively absorb or give off radiant energy
Can you think of animals adapted with this in mind?
Radiation - Absorbtion
•Radiant emission (giving off) of energy depends on surface area▫Animal adaptations show this:
Desert animals have large ears to release heat
Killer whales have simple bodies and small limbs to keep heat in
Polar bear has black skin to absorb radiant energy with transparent hair that transmits ultraviolet radiation to the skin
Conduction
Conduction is the transfer of energy through solids
Direct collisions between particles pass energy through the objects
The space between particles in a solid determines how fast energy is conducted
Conduction
Metal particles are often very close together, they conduct well
Wood, plastic and glass particles are further apart and are poor conductors – called insulators
A metal wire will conduct, but is wrapped in plastic to insulate it
Convection
The transfer of energy in fluids It follows a circular pattern called a
convection current As fluid particle heat up, speed up,
and spread apart, they become lighter and rise
Once further from the heat, the particles cool and fall
Convection
Convection in the atmosphere causes thermals which birds and gliders use to soar, they also cause turbulence on planes
Convection ovens cook more evenly by circulating heat
Convection Currents
Convection Currents
REMEMBER:
Energy can be transferred 3 ways: Radiation Conduction Convection BY SONG!
Heat energy always flows from the warmer to cooler object or substance
Think About it!Conservation of Energy
Energy cannot be created or destroyed
Energy can only be transformed from one type to another, or passed from one object, or substance, to another
Turn to p.232: follow the transfer of energy
Energy Transfer
Energy in her fist transferred to the ball The ball transferred energy to the floor. Conduction occurred, when the energy in her fist
was conducted by the particles in her fist to the particles in the ball.
The particles in the ball conducted the energy to the particles in the floor.
The particles in the air were also warmed by the flight of the ball and the particles transferred this energy by convection currents which were created in the air.CREATE AN ENERGY FLOW SYSTEM
Energy Systems
All Energy Systems have 5 features:1. Energy Source
Energy can be mechanical, chemical, radiant, nuclear or electrical
2. Direction of Energy Transfer Energy moves from high to low concentration
3. Transformations Energy changes form as it is transferred
4. Waste Heat Most energy is transferred, but some is always lost
to surroundings5. Control Systems
A device to start and stop the transfer of energy
Sources of Thermal EnergyTopic 7
Sources of Thermal Energy
Energy is often converted before we can use it
Many sources come with environmental concerns
Sources of Thermal Energy
Mechanical Chemical – burning fuel Electrical – generators Nuclear Wind Geothermal Solar
Fossil Fuels
Mechanical Energy
Generation of Electric Energy
1. Fuel is burned to produce heat2. Heat is transferred to water to produce steam3. Steam is channeled4. Steam used to turn turbine which in turn cranks
the generator
Generation of Electric Energy
Chemical Energy
Chemical energy can be transformed into thermal energy when wood or coal is burned
Impact: Pollution is caused by the release of greenhouse gases when fossil fuels are burned
Coal
Sheerness Thermal Generating Station – Hanna
Hydro-Electric Energy
Gravity is used to pull water over dams to turn turbines, attached to generators
Mechanical energy of the generators creates electricity
Hydro-Electric Energy
Impact: Habitats are affected, heated waste water is produced and ecosystems are reshaped
Nuclear Energy
Pickering Nuclear Power Plant
Wind Energy
Wind turbines spin from the force of the wind, powering a generator
Wind Energy
Impact: the spinning turbines create areas of low pressure, when bats enter the pocket, the low pressure causes their lungs to explode
Wind Energy
Wind Energy - Canada
Geothermal Energy
Geo – to do with the earth Thermal – related to heat
Volcanoes, hot springs and geysers are sources of geothermal energy
This heat creates steam which is harnessed in power plants on the surface
Geothermal vs. other sources
Geothermal Energy
HDR (Hot, dry rock) is another technique – water is pumped down, heated and resurfaces as steam, which is used to generate power
Geothermal Energy
This is a clean and environmentally friendly technique
It could reduce the threat of oils spills, pollution from fossil fuels and their wastes
The initial cost of installing geothermal is still quite high.
Solar Energy
Solar Energy
Solar energy is clean and unlimited
There are two ways to use solar power:
1. Passive Solar Heating – uses the materials in the structure to absorb, store and release solar energy
2. Active Solar Heating – uses mechanical devices to collect and distribute the thermal energy
Solar Energy – Passive
Solar Energy – Active
Solar Energy
Fossil Fuels
Fossil Fuels
Big Problems: Non-renewable Greenhouse
gases contributing to global warming
Fossil Fuels – Cogeneration
This uses about 2/3 fossil fuel, and released thermal energy is put to use as well
Other Energy Sources
Organisms burn food to generate body heat
Composts are a source of thermal energy – Decomposers break down food and release thermal energy, speeding up decomposition (waste management)
Turkey power! Internal Combustion Engine
Think About it!
What else could be used as an energy source?
Alberta’s Energy
Conserving Our Fossil Fuel ResourcesTopic 8
Introduction
We still use many fossil fuels: Coal is burned Oil and gas are used
How can we reduce our use? Technology gives us ways to use energy
more responsibly.
Programmable Thermostats
Hot Water on Demandp.252
Thermal Energy Movers
Thermal energy movers transfer thermal energy from one location to another at a different temperature• Fridges and air conditioners
The operation of these devices requires refrigerants to remove thermal energy from food.
Thermal Energy Movers
As the refrigerant evaporates, it absorbs the thermal energy from the food so it cools down.
This warmed gas is then compressed and releases the thermal energy into the room.
Deconstructed: Fridge
Thermal Energy Risks
Some harmful effects of thermal energy are: burning ourselves on a hot utensil (us) forest fires (our environment) burning houses (our belongings) What are some other negative effects of
thermal energy use?
Thermal Energy By-products Not all the dangers of using thermal energy
are as obvious as the ones already discussed. Sulfur-dioxide is
released when coal and natural gas are burned.
This gas is an irritant to the eyes, nose and throat.
It contributes to the production of Acid Rain
Thermal Energy By-products
Carbon monoxide is produced when a fire burns without enough oxygen.
It is colorless and odorless. Hinders brain reasoning and is lethal
Smoke detectors and CO detectors should be installed in every buildingto protect the people from being overcome by these lethal gases.
Thermal Energy By-products
Carbon dioxide that is released from the burning of fossil fuels is a greenhouse gas, which traps heat energy in our atmosphere and leads to global warming
THE END!
Make sure your vocabulary and topic questions are complete!
Go through the questions at the front of your book to make sure you understand everything
Study from your quizzes and notes Go online and use your text for
review
Recommended