P1 – Energy for the home Revision lesson 1. 15/04/2015 Revision Lessons Does not contain all of...
-
Upload
cassie-jefcoat -
Category
Documents
-
view
213 -
download
0
Transcript of P1 – Energy for the home Revision lesson 1. 15/04/2015 Revision Lessons Does not contain all of...
18/04/2318/04/23
Revision LessonsRevision LessonsDoes not contain all of the content for P1 – use Does not contain all of the content for P1 – use checklistschecklists
..\P1 Energy for the home 2011\Summary and ..\P1 Energy for the home 2011\Summary and Checklists\P1 Checklist Foundation.docChecklists\P1 Checklist Foundation.doc..\P1 Energy for the home 2011\Summary and ..\P1 Energy for the home 2011\Summary and Checklists\P1 Checklist Higher.docChecklists\P1 Checklist Higher.doc
Temperature and heatTemperature and heat
TemperatureTemperature is a measurement of is a measurement of hotnesshotness..
The temperature of an object is The temperature of an object is measured in degrees celsius measured in degrees celsius ((°C).°C).
HeatHeat is a measurement of the is a measurement of the energyenergy of an objectof an object
Heat energy is measured in Joules Heat energy is measured in Joules (J)(J)
CompleteComplete cool high higher low quicker thermograms cool high higher low quicker thermograms
warm warm coldcold warmwarm Hot objects have a __________ temperature and usually Hot objects have a __________ temperature and usually
__________ down.__________ down. Cold objects have a __________temperature and usually Cold objects have a __________temperature and usually
__________ up.__________ up. Energy will flow from a hotter object to a colder one.Energy will flow from a hotter object to a colder one. The greater the temperature difference, the faster the rate The greater the temperature difference, the faster the rate
of cooling will be. For eg. A hot cup of coffee would cool of cooling will be. For eg. A hot cup of coffee would cool down faster in a _______room than in a ______ roomdown faster in a _______room than in a ______ room
____________________ are pictures in which colour is used to ____________________ are pictures in which colour is used to represent temperature.represent temperature.
For warm objects, the __________ the temperature, the For warm objects, the __________ the temperature, the __________ they cool.__________ they cool.
Specific heat capacitySpecific heat capacity The amount of energy needed to raise the temperature of somethingThe amount of energy needed to raise the temperature of something depends depends
on:on:
How much there is (mass)How much there is (mass)
The temperature riseThe temperature rise
What it is (specific heat capacity)What it is (specific heat capacity)
EnergyEnergy = = mass mass x x specific heat capacityspecific heat capacity x x temperature change temperature change
Calculate the energy transferred when 80kg of water is heated from 10oC to 25oC.Calculate the energy transferred when 80kg of water is heated from 10oC to 25oC.
80 x 4200 x (25-10) = 5 040 000 J80 x 4200 x (25-10) = 5 040 000 J
SHC = how much energy something can store. The specific heat capacity of water SHC = how much energy something can store. The specific heat capacity of water is high therefore is high therefore once heated once heated it stores alot of energy, so its used for central it stores alot of energy, so its used for central heatingheating
Remember water has a higher SHC than most things so it can take more heat Remember water has a higher SHC than most things so it can take more heat energy (time) to increase its temperatureenergy (time) to increase its temperature
Specific latent heatSpecific latent heatSpecific latent heat is the energy needed to Specific latent heat is the energy needed to change change the state the state of 1kg of a substance without changing its of 1kg of a substance without changing its temperaturetemperature
Specific latent heat water to stem Specific latent heat water to stem
= 2 260 000 j/kg= 2 260 000 j/kg
Energy = mass x specific latent heatEnergy = mass x specific latent heat
Calculate the energy transferred when 1.5kg of water in Calculate the energy transferred when 1.5kg of water in a kettle changes from liquid to a gas at 100oC.a kettle changes from liquid to a gas at 100oC.
1.5 x 2 260 000 = 3 390 000J1.5 x 2 260 000 = 3 390 000J
Energy needed to change state, its different for all Energy needed to change state, its different for all different materialsdifferent materials
EnergyMass x SLH
Time/s
150
100
50
0
-50
heating
Meltingpoint
Boiling point
heating
solid
liquid
gas
This flat line shows where energy is being used to break the intermolecular bonds for evaporation
This flat line shows where energy is being used to break bonds – this has to be done during melting
Energy is put into break intermolecular bonds
Heat transferHeat transfer
Heat can transfer in one of three Heat can transfer in one of three ways:ways:
ConductionConduction Convection Convection RadiationRadiation
Conduction is all about when heat is transferred through a _________. The heat is passed on by ___________ in the molecules. These vibrations get BIGGER when the solid has more ENERGY (i.e. when it is being __________).
Metals are _______ conductors than non-metals. This is because the heat is carried by free ________ that can carry the energy around the metal and give it to other electrons and ions.
ConductionConduction
Words – vibrations, electrons, solid, heated, better
Heating a non-metal
Heating a metal
How does a cavity wall prevent heat loss from a home?1. H____ energy reaches the interior wall
2. The heat energy is c_______ through the wall
3. The air cavity between the two walls acts as an i_______ and reduces heat loss by c_______ .
Cavity WallsCavity Walls
ConductionConduction
eat
onducted
nsulatoronducti
on
© Boardworks Ltd 200511 of 31
Side-view of double glazing
insulating layer of air
Double glazing keeps a house warmer because there is a layer of a__ between the panes of glass.
Air is a poor c________, so it acts like an i_______, .
The trapped air r_______ heat loss by c_________ from a house.
ir
onductornsulator
educesonduction
Double glazing
How does double glazing keep a house warmer?
Convection – Key IdeasConvection – Key Ideas
Heat transfer through liquids and Heat transfer through liquids and gasesgases
Heat causes particles in a fluid to: Heat causes particles in a fluid to: move apart move apart → less dense → lighter → less dense → lighter → rises (and replace by cooler → rises (and replace by cooler fluid)fluid)
Insert the Missing WordsInsert the Missing Words
heat1. As the water is ______ it becomes
less dense and _____
2. On reaching the surface, the water _____
when in contact with the air
3. As the water cools it becomes more ______ and
sinks
4. A cycle develops whereby warm water rises and cool water sinks, we call this a
__________ current
heated rises
cools
dense
convection
ConvectiConvectionon
Radiation – key factsRadiation – key facts
All hot objects radiate heat.All hot objects radiate heat. Called infra-red radiationCalled infra-red radiation Dull, dark surfaces are the best Dull, dark surfaces are the best
radiators and absorbers of heatradiators and absorbers of heat Pale, shiny surfaces are the worst Pale, shiny surfaces are the worst
radiators and absorbers of heatradiators and absorbers of heat Infra–red radiation can travel Infra–red radiation can travel
through a vacuumthrough a vacuum
18/04/23
Radiation is when heat moves around in electromagnetic _________ like light does. Any hot object will emit heat radiation – the hotter it is, the more radiation it emits. This type of radiation is called __________, and too much of it will cause _________. Dark, matt colours will absorb AND emit the _____ infra-red radiation, and light, shiny colours will ________ it.
The main difference with radiation is that conduction and convection could ONLY happen in solids, liquids or gases, whereas radiation will happen through an _____ _____. This is just as well, as otherwise we wouldn’t be able to get any heat from the ___.
RadiationRadiation
Words – sun, reflect, infra-red, waves, most, empty space, sunburn
Anything HOT emits HEAT RADIATION – the hotter it is, the more infra red radiation it emits
Thought shower: Where can heat be lost from your home?:
Obviously, insulating your home can be quite expensive.
Reduce energy loss from Reduce energy loss from homeshomesRoof - insulate loft; reduce conduction
through ceiling and convection in loft space •
Walls - cavity wall insulation; reduce conduction, convection, radiation (if shiny)
Windows - double glazing; reduce conduction, convection if vacuum or gas at low pressure
Doors - draught excluder; reduce conduction, convection
Floors - carpets; trapped air pockets in wool are good insulators they reduce conduction
Home insulationHome insulation
We can reduce the heat losses from our homes in We can reduce the heat losses from our homes in many ways. Unscramble the list below to find out the many ways. Unscramble the list below to find out the ways:ways:
bouled zgnlagibouled zgnlagivytiac llaw sunatoinilvytiac llaw sunatoinilDrghaut xluecderDrghaut xluecderfotl sunatoinilfotl sunatoinilarcetpsarcetpsurctansiurctansi
Why do each of these methods work? Why do each of these methods work? Describe which method of heat transfer they reduceDescribe which method of heat transfer they reduce
6 marker question6 marker question
Energy losses in the home can be reduced by energy saving measures. One measure is to have double-glazed windows which reduce the amount of heat lost by conduction. The gap between the two pieces of glass is usually filled with a gas or a vacuum
Describe how energy is lost through the wall from the inside to the outside and how the insulation reduces the different types of energy loss. ! The quality of written communication will be assessed in your answer to this question. Describe how energy is lost through the wall from the inside to the outside and how the insulation reduces the different types of energy loss. ! The quality of written communication will be assessed in your answer to this question.
Describe how energy is lost through the wall from the inside to the outside and how the insulation reduces the different types of energy loss. ! The quality of written communication will be assessed in your answer to this question
Payback and EfficiencyPayback and Efficiency Payback time is the time it takes for Payback time is the time it takes for
an insulation to pay for itselfan insulation to pay for itself Payback time = Payback time = Cost of improvementCost of improvement
saving per saving per yearyear
Efficiency = Efficiency = useful energy outuseful energy out
total energy intotal energy in
e
output
input
Payback and Efficiency Payback and Efficiency questionsquestions
1.1. Dan spends £120 on loft insulation. He is told that this will Dan spends £120 on loft insulation. He is told that this will reduce his bill by £40 per year. Calculate the payback time.reduce his bill by £40 per year. Calculate the payback time.
2.2. What is payback time?What is payback time?
2.2. Dan heats his house with coal fires. He is told that his fires are Dan heats his house with coal fires. He is told that his fires are 32% efficient. Explain what this means.32% efficient. Explain what this means.
3.3. A kettle gives out 80J of heat to the room, and is supplied with A kettle gives out 80J of heat to the room, and is supplied with 180 J of energy. How efficient is the kettle?180 J of energy. How efficient is the kettle?
4.4. 120/40 = 3years120/40 = 3years
5.5. How long it will take the cost of the item to start saving on How long it will take the cost of the item to start saving on energy bills .Its the cost of insulation divided by annual saving. energy bills .Its the cost of insulation divided by annual saving.
3. How much useful energy is supplied from a device3. How much useful energy is supplied from a device
4. 180-80 = useful = 100J4. 180-80 = useful = 100J
100/180 = 0.56 J 100/180 = 0.56 J
Plenary - To DoPlenary - To Do
Make flash cards for:Make flash cards for:
Heat and temperatureHeat and temperature Specific heat capacity and Specific latent heatSpecific heat capacity and Specific latent heat Heat transfer (conduction, convection and Heat transfer (conduction, convection and
radiation)radiation) Reducing energy losses from the homeReducing energy losses from the home Payback and efficiencyPayback and efficiency
Now use them to test a partnerNow use them to test a partner