Presentation on theme: "Boardworks GCSE Science: Physics Heat Loss and Insulation"— Presentation transcript:
1 Boardworks GCSE Science: Physics Heat Loss and Insulation
2 Boardworks GCSE Science: Physics Heat Loss and Insulation
3 Boardworks GCSE Science: Physics Heat Loss and Insulation A temperature problemBoardworks GCSE Science: PhysicsHeat Loss and InsulationTouch a piece of metal and a piece of wood at the same temperature. Which material feels warmer and why?The metal feels cold and the wood feels warm.Metal is a good conductor and conducts the heat away from your hands, so it feels cold.Teacher notesStudent could be asked to try this experiment if the materials are available.Wood is not a good conductor and does not conduct the heat away from your hands as well as the metal, so thewood feels warmer than the metal.
4 What are thermal insulators? Boardworks GCSE Science: PhysicsHeat Loss and InsulationSome materials are very poor conductors of heat. These are called thermal insulators.Examples of materials that are insulators include plastics, wood, ceramics and air.Air becomes a very effective insulator when it is trapped and stopped from moving.This is how your clothes keep you warm – air is trapped between the fibres and so acts as an insulator.Other insulating materials, including polystyrene and loft insulation, use trapped air because it is so effective.
5 Charlie the Chef and his frozen chicken! Boardworks GCSE Science: PhysicsHeat Loss and InsulationCharlie forgot to take the chicken out of the freezer last night!Will his plan to defrost the chicken in time for lunch work?Teacher notesThe illustration could be used to develop students’ understanding of the relationship between heat loss and insulation.Left: It is am and Charlie, our forgetful, rosy-cheeked, woolly-jumper-wearing chef, is staring at a very frozen chicken, which needs to be ready for lunch. What can he do to speed up the defrosting process?Right: Five minutes later in the same kitchen and Charlie has transferred his woolly jumper to the frozen chicken, mistakenly convinced that this will warm up the chicken and help to defrost it!These illustrations can be used to tackle the common misconception that insulation makes an object warm and explain that insulation actually prevents heat transfer between an object and its surroundings, so Charlie’s plan is destined for failure. Students could be given coloured traffic light cards and asked to vote on whether Charlie’s plan will be a success. The activity could be extend by asking students to explain their voting.
6 How does a vacuum flask work? Boardworks GCSE Science: PhysicsHeat Loss and InsulationHow is a vacuum flask able to keep hot drinks hot and cold drinks cold?2. The plastic (or cork) lid is an insulator and the screw top prevents convection currents escaping from the flask.1. There is a vacuum between two layers of glass or steel, which prevents heat leaving or entering by conduction.3. The walls have silvery surfaces, which prevent heat leaving or entering by radiation.`
7 Boardworks GCSE Science: Physics Heat Loss and Insulation
8 Boardworks GCSE Science: Physics Heat Loss and Insulation Heat loss from housesBoardworks GCSE Science: PhysicsHeat Loss and InsulationA thermogram shows the distribution of heat over the surface of a house. It highlights where heat is being lost.The white, yellow andred areas are the warmest, so these arethe worst insulatedparts of the house.The blue and green areas are the coolest, so these are the best insulated parts of the house.Photo credit: Alfred Pasieka / Science Photo LibraryThermogram of a house showing the distribution of heat over its surface. The colour coding ranges from white to yellow for the warmest areas (greatest heat loss) through red to purple and green for the coolest areas (greatest insulation). This thermogram shows that the roof and windows (yellow) are poorly insulated, while the walls (red, purple and green) are losing the least heat. Thermograms are often used to check houses for heat loss, so that they can be made more energy efficient through improved insulation.A poorly insulated house loses more energy and so costs more to heat. It also means that more pollution, particularlycarbon dioxide, is created in order to heat the house.
9 Boardworks GCSE Science: Physics Heat Loss and Insulation Heat loss from housesBoardworks GCSE Science: PhysicsHeat Loss and InsulationWhere is the most heat lost from a poorly insulated house?roof 20%windows 12%Teacher notesIt should be stressed that these values are for an average poorly insulated house.walls 36%doors 4%floor 28%
10 How can heat loss be reduced? Boardworks GCSE Science: PhysicsHeat Loss and InsulationVarious types of insulation can prevent the loss of heat energy from a house.Use the following slides to complete this table showing how different types of insulation can prevent loss of heat energy from a house.Type of insulationType of heat transfer stoppedHow insulation stops heat transfer
11 Can heat loss through windows be reduced? Boardworks GCSE Science: PhysicsHeat Loss and InsulationA lot of heat energy can be lost through windows.Double glazing adds an extra pane of glass. The air trapped between the two panes acts as an insulator and reducesheat loss by conduction.insulating layerof airside-viewof double glazingThe insulating effect of the gap can be improved by removing the air and creating a vacuum.Teacher notesThis slide could be used to start a discussion about the advantages and disadvantages of double glazing and how it’s use is compulsory when building new houses. Triple glazing could also be discussed. It offers better insulation against heat loss than double glazing, but this saving does not cover the extra cost of installing triple glazing. However, triple glazing offers additional benefits, such as improved noise insulation.The problems with double glazing are that it can be expensive and that it is difficult to break in emergencies without a special hammer.
12 How can heat loss through walls be reduced? Boardworks GCSE Science: PhysicsHeat Loss and InsulationMost outside walls have an empty space between the two layers of bricks called a cavity.convection currentsin the cavityThe air trapped in the cavity acts as an insulator and reduces any heat loss due to conduction through the bricks.Heat loss can also occur due to convection within the cavity. Plastic foam insulation can be pumped into the cavity to prevent this.foam insulationprevents convection currentsTeacher notesIt should be highlighted to students that older brick and stone buildings do not have cavity walls. It can be expensive to fit cavity wall insulation to old buildings but it is easy to add to new buildings.
13 How can heat loss through a roof be reduced? Boardworks GCSE Science: PhysicsHeat Loss and InsulationThe air warmed by radiators (and other heaters) is carried around a house by convection currents.heat lossThe house becomes heated but,if there is no roof insulation, the warm air continues to rise.The heat eventually escapes through the roof and is lost due to conduction through the roof tiles.loft insulationLoft insulation contains trapped air and so forms an insulating layer between the loft and the rest of the house. This helps to reduce heatloss through the roof.
14 How can heat loss from radiators be reduced? Boardworks GCSE Science: PhysicsHeat Loss and InsulationA radiator produces infrared radiation.Some of this heat energy is absorbed by the wall that the radiator is attached to, and so the wall heats up.This can be a real problem on outside walls, where the heat energy absorbed by the wall can escape from the house.Heat loss from a radiator can be reduced by placing shiny foil between the wall and the radiator.The foil prevents heat radiation from reaching the wall by reflecting it back into the room.This method of insulation is very cheap to install.
15 How can heat loss through doors be reduced? Boardworks GCSE Science: PhysicsHeat Loss and InsulationA draught is the movement of air due to a convection current.A lot of heat energy can be lost from a house due to draughts escaping through gaps under doors and around windows.This is one of the easiest types of heat loss to prevent.Draught excluders are hairy or spongy strips that can be used to close the gaps around doors and windows.They prevent draughts escaping and so reduce heat loss.
16 How can curtains reduce heat loss? Boardworks GCSE Science: PhysicsHeat Loss and InsulationA draught is the movement of air due to a convection current.Warm air rises and is carried up towards the windows in a house by convection currents.This heat energy can escape through gaps around windows that are uncovered.Fitting curtains and closing them can prevent draughts leaving a house and so reduce heat loss.In addition, curtains are opaque and so radiated heat does not pass through them.
17 How does insulation affect heat loss? Boardworks GCSE Science: PhysicsHeat Loss and InsulationTeacher notesThis activity could be used to show the effect of insulation on the fuel bill for a poorly insulated house. Changes to the insulation can be made individually or in combination, allowing students to investigate the effect of several simple insulation methods.
18 Insulation and heat loss – true or false? Boardworks GCSE Science: PhysicsHeat Loss and InsulationTeacher notesThis true-or-false activity could be used as a plenary or revision exercise on insulation and heat loss. It could also be used at the start of the lesson to gauge students’ existing knowledge of this subject matter. Coloured traffic light cards (red=false, yellow=don’t know, green=true) could be used to make this a whole-class exercise.
19 How does double glazing work? Boardworks GCSE Science: PhysicsHeat Loss and InsulationHow does double glazing keep a house warmer?Double glazing keeps a house warmer because there is a layer of a__ between the panes of glass.irAir is a poor c________,so it acts as an i_______.onductornsulatorThe trapped air r_______ heat loss by c_________ from a house.educesonductionside-viewof double glazing
20 Insulation and heat transfer Boardworks GCSE Science: PhysicsHeat Loss and InsulationTeacher notesThis classification activity provides the opportunity for some informal assessment. Coloured traffic light cards (green=conduction, yellow=convection, red=radiation) could be used with this activity to increase class participation.
21 Boardworks GCSE Science: Physics Heat Loss and Insulation
22 Boardworks GCSE Science: Physics Heat Loss and Insulation What is payback time?Boardworks GCSE Science: PhysicsHeat Loss and InsulationPayback time is the time it takes for the cost of installing insulation to be equalled by the savings made from reduced energy costs.payback time (in years) =cost of insulationsaving each yearExample:Adding silver reflectors behind radiators costs £25 and saves £50 per year.Teacher notesIt should be highlighted that the payback time is measured in years and that the shorter the payback time, the quicker fuel bill savings will pay for the cost of installing the insulation.payback time = 2550= 0.5 years (6 months)
23 Calculating payback time Boardworks GCSE Science: PhysicsHeat Loss and InsulationWhat is the payback time for these types of insulation?How heat escapesCost of heat escapingper yearCost of insulationPayback timeroofwindowsdraughtswalls£80£40£50£100£240£3,200£50£5003 years80 years1 year5 yearsWhy is double glazing popular if the payback time is so long?
24 Which insulation is most cost-effective? Boardworks GCSE Science: PhysicsHeat Loss and InsulationCost-effectiveness is a comparison of the annual savings in reduced energy bills and the cost of insulation.Cost-effectiveness =saving each yearcost of insulationExample 1:Example 2:Adding silver reflectors behind radiators costs £25 and saves £50 per year.Adding draught excluders costs £50 and saves £50 per year.Teacher notesCalculating cost effectiveness is an alternative to calculating payback times and allows different types of insulation methods to be compared. It should be made clear that insulation types with larger cost-effectiveness factor values are more cost-effective than insulation types with smaller values.Cost-effectiveness = 50/25Cost-effectiveness = 50/50= 2= 1So, the reflectors are more cost-effective than the draught excluders.
25 Calculating cost-effectiveness Boardworks GCSE Science: PhysicsHeat Loss and InsulationTeacher notesThis ordering activity could be used as a plenary or revision exercise. Mini-whiteboards could be used to make this a whole-class exercise.
26 Boardworks GCSE Science: Physics Heat Loss and Insulation
27 Boardworks GCSE Science: Physics Heat Loss and Insulation Glossary (1/2)Boardworks GCSE Science: PhysicsHeat Loss and Insulationcavity wall – A wall made up of two layers of bricks with an air gap between them, which reduces heat lost by conduction.cavity wall insulation – Plastic foam insulation that is pumped into the gap in a cavity wall to prevent heat lost dueto convection in the cavity.cost-effectiveness – A comparison of the annual savings in reduced energy bills and the cost of insulation.double glazing – Two panes of glass with an air gap between them, which reduces heat lost by conduction. Theair can be sucked out of the gap to create a vacuum.draught excluder – A hairy or spongy strip thatprevents draughts escaping through the gaps around doors and windows, and so reduces heat loss.
28 Boardworks GCSE Science: Physics Heat Loss and Insulation Glossary (2/2)Boardworks GCSE Science: PhysicsHeat Loss and Insulationloft insulation – A material which contains trapped air and helps to reduce heat lost through the roof of a house.insulator – A material that is a very poor conductor of heat and so can be used to reduce heat loss.payback time – The time it takes for the cost of insulation to be equalled by the savings from reduced energy bills.vacuum flask – A vacuum flask is a bottle with double walls separated by a vacuum. It reduces heat transfer andso keeps warm drinks warm and cold drinks cold.
29 Boardworks GCSE Science: Physics Heat Loss and Insulation AnagramsBoardworks GCSE Science: PhysicsHeat Loss and Insulation
30 Boardworks GCSE Science: Physics Heat Loss and Insulation Multiple-choice quizBoardworks GCSE Science: PhysicsHeat Loss and InsulationTeacher notesThis multiple-choice quiz could be used to assess students understanding of heat loss and insulation. The questions can be skipped through without answering by clicking “next”. Students could be asked to complete the questions in their books and the activity could be concluded by the completion on the IWB.