AQA GCSE Physics 1a1 Heat Transfer

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AQA GCSE Physics 1a-1Heat Transfer

• GCSE Physics pages 24 to 37

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AQA GCSE Specification

• HEAT ENERGY TRANSFER
• 11.1 How is heat (thermal energy) transferred and
  what factors affect the rate at which heat is
  transferred
• Using skills, knowledge and understanding of how
  science works
• to evaluate ways in which heat is transferred
  in and out of bodies and ways in which the rates
  of these transfers can be reduced.
• Skills, knowledge and understanding of how
  science works set in the context of
• Thermal (infra red) radiation is the transfer
  of energy by electromagnetic waves.
• All bodies emit and absorb thermal radiation.
• The hotter a body is the more energy it
  radiates.
• Dark, matt surfaces are good absorbers and
  good emitters of radiation.
• Light, shiny surfaces are poor absorbers and
  poor emitters of radiation.
• The transfer of energy by conduction and
  convection involves particles and how this
  transfer takes place.
• Under similar conditions different materials
  transfer heat at different rates.
• The shape and dimensions of a body affect the
  rate at which it transfers heat.
• The bigger the temperature difference between
  a body and its surroundings, the faster the rate
  at which heat is transferred.

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Thermal radiationNotes questions from pages 24
25

• Draw figure 1 on page 24 and describe the
  experiment.
• Why is thermal radiation sometimes called
  infra-red radiation?
• Copy the Key points on page 25.
• In what form does energy travel from the Sun?
• Explain what is meant by the Greenhouse Effect
• Copy and answer questions (a) and (b) on page 24.
• Copy the Key Points on page 25.
• Answer the summary questions on page 25.

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Thermal radiation ANSWERS

• In text questions
• The water is cooler than the rhino, so there is
  less radiation from it.
• The radiation from the rhino reflects at the
  water surface so the water surface acts like a
  mirror.

• Summary questions
• Hot iron infra-red only
• light bulb both
• TV screen light only
• Sun both
• Put your hand near it and see if it gets warm due
  to radiation from the iron.
• (a) They lose less heat through radiation when
  they huddle together because they radiate heat to
  each other.
• (b) Is your design a fair test?

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Surfaces and radiationNotes questions from pages
26 27

• Which surfaces are (a) the best emitters (b)
  the best absorbers (c) the worst emitters (d)
  the best reflectors of radiation.
• Draw diagrams to explain why rough surfaces
  absorb radiation better than smooth ones.
• Copy and answer questions (a) and (b) on page 26.
• Describe an experiment to compare how different
  surfaces absorb radiation.
• Copy the Key Points on page 27.
• Answer the summary questions on page 27.

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Surfaces and radiation ANSWERS

• In text questions
• A sandy surface is rough, not smooth, so it
  absorbs solar radiation more than a smooth icy
  surface. The sand grains become warm and melt the
  ice.
• They absorb solar radiation better than any other
  type of surface.

• Summary questions
• 1. (a) White buildings stay cooler than dark
  buildings, are better reflectors than dark
  buildings and they absorb less solar radiation.
• (b) A black surface absorbs solar radiation
  better than a light surface.
• 2. (a) To ensure a fair test.
• (b) (i) D (ii) B
• (c) (i) B (ii) D
• (d) Greater accuracy, collects multiple sets
  of data at whatever time intervals you choose.
• 3. In direct sunlight black will absorb heat
  readily, but in shade black will emit heat more
  readily.

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ConductionNotes questions from pages 28 29

• Describe, with the aid of a diagram, an
  experiment to compare how well materials conduct
  heat.
• Explain the process of how conduction occurs in
  (a) metals and (b) non-metals.
• Why are metals generally better conductors than
  non-metals?
• Copy and answer questions (a), (b), (c) and (d)
  on pages 28 and 29.
• Copy the Key Points on page 29.
• Answer the summary questions on page 29.

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Conduction ANSWERS

• In text questions
• Plastic and wood are poor thermal conductors, so
  the handle doesnt get hot.
• The material the rods are made from is the
  independent variable. The dependent variable is
  the time taken for the wax to melt.
• Felt.
• The starting temperature.

• Summary questions
• (a) Fibreglass (b) Wood, plastic (c) Steel
• 2. (a) Felt or synthetic fur could be used,
  because they are good insulators.
• (b) Is your plan a fair test?
• 3. The free electrons that gain kinetic energy
  diffuse through the metal quickly, passing on
  energy to the other electrons and ions in the
  metal.

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ConvectionNotes questions from pages 30 31

• Describe, with the aid of a diagram, an
  experiment to demonstrate convection in air.
• Copy Figure 3 on page 30 and explain how hot
  water travels from the boiler to the hot water
  tap.
• Copy and answer question (a) on page 30.
• Draw a diagram and explain the cause of a sea
  breeze.
• Explain how convection occurs and why it only
  occurs in fluids.
• Copy the Key Points on page 31.
• Answer the summary questions on page 31.

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Convection ANSWERS

• In text question
• The water from the taps would be cold.

• Summary questions
• 1. Rises, mixes, cools, falls.
• 2. (a) It heats it and makes it rise.
• (b) The hot air passes through the grille
  into the room.
• (c) Cold air flows in at the bottom.
• 3. Drop the crystal into the beaker of water
  through a tube. Heat gently under one corner. the
  colour rises above the point of heating, travels
  across the top and falls at the opposite side of
  the beaker (where density of cooler water is
  greater). The colour then travels across the
  bottom of the beaker to replace lower density
  warmer water that rises above the Bunsen flame.

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Heat transfer by designNotes questions from
pages 32 33

• Explain how a car engine is kept cold.
• Copy and answer questions (a) and (b) on page 32.
• Copy Figure 2 on page 32 and explain how the
  different parts of the vacuum flask reduce heat
  transfer.
• Explain four ways of reducing heat loss from a
  house.
• Copy and answer question (c) on page 33.
• Copy the Key Points on page 33.
• Answer the summary questions on page 33.

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Heat transfer by design ANSWERS

• In text questions
• To increase heat loss by radiation.
• It increases.
• (d) Cavity wall insulation does not transfer
  heat by convection, because it is a solid but air
  would.

• Summary questions
• (a) Conduction (b) Convection
• (c) Radiation
• 2. (a) A metal frame conducts heat to the
  outside plastic is a poor thermal conductor so
  it does not.
• (b) A vacuum would not transfer heat by
  convection, but air would.
• (c) Is your design a fair test?
• Plastic cap reduces convection and conduction
• double walled plastic container reduces
  conduction
• silvered surfaces reduce radiation vacuum
  stops conduction and convection.

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Hot issues Notes questions from pages 34 35

• Answer part (a) from the activity on page 34.
• Answer questions 1, 2, 3, 5, 6, and 7 on pages 34
  and 35.

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Hot issues ANSWERS

• Activity part (a)
• (i) Add cavity wall insulation to reduce heat
  loss through the walls and loft insulation to
  reduce heat loss through the roof.
• (ii) 20 years.
• Thermal energy from a deep tumour would be
  conducted to the surrounding parts and would not
  reach the surface of the body.
• Appreciation that devices can assist with a range
  of treatments but they come at a cost. Is the
  money better spent on other things?
• The hospitals may be part of a research
  programme, they could be sponsored by
  manufacturer to test the technology or they could
  be given extra money by a private benefactor or
  they could even be charging for its use.

• (a) white (b) black
• (a) non-reversible
• (b) reversible
• 7. (a) The heat from the flame could escape,
  raising the temperature of the methane so that it
  ignites.
• (b) To make sure that the gauze was not damaged.
• (c) A modern flame safety-lamp and electronic
  methanometers.

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How Science Works ANSWERS

• Minimum should be that pins on the different rods
  are all the same distance along the rod. (Better
  placed at intervals along the rods).
• For example use the same amount of Vaseline each
  time.
• The metal rods should be heated in the same way
  each time by the Bunsen (e.g. in the same part of
  the flame). The rods should also be protected
  from direct radiant energy from the Bunsens
  flame which would make the results invalid.
• Repeat procedure.

• Are there accurate labels with a simple layout?
• Bar chart categoric independent variable with a
  continuous dependent variable.
• A second person achieving the same results
  increases reliability.
• The results support the conclusion. However, the
  conclusion is invalid due to different initial
  temperatures.