## (a) The table gives information about some ways of reducing the energy consumption in a house. Which way of reducing energy consumption is most cost effective over a 10-year period? To obtain full marks you must support your answer with calculations. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (3) Method of reducing energy consumption Installation cost in £ Annual saving on energy bills in £ Fit a new hot water boiler 1800 200 Fit a solar water heater 2400 100 Fit underfloor heating 600 50 Fit thermostatic radiator valves 75 20 (b) Explain why using an energy-efficient light bulb instead of an ordinary light bulb reduces the amount of carbon dioxide emitted into the atmosphere. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (Total 5 marks) Page 1 of 21
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(a) The table gives information about some ways of reducing the energy consumption in a house.
Which way of reducing energy consumption is most cost effective over a 10-year period?
To obtain full marks you must support your answer with calculations.
(b) Explain why using an energy-efficient light bulb instead of an ordinary light bulb reduces the amount of carbon dioxide emitted into the atmosphere.
Q7. The diagram shows a type of electric immersion heater in a hot water tank. These hot water tanks are normally found in airing cupboards.
Information on the immersion heater states:
230 V 10 A
(a) Immersion heaters for hot water tanks often have a switch on them labelled bath or sink. The bath position of the switch has both parts of the immersion heater elements in the circuit. The sink position has only the short heater element in the circuit.
(i) Explain why the hot water outlet is at the top of the tank, and the cold water inlet is at the bottom of the tank.
(b) A shiny metal can and a dull black can are filled with the same amounts of cold water. A radiant heater is placed exactly half way between the cans as shown in the diagram below.
Two thermometers are used to measure the temperature of the water in each can every minute.
(i) Suggest how the temperature of the water in the dull can would be different from the temperature of the water in the shiny can after ten minutes.
Q10. The diagram shows four identical pieces of aluminium. Each had been painted with a different type of paint. A drop of water was placed on each and they were then heated by a radiant heater held about one metre above them.
(i) Suggest in which order the pieces of aluminium would become dry.
first ..................... .................... ...................... ................... last (1)
200 × 10 – 1800 = £200 100 × 10 – 2400 = –£1400 50 × 10 – 600 = –£100 20 × 10 – 75 = 125 accept four final answers only or obvious rejection of solar water heater and underfloor heating, with other two calculations completed any 1 complete calculation correctly shown or showing each saving × 10 of all four calculations = 1 mark answers in terms of savings as a percentage of installation cost may score savings mark only
2
hot water boiler correct answers only
1
(b) less electricity / energy to be generated / needed from power stations accept less demand
1
reduction in (fossil) fuels being burnt accept correctly named fuel accept answer in terms of: fewer light bulbs required because they last longer (1 mark) less energy used / fuels burnt in production / transport etc. (1 mark) ignore reference to CO
2 or global warming
ignore reference to conservation of energy 1
[5]
M2. light; sound; heat; kinetic/movement
for 1 mark each [4]
M3. (a) (i) 15*
(ii) 60*
[* if incorrect but (ii)>(i) and (i) + (ii) = 75 then credit 1 mark]
(iii) 25 each for 1 mark
3
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(b) stove because more of the energy heats up room / heats the room more or less energy escapes up chimney / less energy wasted
[Do not allow ‘less waste’ with the stove] or no un burnt fuel in smoke reason for 1 mark
1 [4]
M4. (a) (i) any one from:
water to the mug water to the air mug to the air mug to the table
both required direction of transfer must be correct
1
(ii) when temperatures are the same accept a specific example eg when the temperature of the water and mug are the same accept radiant heat transfer will never stop
1
(b) wood 1
(c) (i) conduction
accept convection if not given as 3 answer
1
insulator 1
convection 1
(ii) any one from:
do not accept any rebuilding of house
double glazing
loft insulation accept roof for loft
1
rd
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carpets
(cavity) wall insulation do not accept closing doors and windows
draft excluders
foil behind radiators accept blocking chimney
paint inside walls white [7]
M5. (a) 60% sector correct other two sectors closer to 13:7 than 12:8 or 14:6 sectors correctly labelled (w.r.t rank order of size)
each for 1 mark 3
(b) (i) ideas that wasted energy is transferred to surrounding air pan stove is converted to another/correctly named energy form
any 2 for 1 mark each 2
(ii) 40 for 1 mark
1 [6]
M6. (a) (heat) is conducted through the glass
the answers must be within the context of the question 1
(heat) passes through glass and air by radiation both glass and air required
1
(heat) crosses the air gap by convection mention of conduction through air is neutral
1
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(b) any one from
light accept sunlight
gamma rays
X-rays
radio accept sound or ir or microwaves or electromagnet waves
1
(c) any two from
cuts down convection currents accept stops air moving
air pockets trap air (from moving) accept has air pockets do not accept stops heat moving or traps heat
foam is a poor conductor air in the foam is a good insulator accept air is a good insulator in air pockets for both marks
2
(d) evaporation (of the water) do not accept rain is cold
1
takes energy from the house accept takes heat away or higher energy molecules leave first
1 [8]
M7. (a) (i) the outlet mark
hot water rises or floats up
do not accept heat rises
the inlet mark 1
cold water replacing any drawn off comes in at the bottom and does not mix with hot or cool the hot water
do not accept descriptions of a convection current 1
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(ii) only heats top (of tank) or a small volume
credit heats less water 1
no mixing occurs with cold because hot water is less dense or water is a poor conductor
no mixing because cold water is more dense 1
(b) radiation (losses from tank) do not accept reflection of heat
1
lower from light or white or shiny surfaces
credit they are poor radiators for both marks 1
[6]
M8. (a) (i) Carries heat up (as convection current) 1
(ii) (1) By conduction or from molecule to molecule (2) By radiation or as IR
2
(iii) Use shiny surface (inside or outside) or small area 1
(b) (i) Rise more quickly 1
(ii) Dull surface good absorber (accept “attract” = “absorb” if context correct, then penalise spg mark.
Shiny surface poor absorber 2
(c) (i) Fall more quickly 1
(ii) Dull surface good emitter Shiny surface poor emitter
2 [10]
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M9. (a) insulation
allow example e.g fibreglass 1
double glazing allow curtains
1
draught excluder allow double glazing / close fitting door allow turning down thermostat once only / turn down the heating
1
(b) transfers more useful energy allow converts more energy into light / less into heat / less energy wasted
1 [4]
M10. (i) D, C or B, in either order, then A
tick or cross on the A 1
(ii) matt absorbs energy (better than shiny) the converse arguments are acceptable
1
black absorbs energy (better than white) 1
[3]
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E1. In part (a) those candidates who chose the payback route generally gained no credit, unless they picked the boiler as the best option. Many candidates scored two marks for selecting the boiler and a correct calculation. A significant number of candidates scored all three marks for completing all the calculations correctly and making the correct choice.
Few candidates scored 2 marks in part (b). Most candidates failed to link the less energy back to the power station. The common mark scored was for stating the reduction in fuel burnt. Many considered the efficiency of the bulbs; but did not link it back to the need to generate less electricity. Very few thought about the need for fewer bulbs and the energy saving in their manufacture. There were a significant minority of candidates who thought that conventional light bulbs emit carbon dioxide or that energy loss somehow produces carbon dioxide, often as a result of heat loss.
E2. An easy start to the paper. Almost all candidates gained at least some marks, most gaining 3/4 marks.
E4. In part (a), the majority of candidates were able to identify from the word box the suitable sources and destinations for the heat energy but only a minority appreciated that heat transfer continues until temperatures become equal. In part (b) wood was generally correctly identified as the renewable type of fuel. The theory and practice of reducing heat energy loss from a house was widely understood. However a significant number of candidates apparently thought that electric currents pull cold air into a room.
E5. Part (a) was handled well by most candidates, though neatness and accuracy could have been better. Few candidates were able to explain to where the wasted energy had been transferred except ‘into the air’, and hence the answer given to (b)(ii) was usually 20% rather than 40%.
E6. Foundation Tier
Again this was a poorly answered question. In part (a), even those candidates who understood the mechanisms of conduction, convection and radiation failed to apply their knowledge to the situation described in the question.
Most candidates were able to pick up a mark in part (b) for mentioning light or sound. In part (c) very few mentioned trapped air in the cavity wall insulation.
The cooling effect of evaporation in part (d) appears to be little known. Again, those candidates who mentioned evaporation often failed to relate this knowledge to the particular context of the question.
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Higher Tier
Although candidates showed good knowledge of the mechanisms of the three transfer processes in part (a), it was poorly answered in the context of the question. Candidates had considerable trouble expressing themselves coherently. Few attained the radiation mark. There may have been some confusion, since pupils are taught that double glazing reduces heat loss but science must be capable of being applied as well as regurgitated. Some candidates thought the diagram showed a window with an air gap open at the top. Many candidates described convection within the room or radiation from a radiator or from the Sun. Some had warm air ‘going’ through the glass.
A pleasing number of candidates answered part (d) well, though many failed to link energy ‘needed’ with evaporation.
E7. In (a) most candidates failed to attain both marks. Few mentioned hot and cold water would not mix. Candidates tended not to relate their answers to the context. Many stated ‘heat rises’, with no integration of science to the situation.
In (b) only the most able candidates could explain that pale shiny surfaces minimise energy loss by reducing loss of radiant energy, as they are poor radiators. Weaker candidates focused on the reflective nature of light surfaces.
E9. (a) This part was generally well done but weaker candidates gave ‘insulation’ or ‘double glazing’ indiscriminately.
(b) This was less well answered, with most being in terms of ‘using less energy’ or ‘lasting longer’.
E10. Part (a) was generally well answered. Many candidates that failed to achieve on this question were writing about ‘light’ rather than thermal energy being absorbed or reflected. A worrying number said that black ‘attracts’ heat.
