This page contains the AQA GCSE Physics P2 Energy Transfer by heating Kerboodle Answers for revision and understanding of AQA GCSE Physics P2 Energy Transfer by Heating. This page also contains the link to the notes and video for the revision of this topic.
1 a Steels pans have handles made of plastic or wood as they are insulators which means they are poor conductors of heat do not allow heat to pass through them so they will be safe to be used as handles.
b Felt is better insulator than paper because it traps air and it is the air that is the air that act as a thermal insulator.
2 a Sealskin, wool, fur can be used to line a pair of boots as they stop air passing through it and traps the air. The air then acts as an insulator so we can use them to line a pair of winter boots.
b To test three different materials we will take hot water and measure its starting temperature. We will then wrap the hot water with one lining and records its temperature after fixed intervals like every 5 minutes and take 10 readings.
We will then again heat water at the same starting temperature and wrap it with the second materials and again take temperature reading for fixed interval of 5 minutes and take 10 readings.
We repeat this for the third material. We will record the data. The materials where the biggest drop in the temperature is observed will be a poor insulator.
3 The thickness of the insulating materials affects the energy transfer through it. Greater the thickness less will be the rate of energy transfer and better insulation it will provide. We can take a hot water and measure its starting temperature and then wrap it with single layer of insulation and record the temperature change of water every 10 minutes and take around 5-6 readings. We can again repeat this procedure with double layer of insulation and then triple layer and so on. We can plot the graph of the temperature change with time for all the different layers. We will observe greater the number of layers less will be drop in temperature so better insulation it will provide.
4 B Glass rod, will keep the wax in the solid state for longer time as compared to copper rod and steel rod as glass rod has a least thermal conductivity. The energy transfer by conduction through a material depends on its thermal conductivity.
1 Infrared radiations are the part of the electromagnetic spectrum which lies in between Visible rays and microwaves. They have wavelengths greater than visible light but smaller than microwaves.
2 a More infrared radiation is emitted from the city at night as compared to rural areas as cities have big buildings and structures. All objects emit infrared radiations so cities email greater heat.
b IF we put our hand near electronic iron it will radiate heat and we can feel the heat without even touching it.
3 a Hot objects emit more of their light at shortest wavelengths so color of the nail became dull-red then orange-red.
b i Hot objects emit more of their light at shortest wavelengths so Z star is hotter because of their shortest wavelength which is of white colour.
II Coolest objects emit more of their light at longest wavelength so Y star is coolest as it is of red colour.
1 The similarity between the radiation emitted and absorbed from the sun is that the amount of energy absorbed and emitted are the same. The difference between the radiation emitted and absorbed from the sun is that the wavelength of radiation emitted is longer than the wavelength of the radiation absorbed.
b If night is very clear, heat emitted from the earth’s surface freely escapes into space, resulting in colder temperatures.
2 a The interior of a closed car in the sunlight will be higher because of a greenhouse effect. The glass of the car is transparent to visible light, so that energy is absorbed by the interior of the car (the seats, dashboard, and floor) increasing their temperature. The car absorbs the energy of shorter wavelength but emits the energy of longer wavelength. Those items then emit infrared radiation and the glass is fairly opaque to the longer wavelength radiation and the energy stays in the car. So more energy comes in the glass than is escaping out of the glass making the temperature in the car much higher than the outside.
b In the shaded area, the amount of light will be less so less light will be absorbed making the car less hotter.
3 If there were no Greenhouse gases in the atmosphere then all the radiation absorbed by the Earth will be reflected back making the Earth’s temperature too low for living. The Greenhouse gases make a blanket around the Earth’s atmosphere prevents the radiation from escaping into the space and reflect them back to the Earth. This makes the temperature of the Earth warmer.
1 A small bucket of water when left in strong sunlight will warm faster, first because there is a smaller volume of water to be heated, and secondly because the ratio of surface area to volume is greater in the small bucket. In other words, there are more square centimeters of surface area per cubic centimeter of water. Since the energy from the sun must be absorbed through the surface area (both of the water and of the outside of the bucket), a greater surface:volume ratio favors faster heating.
2 Lead has a lower specific heat capacity than aluminium because of greater molecular mass. Since lead has a lower specific heat capacity it warms up more quickly than aluminium.
b i Q=mcΔT
so to raise the temperature of 0.20 kg of aluminium from 15 degrees to 40 degrees 4500 J of energy is required.
Mass (m) = 0.20 Kg
Specific heat capacity of Aluminium (c) = 900 J/KgC
Temperature Change (ΔT) = 40-15 = 25 C
0.20*900*25 = 4500J
ii Q=mcΔT = 0.40*4200*25=42000J
so to raise the temperature of 0.40 Kg of water from 15 degrees to 40 degrees 42000 J of energy is required.
Mass (m) = 0.40 Kg
Specific heat capacity of water = 4200 J
Temperature change (ΔT) = 40-15 = 25 degrees
Q=mcΔT = 0.40*4200*25=42000J
III so to raise the temperature of 0.40 Kg of water from 15 degrees to 40 degrees in an aluminium containers 42000 J of energy is required as the container will not affect the specific heat capacity of water.
Q=mcΔT=0.40*4200*25=42000J
Q= 150*4200*40
=25200 KJ
Energy required to heat the tank
= 20 (mass of tank) * 385 (specific heat capacity of copper) * 40 (temperature change)
= 308 KJ
So the total energy required to heat the water and the tank together = 25508 KJ
3 Storage heater uses bricks to store energy and they provide heat for a longer time. On the other hand they take more time to get heated as compared to radiant heater as radiant heater which when plugged in converts electrical energy into infrared heat energy and warms the surroundings.
c= E/mΔT
1 a Cavity wall insulation is better than the air in the cavity because cavity wall insulation traps air into small packets. Air is a great insulator for small spaces. As a space gets larger, the temperature on one side will heat the air on that side, causing it to rise, displacing cooler air and causing that cooler air to heat up. This forms a feedback loop called a convection current. The larger the air cavity, the more easily the air can move. Cavity insulation traps very small air pockets next to each other. The better the insulation, the better it traps these air pockets. By Cavity insulation the insulations is improved and convection currents are also prevented.
b Aluminium foil is placed behind the radiator wall to reflect the heat away from the wall. The intention is to reduce heat losses into the wall by reflecting radiant heat away from the wall.
2 a Plastic frame is better than a metal frame in windows as plastic is an insulator and is a poor conductor of heat so it prevents the heat from escaping.
3 We choose double glazed window with less gap width between the panes as the higher gap window panes will trap more air causing the energy loss due to convection.
4 It will cost £180 to buy and install the insulation.
Cost of 6 rolls = 15*6 = 90
Cost of installations = 90
Total = 90+90 = £180
b As each roll is saying £10 so six rolls will save £60.
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1 a i White hat is better to wear outdoors in summers than a black hat as white hat reflects more heat and absorb less so it will not feel hot to wear a white hat.
ii Smooth shiny surface are better for roof as compared to dark or matt surface as smmoth shiny surfaces reflects sunlight and therefore does not get as hot in sunlight, also radiates less energy to surroundings at night.
b Panel with transparent cover and matt black surface are better than the matt cover with a shiny base as the transparent cover will allow the radiation to pass through and the matt black surface will heat more quickly making it an effective heater. On the other hand black surface will absorb more light but a suitable conductor will be required to transmit the heat to the base which inturn can cause energy loss as well due to conduction.
2 a I By Conduction through plate the energy is transferred from the component to the plate.
II By Radiation (and convection) through air the energy is transferred from the plate to the surroundings.
b The metal Fins on the plates increase surface area of heat sink. Greater the surface area more is the heat loss from the plates.
c Copper will be a better option for a heat sink in a computer as it has a greater density and greater specific heat capacity than aluminium. Greater density means that sink will have a greater mass and higher heat capacity means that it will not heat up too quickly.
3 a Wool is a good insulator as fibres trap dry air in between the fibres which act as an insulator. The radiation from the body makes the wool warm but the trapped air does not allow the heat to escape, keeping the body warm.
b Hair act as an insulator as it traps air in between the hair follicles which keeps the head warm as it prevents the energy loss due to conduction. But exposed surface of the hair loses heat. The hat provides extra insulation by preventing heat loss from the exposed surface keeping the head warm.
c Ear has a greater surface area so it loses greater amount of heat from the body making the body cold. Therefore it is important to cover the ear to prevent heat from the ear from escaping.
4 a Infrared radiation from the body is reduced by the reflective coating inside the emergency blanket.
b Reflective coating acts as an insulator by trapping infrared radiation in space between body and Blanket. So the air in the spaces become warm and being an insulator it prevents the heat loss from the body preventing the runners from becoming cold.
5 Energy loss by the meterorite
For each kg: ΔE = 1% of 60 MJ = 600 000 J
ΔE = mcΔθ gives 600 000 J = 1.0 kg × 400 J/kg °C × Δθ
Δθ = 600 000 J /1.0 kg × 400 J/kg/oC
15 000 °C
b Yes the assumption is correct as the Surface material vaporised at temperature and small objects burn up before reaching the ground. Meteorites don’t burn completely so only part of their mass vaporised
6 In 1 s, mass of water water = 1.5 kg /60 s = 0.025 kg
ΔE = 0.025 kg × 4200 J/kg °C × (40 – 15) °C = 2625 J
b Useful energy transferred in 1 s = 2625 J, energy supplied in 1 s = E= Pt = 5000 W × 1 s = 5000 J
Efficiency = = 2625 J/ 5000 J × 100% = 53%
7 To compare the effect of huddling together we will take a beaker with the same amount of water. We will make groups of 1,2,3,4 and 5 cans together. All cans will have the same amount of hot water. We will record the temperature of the central can of each group at the fixed intervals of every 3 to 4 minutes for around 30 minutes. The temperature is recorded with time and graph is plotted for change in temperature with time. The graph will then be analysed and it will be observed that the bigger the group of lesser will be the change in temperature.
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01.1 Infrared heater is used in the investigation to mimic the sunlight
01.2 The two control variables in the investigation will be the Distance of the cards from the heater and the Size of card
01.3 The probe attached to data logger is much more sensitive and reduces the chances of human error in recording the temperature.
01.4 No it is not practical to cover the glaciers with the insulators as glaciers are too big
02.1 Copper will be better choice to be used in saucepan to heat food as it has the highest thermal conductivity.
02.2 We can put the hand near the saucepan and if it is hot it will radiate the heat or we can also use an infrared detector to detect the radiation emitted.
03.1 Q= 163800 J
Mass of water = 0.65 Kg
Specific heat capacity of water = 4200 J/Kg/C
Q= mct
So change in temperature = Q/mc
= 163800/4200*0.65
=60 degrees
Temperature change = 60 degrees
As the starting is 90 and temperature change is 60 degrees so the final temperature will be 90-60= 30 degrees
30°C
03.2 The bottle warmers cannot give the desired temperature but in the gel warmers we can control the temperature. The gel warmers cannot get too hot as well and scalding can also be avoided in gel warmers.
04.1 for 1 layer: A = 16.5°C (82.5-66) and B= 11.5°C (83-71.5)
for 2 layers: A = 9.5°C (81.5-72) and B = 7.5°C (75-67.5)
04.2 B is the better insulator because the temperature change for material B is less in both tests.
04.3 Use same starting temperature repeat the tests and can investigate with different layers.
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Disclaimer: I have tried by level best to provide the answers and video explanations to the best of my knowledge. All the answers and notes are written by me and if there is any similarity in the content then it is purely coincidental. But this is not an alternative to the textbook. You should cover the specification or the textbook thoroughly. This is the quick revision to help you cover the gist of everything. In case you spot any errors then do let us know and we will rectify it.
References:
BBC Bitesize
AQA GCSE Science Kerboodle textbook
Wikipedia
Wikimedia Commons
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This page contains the detailed and easy notes for AQA GCSE Physics Energy for revision and understanding Energy.
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DIFFERENT FORMS OF ENERGY
| ENERGY | DEFINATIONS | EXAMPLE |
| Thermal Energy | Energy from the heated objects. | Energy in Kettle |
| Light Energy | Energy that helps to see. | Bulb, Torch |
| Electrical Energy | Energy due to the flow of charge or current | Electrical Appliances |
| Chemical Energy | Energy stored in the chemical bonds | Food, Batteries |
| Sound Energy | Energy due to vibrations | Loudspeaker |
| Nuclear Energy | Energy stored in the nucleus of the atom | Nuclear Reactor |
| Kinetic Energy | Energy due to movement | Roller coaster moving down |
| Potential Energy | Energy due do the position | Ball raised to a height |
| Elastic Energy | Energy stored in stretch objects | Springs, Rubber |
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Law of Conservation of Energy: Energy is neither created nor destroyed. It changes from one form to another.
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Potential Energy P.E = m x g x h
Potential energy in Joules (J) g is the gravitational field strength in N/kg, and h is the height in metres (m).
Kinetic Energy K.E = ½ mv2
m is the mass in kilograms(kg), v is the speed(m/s) and the kinetic energy in joules(J).
Elastic Potential Energy E.P.E. = ½ ke2
Elastic potential energy in joules (J), k is the spring constant in N/m and e is extension in metres (m).
Efficiency = useful output/ Total input x 100
Efficiency is the relationship between the useful work done by a machine, an engine, a device, etc. And the energy supplied to it, often expressed as a percentage.
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Q1 Calculate the work done when 2 N of force moves a block to a distance of 2 m
W =F x S = 2 x 2 = 4J
Q2 Calculate the kinetic energy when a 2kg block moves at the speed of 3 m/s
K.E = ½ mv2
½ x 2 x 32 = 9J
Q3 Calculate the potential energy when the mass of 2 Kg is raised to a height of 5m above the ground.
P.E = mgh
2 x 10 x 5 = 100J (g = 10m/s2)
Q4 Calculate the energy dissipated by a 10 W bulb in 2 minutes
E = P x t
= 10 x 2 x 60
= 1200J
The extension produced in an elastic object is directly proportional to the force applied on it.
F ∝ e
F = ke
Elastic Potential Energy = ½ ke2
Energy efficiency, means using less energy to provide the same level of energy.
All appliances do not convert 100% of the input energy into useful energy.
The waste energy is dissipated to the surroundings.
Energy efficiency = Useful/total x 100
= 90/100 x 100
= 90%
| Device | Useful Energy | Waste Energy |
| Light Energy | Heat Energy | |
| Kinetic Energy | Heat and Sound Energy | |
| Heat Energy | Light and Sound |
Friction is the force that opposes the motion of the body.
It results in loss of energy.
Methods to prevent friction:-
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CONDUCTION
CONVECTION
RADIATION
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LOFT INSULATION
CAVITY WALL INSULATION
DOUBLE GLAZING
THICK BRICKS
FOILING
RENEWABLE
NON RENEWABLE
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Reliability
Cost
Demand – With the increase in global energy demand, common fossil fuels that produce energy, such as coal, oil and natural gas, are running out
Supply
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Disclaimer:
I have tried my level best to cover the maximum of your specification. But this is not the alternative to the textbook. You should cover the specification or the textbook thoroughly. This is the quick revision to help you cover the gist of everything. In case you spot any errors then do let us know and we will rectify it.
References:
BBC Bitesize
Wikipedia
Wikimedia Commons
Image Source:
Wikipedia
Wikimedia
Commons
Flickr
Pixabay
Make sure you have watched the above videos and are familiar with the key definations before trying these questions. It is also good to time yourself while doing these questions so that you can work on the speed as well.