iGCSE 4B Part 2 Conduction Convection

RadiationPractice Exam Questions

Qu. Mark MaxImprovement

pointSKREAM

1 5

2 6

3 8

4 5

5 10

6 4

7 12

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Overall Comment

Page 1 of 16

S I made a silly slip

K I just did not know the science

R I misread the question

E My writing was not clear/ detailed

A I did not apply the knowledge

M I applied the maths incorrectly

Questions…

Q1.The diagram shows how the metal chimney from a log-burning stove passes through the inside of a house.

 

(a)     Explain how heat is transferred by the process of convection from the inside of the stove to the top of the chimney.

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(b)     Although the outside of the chimney becomes very hot, there is no insulating material around the chimney.

(i)      Explain, in terms of the particles in a metal, how heat is transferred by conduction from the inside to the outside of the metal chimney.

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(ii)     Suggest one advantage of having no insulation around the chimney.

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(Total 5 marks)

Q2.The diagram shows a metal pan being used to heat water.

 

Energy from the gas flame is transferred through the metal pan by conduction.

Explain the process of conduction through metals.

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(Total 4 marks)

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Q3.(a)     The figure below shows a fridge with a freezer compartment.

The temperature of the air inside the freezer compartment is –5 °C.

 

The air inside the fridge forms a convection current when the fridge door is closed.

Explain why.

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(b)     The table below shows information about four fridges. 

Fridge Volume in litres Energy used in one year in kWh

A 250 300

B 375 480

C 500 630

D 750 750

A householder concludes that the energy used in one year is directly proportional to the volume of the fridge.

Explain why her conclusion is not correct.

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Use data from the table in your answer.

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(c)     New fridges are more efficient than fridges made twenty years ago.

Give one advantage and one disadvantage of replacing an old fridge with a new fridge.

Ignore the cost of buying a new fridge.

Advantage __________________________________________________________

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Disadvantage _______________________________________________________

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(Total 8 marks)

Q4.The diagram below shows an electric kettle and the label on the bottom of the kettle.

 

The water at the bottom of the kettle will heat up first.This is because the heating element is near the bottom of the kettle.Convection currents will then cause the rest of the water in the kettle to be heated.

(i)      What are convection currents?

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(ii)      Explain how convection currents are produced.(Your answer should refer to density and temperature.)

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(Total 5 marks)

Q5.(a)     The diagram shows an immersion heater used to heat water inside a tank. Heat is

transferred through the water by convection.

 

(i)      Draw arrows on the diagram to show the movement of the water in the tank when the heating element is switched on.

(2)

(ii)     Explain how a convection current is set up in the water. The explanation has been started for you.

When the heating element is switched on, the hot water nearest the element rises

because ______________________________________________________

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(b)     The diagram shows two ways to reduce heat loss through the walls of a house.

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(i)      How is the aluminium foil able to reduce heat loss?

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(ii)     The plastic foam is good at reducing heat loss through the walls. Explain why.

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(c)     Evaporation is an important heat transfer process. When sweat evaporates, it takes heat energy from your body. As humidity increases, you are more likely to feel hot and uncomfortable. Explain why.

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(Total 10 marks)

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Q6.(a)     Infra red radiation can be reflected, absorbed and transmitted by glass.

 

(i)      What percentage of infra red is absorbed by the glass?

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(ii)     Complete the following sentence by drawing a ring around the correct word or phrase.

 

The absorbed infra red

increases

does not change

decreases

the temperature of the glass.

(1)

(b)     Two of the following statements are true. One of the statements is false.

Tick ( ) the boxes next to the two true statements. 

All objects absorb infra red radiation.  

Black surfaces are poor emitters of infra red radiation.  

A hot object emits more infra red than a cooler object.  

(1)

(c)     The following statement is false. 

Black surfaces are good reflectors of infra red radiation.

Change one word in this statement to make it true.

Write down your new statement.

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(Total 4 marks)

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Q7.All objects emit and absorb infrared radiation.

(a)     Use the correct answer from the box to complete each sentence. 

dark matt dark shiny light matt light shiny

The best emitters of infrared radiation have

_____________________________________ surfaces.

The worst emitters of infrared radiation have

_____________________________________ surfaces.(2)

(b)     Diagram 1 shows a sphere which is at a much higher temperature than its surroundings.

Diagram 1

 

 

Energy is transferred from the sphere to the surroundings.

The table shows readings for the sphere in three different conditions, A, B and C. 

Condition Temperature ofsphere in °C

Temperature ofsurroundings in °C

      A 70 5

      B 80 0

      C 90 30

In each of the conditions, A, B and C, the sphere transfers energy to the surroundings at a different rate.

Put conditions A, B and C in the correct order.

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Give a reason for your answer.

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(c)     Diagram 2 shows a can containing water.

A student investigates how quickly a can of water heats up when it is cooler than room temperature.

Diagram 2

 

The student has four cans, each made of the same material, with the following outer surfaces.

 

dark matt dark shiny light matt light shiny

The student times how long it takes the water in each can to reach room temperature.

Each can contains the same mass of water at the same starting temperature.

(i)      Which can of water will reach room temperature the quickest?

Give a reason for your answer.

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(2)

(ii)     Apart from material of the can, mass of water and starting temperature, suggest three control variables for the student’s investigation.

1. ____________________________________________________________

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2. ____________________________________________________________

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3. ____________________________________________________________

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(d)     The photographs show two different foxes.

     Fox A                                                Fox B

              By Algkalv (Own work) [CC-BY-3.0],                                                          © EcoPic/iStock

                    via Wikimedia Commons

 

Which fox is better adapted to survive cold conditions?

Give reasons for your answer.

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(Total 12 marks)

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iGCSE (Pre – 2017 Questions)

Mark schemes

Q1.(a)     any two from:

•        (air) particles / molecules / atoms gain energy

•        (air) particles / molecules / atoms move fasterdo not accept move moredo not accept move with a bigger amplitude / vibrate more

•        (air) particles / molecules / atoms move apart

•        air expandsignore particles expand

•        air becomes less denseignore particles become less dense

•        warm / hot air / gases / particles risedo not accept heat risesanswers in terms of heat particles negates any of the mark points that includes particles

2

(b)     (i)      any two from

•    free / mobile electrons gain (kinetic) energyaccept free / mobile electrons move fasteraccept vibrate faster for gain energy

•    free electrons collide with other (free) electrons / ions / atoms / particles

•    atoms / ions / particles collide with other atoms / ions / particlesanswers in terms of heat particles negates this mark point

2

(ii)     (faster) energy / heat transfer to room(s) / houseaccept room(s) / house gets warm(er)accept lounge / bedroom / loft for rooms

1[5]

Q2.accept atoms / particles for ions throughout

(a metal has) free electronsaccept mobile for free

1

(kinetic) energy of (free) electrons increasesaccept energy of ions increases

12

iGCSE (Pre – 2017 Questions)accept ions vibrate with a bigger amplitudeaccept ions vibrate moredo not accept electrons vibrate more

1

(free) electrons move faster1

or

electrons move through metalaccept electrons collide with other electrons / ions

(so) electrons transfer energy to other electrons / ionsaccept ions transfer energy to neighbouring ions

1[4]

Q3.(a)     air near freezer compartment is cooled or loses energy

accept air at the top is cold1

cool air is (more) dense or particles close(r) together (than warmer air)do not allow the particles get smaller / condense

1

so (cooler) air falls1

air (at bottom) is displaced / moves upwards / risesdo not allow heat risesaccept warm air (at the bottom) rises

1

(b)     if volume is doubled, energy use is not doubledorvolume ÷ energy not a constant ratio

1

correct reference to data, eg 500 is 2×250 but 630 not 2×3001

(c)     accept suitable examples, eg

advantage:

•        reduces emissions into atmosphere•        lower input power or uses less energy or wastes less energy•        costs less to run

cost of buying or installing new fridge is insufficientignore reference to size of fridge

1

disadvantage:

13

iGCSE (Pre – 2017 Questions)•        land fill•        energy waste in production•        cost or difficulty of disposal•        transport costs

1[8]

Q4.(i)      currents of moving liquids/gases/fluids carrying/transferring energy

(can name fluid)1

(ii)      liquids/gases expand when their temperature rises/when they are heated

          the density of the heated liquid/gas is then less than that of the colder liquid/gas which has not been heated

          the warmer/less dense liquid/gas then rises through the colder/denser liquid/gas

          the colder/denser liquid/gas falls to replace the liquid/gas which has risen,and in turn becomes heated

for 1 mark each4

[5]

Q5.(a)     (i)      convection current correctly shown

with arrows extending to aboveinsulation label line

circulation must show water rising in the left half of the tank accept continuous or broken arrows must be at least one arrow up and one arrow downallow 1 mark for correct diagram which does not extend high enough

2

(ii)     it expands or it gets less densedo not allow hot water risesdo not accept explanation in terms of molecules expanding or changing densitydo not accept lighter or heavier

1

more dense water fallsallow cold water falls if qualified with a suitable reason

1

          (b)     (i)      reflects heat back into the room or where it came fromaccept infrared or radiation or energy for heataccept bounce for reflect if in correct context

1

(ii)     air is a (good) insulator or poor conductor or air stops conduction

14

iGCSE (Pre – 2017 Questions)do not accept plastic foam is a good insulator  or bad conductor

1

air is trapped1

convection loss reduced or stopped1

(c)     two out of the following three:any answer which gains credit must contain a comparison

rate of evaporation decreasesaccept less sweat can evaporate or evaporation is more difficult

          less heat energy removed from the body

          higher humidity the less water vapour can be absorbed (into the air)accept sweat for water vapourdo not credit description of high humidityaccept a correct answer in terms of dynamic equilibrium

2[10]

Q6.(a)     (i)      25 (%)

do not accept ¼1

(ii)     increases1

(b)     tick ( ) in top and bottom boxboth required

1

(c)     SHINY surfaces are good reflectors of infra-red radiationaccept white for shiny

          or black surfaces are POOR reflectors of infra-red radiationaccept bad for pooraccept insertion of ‘not’ before ‘good’ in statement

          or black surfaces are good EMITTERS of infra-red radiation

          or black surfaces are good ABSORBERS of infra red radiation1

[4]

Q7.(a)     dark matt

1

15

iGCSE (Pre – 2017 Questions)light shiny

1

(b)     B      A      C1

biggest temperature difference (80 °C)dependent on first mark

1

(c)     (i)       (the can that is) dark matt1

best absorber (of infrared radiation)1

(ii)     any three from:

•        same area / shape of can•        surrounding temperature is the same for all cans•        same surface underneath cans•        same position in the room

3

(d)     fox A

smaller ears1

thicker fur1

these minimise energy transferdependent on first 2 marks

1[12]

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