IGCSE Physics 0625 — Topic 2: Thermal Physics — Paper 2 (MCQ) Cambridge Challenge

Question 1

A scientist uses a powerful microscope to observe tiny fat droplets suspended in milk. The droplets are seen to move in random, zigzag paths.

Which statement correctly explains why the fat droplets move in this way?

AThe fat droplets repel each other electrically BConvection currents in the milk push the droplets along predictable paths CWater molecules in the milk collide with the fat droplets randomly and unevenly from all sides DThe microscope light heats the droplets, causing them to vibrate

Question 2

The diagram shows four containers holding the same substance at different temperatures. The dots represent particles.

If the substance has a melting point of 40 °C and a boiling point of 120 °C, which diagram best represents the substance at 90 °C?

ADiagram A BDiagram B CDiagram C DDiagram D

Question 3

A sealed rigid steel cylinder contains nitrogen gas. The cylinder is moved from a cold storeroom at 7 °C into a factory at 27 °C.

What is the ratio of the final gas pressure to the initial gas pressure?

A27 / 7 B300 / 280 C280 / 300 D20 / 7

Question 4

A student sets up a Brownian motion experiment and heats the air in the glass cell. What happens to the motion of the visible smoke particles?

AThe motion becomes slower and more regular BThe motion stays the same because smoke particles are not affected by temperature CThe particles stop moving as they absorb the heat energy DThe motion becomes faster and more vigorous because air molecules move faster and hit the smoke particles harder

Question 5

An industrial gas storage tank holds compressed gas at 300 kPa and 27 °C. At night, the temperature drops to −23 °C. The tank is rigid so its volume does not change.

What is the new gas pressure?

A230 kPa B350 kPa C277 kPa D250 kPa

Question 6

Which row correctly describes the differences between evaporation and boiling?

AEvaporation: occurs at any temperature, only at the surface | Boiling: occurs at a fixed temperature, throughout the liquid BEvaporation: occurs at the boiling point, throughout the liquid | Boiling: occurs at any temperature, only at the surface CEvaporation: occurs at any temperature, throughout the liquid | Boiling: occurs at a fixed temperature, only at the surface DEvaporation: occurs at a fixed temperature, only at the surface | Boiling: occurs at any temperature, throughout the liquid

Question 7

In a desert survival course, the instructor wraps a wet cloth around a water bottle and places it in a breeze.

Why does the water inside the bottle stay cooler than the surrounding air?

AThe fastest water molecules evaporate from the cloth, removing thermal energy from the bottle BThe cloth reflects infrared radiation from the Sun CThe cloth is a thermal insulator that prevents heat entering DThe breeze pushes hot air molecules away from the bottle

Question 8

A gas in a sealed container has a volume of 400 cm³ at a pressure of 150 kPa. The gas is compressed at constant temperature until the pressure is 300 kPa. What is the new volume?

A100 cm³ B200 cm³ C600 cm³ D800 cm³

Question 9

Which statement about the relationship between temperature and kinetic energy of gas particles is correct?

AAt a given temperature, all gas particles have exactly the same kinetic energy BThe temperature of a gas in °C is directly proportional to the average kinetic energy of its particles CThe temperature of a gas in kelvin is related to the average kinetic energy of its particles DDoubling the temperature in °C always doubles the average kinetic energy of the particles

Question 10

A student blows up a balloon and ties it. She places the balloon in a freezer at −20 °C for one hour.

Which statement correctly explains what happens to the balloon?

AThe balloon expands because gas particles condense inside BThe balloon shrinks because the gas particles become smaller in cold temperatures CThe balloon stays the same size because the number of particles has not changed DThe balloon shrinks because gas particles lose kinetic energy and exert less force on the walls

Question 11

A scuba diver’s air tank holds 12 litres of air at a pressure of 20 000 kPa at the surface. At a certain depth, the external pressure is 400 kPa.

If the diver releases air from the tank at this depth, what volume would the 12 litres of tank air occupy at the external pressure? (Assume constant temperature.)

A0.24 litres B240 litres C600 litres D960 litres

Question 12

Which of the following does not increase the rate of evaporation of a liquid?

AIncreasing the surface area of the liquid BBlowing air across the liquid surface CIncreasing the humidity of the air above the liquid DRaising the temperature of the liquid

Question 13

A car tyre contains air at a pressure of 250 kPa and temperature 17 °C. After a long drive on the M25 motorway, the tyre temperature rises to 57 °C. The volume of the tyre does not change significantly.

What is the new pressure in the tyre?

A284 kPa B330 kPa C750 kPa D838 kPa

Question 14

A gas occupies 800 cm³ at 100 kPa and 27 °C. The gas is heated to 327 °C at constant pressure. What is the new volume?

A400 cm³ B1600 cm³ C9693 cm³ D2400 cm³

Question 15

A bimetallic strip is made from brass bonded to iron. Brass expands more than iron when heated.

When the strip is heated strongly, which way does it bend?

AIt bends towards the brass side BIt bends towards the iron side CIt stays straight because the metals are bonded together DIt twists into a spiral

Question 16

A 500 g copper block (specific heat capacity = 390 J/(kg °C)) is heated from 25 °C to 75 °C.

How much energy is supplied to the block?

A9 750 J B14 625 J C975 000 J D19 500 J

Question 17

The graph below shows the temperature of a substance as it is heated at a steady rate from −20 °C.

During which section of the graph is latent heat of vaporisation being supplied?

AP BQ CR DS

Question 18

Referring to the same heating curve above, during section Q, what is happening to the substance?

AThe solid is increasing in temperature BThe substance is melting — solid is changing to liquid at a constant temperature CThe liquid is boiling and changing to gas DThe gas is cooling and condensing

Question 19

An immersion heater rated at 2000 W is used to heat 1.5 kg of water from 20 °C to 80 °C. The specific heat capacity of water is 4200 J/(kg °C).

Assuming no heat losses, how long does it take?

A63 s B126 s C189 s D252 s

Question 20

A chef heats 200 g of cooking oil (c = 2000 J/(kg °C)) and 200 g of water (c = 4200 J/(kg °C)) using identical heaters that supply equal energy.

After the same energy is supplied to each, which statement is correct?

AThe oil has a lower temperature rise because it has a lower specific heat capacity BBoth liquids have the same temperature rise because they have the same mass CThe oil has a higher temperature rise because it has a lower specific heat capacity DThe water reaches a higher temperature because water stores more energy

Question 21

0.5 kg of ice at 0 °C is completely melted to water at 0 °C. The specific latent heat of fusion of ice is 334 000 J/kg.

How much energy is needed?

A668 J B167 000 J C334 000 J D668 000 J

Question 22

A student heats 250 g of a liquid and records the following data:
Energy supplied = 15 750 J, Temperature rise = 30 °C.

What is the specific heat capacity of the liquid?

A210 J/(kg °C) B2100 J/(kg °C) C1890 J/(kg °C) D21 000 J/(kg °C)

Question 23

An ice cream maker cools 300 g of a cream mixture from 20 °C to −10 °C. The mixture has a specific heat capacity of 3000 J/(kg °C) as a liquid, a freezing point of 0 °C, a specific latent heat of fusion of 200 000 J/kg, and a specific heat capacity of 2000 J/(kg °C) as a solid.

What is the total energy that must be removed from the cream mixture?

A18 000 J B78 000 J C84 000 J D24 000 J

Question 24

The graph shows the cooling curve of a substance that starts as a gas at 300 °C.

What are the boiling point and melting point of this substance?

ABoiling point = 300 °C, Melting point = 200 °C BBoiling point = 200 °C, Melting point = 80 °C CBoiling point = 80 °C, Melting point = 200 °C DBoiling point = 300 °C, Melting point = 80 °C

Question 25

Railway tracks in the United Kingdom are laid with small gaps between sections.

Why are these expansion gaps necessary?

ATo allow rainwater to drain away from the track surface BTo reduce the noise produced by passing trains CTo allow the steel rails to expand in hot weather without buckling DTo make it easier to replace damaged sections of track

Question 26

During which process does a substance release latent heat?

AHeating a liquid from 20 °C to 50 °C BMelting ice at 0 °C CBoiling water at 100 °C DSteam condensing at 100 °C

Question 27

Referring to the heating curve in Q17, sections R and P both show rising temperature.

Why is the gradient (steepness) of section R different from section P?

AThe substance is being heated at a different rate in section R BThe substance has changed state, so it has a different specific heat capacity as a liquid compared to a solid CThe mass of the substance has changed during melting DThe thermometer becomes less accurate at higher temperatures

Question 28

A kettle supplies 504 000 J of energy to 2.0 kg of water already at 100 °C. The specific latent heat of vaporisation of water is 2 260 000 J/kg.

What mass of water is converted to steam?

A0.022 kg B0.22 kg C2.0 kg D4.49 kg

Question 29

A student touches a metal door handle and a wooden door in the same room. Both are at 20 °C (below body temperature).

The metal handle feels colder than the wooden door. Which explanation is correct?

AThe metal is at a lower temperature than the wood BMetal is a better conductor, so it transfers thermal energy away from the hand more quickly CWood absorbs more infrared radiation from the hand DMetal contains more thermal energy per kilogram than wood

Question 30

A thermos flask is designed to keep liquids hot for a long time. It has double walls with a vacuum between them, and the inner surfaces are silvered.

Which row correctly explains how each feature reduces heat loss?

AVacuum reduces conduction and convection | Silver surfaces reduce radiation BVacuum reduces radiation | Silver surfaces reduce conduction CVacuum reduces convection only | Silver surfaces reduce evaporation DVacuum reduces all three methods | Silver surfaces are decorative

Question 31

A spacecraft re-entering the Earth’s atmosphere generates extreme heat due to friction with air molecules. The heat shield on the spacecraft has a light-coloured, rough outer surface.

Why is the outer surface light-coloured rather than dark?

ALight surfaces are better emitters of infrared radiation, so heat is radiated away faster BLight surfaces are poorer absorbers of infrared radiation from the Sun during re-entry CLight surfaces are better conductors of heat DLight surfaces prevent convection from occurring

Question 32

Why does a metal saucepan have a plastic or wooden handle?

APlastic is a better emitter of infrared radiation than metal BPlastic is a poor thermal conductor, so less thermal energy reaches the cook’s hand CPlastic prevents convection currents forming in the handle DPlastic has a higher specific heat capacity than metal

Question 33

An industrial cooling tower uses large fans to blow air over thin pipes containing hot water from a factory.

Which methods of thermal energy transfer are used to cool the water in the pipes?

AConduction only BConvection only CConduction through the pipe walls and forced convection by the moving air DRadiation only, because the hot pipes emit infrared

Question 34

Two identical metal cans are filled with equal volumes of hot water. Can X is painted matt black and Can Y is painted shiny white. Both are placed in the same room.

After 30 minutes, which can has cooled more, and why?

ACan Y, because white surfaces reflect heat back inside the can BCan X, because matt black surfaces are better emitters of infrared radiation CBoth cool at the same rate because they contain the same volume of water DCan X, because black surfaces are better conductors of heat

Question 35

Coastal cities like Plymouth tend to have milder climates — cooler in summer and warmer in winter — compared to inland cities like Birmingham.

Which property of water is mainly responsible for this moderating effect?

AWater is transparent, so it reflects sunlight easily BWater is a poor conductor of heat CWater has a very high specific heat capacity, so it heats up and cools down slowly DWater evaporates easily, creating clouds that block sunlight

Question 36

Why are the heating coils in an electric kettle placed at the bottom rather than the top?

ATo transfer heat by radiation to the water above BSo that heated water rises and is replaced by cooler water, creating convection currents that heat all the water efficiently CTo make the kettle more stable DBecause heat only travels downward through liquids

Question 37

Energy from the Sun reaches the Earth through the vacuum of space. Which method of thermal energy transfer is responsible?

AConduction, because the Sun’s energy passes through the particles of space BConvection, because hot gases expand and rise from the Sun to the Earth CRadiation, because electromagnetic waves (including infrared) can travel through a vacuum without needing particles DA combination of conduction and convection through the solar wind

Question 38

A volcanic hot spring in Iceland has water at 70 °C. A swimmer notices that the water near the surface is hotter than the water near the bottom of the pool, even though the hot water enters at the bottom.

Why is the surface water hotter?

AInfrared radiation from the Sun heats the surface water BThe hot water is less dense than the cooler water and rises to the surface by convection CHeat is conducted upward through the water from bottom to top DThe cold water at the bottom absorbs all the thermal energy

Question 39

Four identical containers of hot water are placed in a room. Each container has different outer surface properties.

Which container will cool the fastest?

AShiny silver surface BShiny white surface CMatt white surface DMatt black surface

Question 40

A student investigates conduction by holding rods of four different materials (copper, aluminium, glass, and wood) of the same dimensions with wax-attached pins at one end. The other ends are placed in hot water simultaneously.

The pins drop off at different times. Which conclusion is best supported by this experiment?

AAll materials conduct heat at the same rate but metals are hotter BMetals are better thermal conductors than non-metals; copper conducts better than aluminium CThe wax melts at different temperatures on different materials DNon-metals conduct heat faster than metals because they have more free electrons

Paper 2 — Multiple Choice

Section A: Kinetic Particle Model (2.1)

Section B: Thermal Properties and Temperature (2.2)

Section C: Transfer of Thermal Energy (2.3)