Thermal physics

Which method of thermal energy transfer can take place through a vacuum?

Air directly above a hot heater rises. Why does this happen?

Four metal plates are all at the same temperature. They have different surface finishes. Which plate emits infrared radiation at the greatest rate?

Rods of copper, glass, wood and steel have the same length and thickness. A small bead of wax is stuck to one end of each rod. The other ends are placed in boiling water at the same time. The wax on the copper rod melts first. What does this show?

Which statement describes the particles in a liquid?

The air in a classroom is at a temperature of 27 °C.
What is this temperature in kelvin?

A sealed metal can of air is heated. The volume of the can does not change.
Why does the pressure of the air in the can increase?

A bicycle pump is sealed at the end. The piston is pushed in slowly, so the temperature of the air inside stays the same.
Why does the air pressure increase?

A concrete road is laid in sections. Small gaps are left between the sections and filled with a soft, flexible material.
Why are the gaps left?

Pure water is boiling in an open pan at standard atmospheric pressure. The pan continues to be heated.
What happens to the temperature of the water while it is boiling?

Hot liquid wax is left to cool. Its temperature is measured every minute. For several minutes, the temperature stays constant at 52 °C, even though the wax is still losing energy to the surroundings.
What is happening to the wax during this time?

Overhead electricity cables are hung between tall pylons. Engineers fit the cables on a warm summer day.

A student has two identical metal cans. One is painted dull black and the other is polished shiny silver. She fills each can with hot water at 80 °C and records the temperature of the water every minute as it cools in a room at 20 °C.

A block of copper, some liquid cooking oil and the air above them are all at room temperature.

What happens to the particles of a substance at absolute zero (−273 °C)?

This question is about the changes of state of water.

A sealed rigid steel canister contains air. The canister is left in the sun and the air inside warms up. Which statement explains the increase in gas pressure?

Why is a metal spoon in hot soup much hotter at its handle after a minute than a plastic spoon of the same size?

A steel bridge is slightly longer on a hot afternoon than on a cold morning. Which statement explains this thermal expansion?

The particle model is used to explain the properties of solids, liquids and gases.

A saucepan of water is heated on an electric hob. The base of the saucepan is made of metal. The handle is made of plastic.

The air in a sealed brake reservoir on a train is warmed by strong sunshine. The volume of the reservoir does not change. Which statement explains why the air pressure rises?

On a frosty morning a metal handrail on a station platform feels much colder to touch than a wooden bench, although both are at the same temperature. What is the reason?

Liquid water has been detected beneath the surface of a distant moon. Which row describes the particles in a liquid?

Steel railway lines are laid in long sections with small gaps between the ends on a hot day.

A marathon runner is given a thin shiny foil blanket at the finish line.

A gas is sealed in a syringe. Which statement explains why the gas exerts a pressure on the walls of the syringe?

Hand sanitiser gel feels cold on the skin as the alcohol in it evaporates. Which statement explains why evaporation makes the remaining liquid colder?

In a hospital ward, a patient's warm breath rises in the cooler air of the room. Why does warm air rise?

A sealed glass vial contains air. A technician in a hospital laboratory places the vial in a beaker of warm water.

A solar hot-water panel on a roof has a flat metal absorber plate with pipes attached. Water flows through the pipes to a storage tank above the panel.

Before a flight, a ground engineer pumps more air into an aircraft tyre. The volume of the tyre and the temperature of the air stay the same. Which statement explains why the pressure of the air in the tyre increases?

A farmer fits a solar water heater to a barn roof. The tank must absorb as much of the Sun's thermal radiation as possible. Which surface finish should the outside of the tank have?

Steel beams in an aircraft hangar roof are fitted with small expansion gaps. Which statement explains why a steel beam gets longer when it is heated?

An aircraft carries a sealed cylinder of oxygen gas. The volume of the cylinder is fixed.

A beekeeper melts beeswax and lets it cool. The temperature of a sample is recorded every 2 minutes.
Time / min: 0, 2, 4, 6, 8, 10, 12, 14
Temperature / °C: 78, 70, 64, 62, 62, 62, 57, 49

A cyclist leaves a sealed bicycle tyre in strong sunshine and the temperature of the air inside rises. Which statement correctly explains why the air pressure increases?

An archaeologist warms one end of a bronze rod in a flame. Which statement best describes how thermal energy is conducted along the rod?

Warm air rises above the servers in a data hall. What is the reason that warm air rises?

Replica bronze axe heads are made by pouring molten bronze into moulds, where it cools and solidifies.

A cyclist checks the air pressure in a sealed bicycle tyre.

A football is inflated by pumping extra air into it. The temperature of the air inside stays the same and the volume of the ball does not change. Why does the air pressure inside the ball increase?

On a hot day a steel railway track becomes slightly longer. Which statement explains this in terms of particles?

A railway company wants the roof of a carriage to absorb as little thermal radiation from the Sun as possible. Which roof surface is best?

A football is inflated by a pump at a sports club.

Long sections of steel railway track are laid in a country with hot summers and cold winters.

A sealed steel cylinder contains air. Which statement correctly explains how the air exerts a pressure on the walls of the cylinder?

A cyclist notices that the metal handlebar feels much colder to the touch than the plastic saddle, although both have been outside overnight and are at the same temperature. What is the reason?

Four identical metal cans are filled with the same volume of hot water at 80 °C and left in a cool room. The cans have different outer surfaces. Which can's water cools fastest?

Heat sinks in a data centre are made of copper and have thin vertical fins. A processor transfers thermal energy to the copper base of its heat sink, and warm air then leaves the fins.

Steel rails on a cycle-track bridge are laid in sections with small gaps between the ends of neighbouring sections.

A long steel rail on a library's rolling-ladder track is warmed by sunlight through a window and becomes very slightly longer. Which statement explains this?

At the edge of a swimming pool a metal handrail and a wooden bench have both been in the shade for hours and are at the same temperature, 20 °C. The metal feels much colder when touched. Which statement explains this?

A conservator in a library uses a wax that has a melting point of 54 °C and a boiling point of 280 °C. Which description applies to the particles of the wax at 120 °C?

In a library, a steel hot-water heating pipe runs along a wall for 30 m. When hot water is first pumped through, the pipe becomes longer.

An inflatable swimming ring is filled with air and sealed.

A sealed steel container of fixed volume holds a gas. The gas is heated. Which statement correctly explains why the gas pressure increases?

A box of fresh fish is packed in crushed ice. While the ice is melting, its temperature stays at 0 °C. Why does the temperature not rise?

A fish-processing plant stores compressed air in a sealed steel tank.

A winter jacket is filled with soft fibres that trap air.

In a fish-smoking oven, a heater at the bottom warms the air.

A cyclist grips a metal handlebar and a plastic grip. Both have been outside overnight at the same temperature of 5 °C, but the metal feels much colder. What is the reason?

The air in a bicycle tyre is heated by the sun on a hot day, and its pressure rises. Which statement explains this?

Archaeologists find a sealed ancient jar containing air. Which row describes the air particles in the jar?

Small gaps are left between sections of steel railway track. Why?

Archaeologists heat a sample of ancient beeswax in a laboratory.

A sealed syringe contains air. The plunger is pushed in so that the volume of the air is halved. The temperature of the air stays the same.
Which statement explains why the pressure of the air increases?

Steel railway lines are laid with small gaps between the sections. In hot weather the sections get longer.
Which statement describes what happens to the particles in the steel when its temperature rises?

A tank of water is heated by a heater at the bottom. The water at the bottom warms up and rises through the cooler water above it.
Why does the warmed water rise?

Steel railway lines are made in sections and laid end to end with small gaps between the sections.

A space telescope orbits the Sun in a vacuum. It has a shiny silver sunshield facing the Sun. The side of the telescope that faces away from the Sun is painted matt black.

A sealed steel container holds a sample of gas collected from a volcanic vent. The container is heated and its volume does not change. Which statement explains why the gas pressure increases?

A theatre lamp has a glass bulb containing an almost perfect vacuum. Energy from the hot filament reaches the glass wall mainly by which process?

In a theatre, warm air from the stage lights collects near the ceiling. Which statement gives the reason?

A technician is adjusting a theatre stage lamp that has been switched on for some time. The metal handle of the lamp is attached to a hot metal housing.

A volcanologist collects a sample of gas from a vent in a rigid sealed metal flask.

A sealed glass sampling flask of fixed volume holds air. It is left in strong sunshine on the deck of a research vessel and the air temperature rises. Which statement explains why the gas pressure rises?

On a cold morning a steel handrail and a wooden handrail on a footbridge are at the same temperature. The steel feels much colder to the touch. What is the reason?

Which finish on a flat roof would keep a building coolest in a hot, sunny climate?

A marine biology laboratory keeps tropical seawater in a tank. Some of the water evaporates and the vapour spreads through the room. The laboratory also stores air in a sealed steel cylinder of fixed volume.

An architect designs a house for a cold climate. The windows are double glazed, with a sealed layer of air between two sheets of glass.

A sealed glass vial of medicine contains only air. The vial is moved from a cold fridge to a warm room. Its volume does not change. Which statement explains why the pressure of the air in the vial increases?

An engineer touches a metal water pipe and a plastic water pipe. Both are at 10 °C but the metal pipe feels colder. Which statement explains this?

A long steel water pipe is fitted with expansion joints so that it does not buckle on hot days. Which statement describes what happens in the steel when the pipe is heated?

Which change would increase the rate at which water evaporates from the surface of an open reservoir?

A pharmacist handles medicines in three different states: a solid tablet, a liquid syrup and a gas in an inhaler can.

A volcanologist stands 6 m to one side of a glowing lava channel and feels her face grow warm. Which process mainly transfers thermal energy from the lava to her face?

A sealed canister of gas inside a theatre fog machine is warmed. Which statement explains why the gas pressure increases?

The mercury in a ship's engine-room thermometer rises up the tube as it is warmed. Which statement explains this?

A volcanologist studies a hot vent in a rocky crater floor.

Long steel pipes carry hot fluid along the deck of a ship.

On a cold morning, a person rests a bare hand on a metal handrail and on a wooden handrail of the same pier. Both rails are at the same temperature as the air. The metal rail feels much colder. Which statement explains this?

A warehouse in a hot climate needs a roof surface that keeps the building as cool as possible by absorbing the least thermal radiation from the Sun. Which finish is best?

A research vessel uses a liquid-in-glass thermometer to measure the temperature of seawater at different depths. The thermometer contains alcohol in a narrow glass tube.

A research station on a polar coast uses a solar panel to heat water. The panel is a flat metal plate with water pipes attached, facing the Sun.

A small paddling pool is heated by an electric heater placed at the bottom. Which statement explains why the warmed water moves upwards?

A rigid, sealed box of air in a library store is moved from a cool room into a warm room. The pressure of the air in the box increases. What is the reason?

On a cold day a technician touches a steel wind-turbine tower and a wooden door at the base. Both are at the same temperature, but the steel feels colder. Why?

A library keeps rare documents in a sealed, rigid metal box that contains air.

A heated hut at a wind farm has metal walls and a roof. A wind-turbine nacelle outside is painted white.

A sealed rigid metal flask of air is left in strong sunshine on a mountain ledge and its temperature rises. Which statement explains why the gas pressure inside the flask increases?

Which statement explains why metals are good conductors of thermal energy?

A chef heats 0.40 kg of oil from 20 °C to 160 °C. The specific heat capacity of the oil is 2000 J / (kg °C). How much thermal energy does the oil gain?

A mountaineer carries a sealed metal canister of gas for a camping stove.

A cook heats 0.25 kg of water in a pan. The water is heated from 18 °C to 98 °C. The specific heat capacity of water is 4200 J / (kg °C).

A vacuum flask keeps hot drinks hot. Which row correctly links a feature of the flask with the main energy transfer it reduces?

The cooling unit of an old-style refrigerator is placed at the top of the food compartment. Why is this the best position?

On a sunny day, the land near the coast warms up faster than the sea. Which statement describes the movement of air near the beach during the day?

A room is heated by a hot-water radiator fixed to the wall, just below a window. The house has cavity walls: two layers of brick with a gap between them.

A student looks through a microscope at smoke particles in a small glass cell filled with air. The smoke particles are lit from the side.
What does the student see, and what causes it?

A small glass cell is filled with air and a little smoke. The cell is lit brightly from the side and viewed through a microscope. The smoke particles appear as tiny bright specks.

A straight bimetallic strip is made by joining a strip of brass to a strip of iron. For the same temperature rise, brass expands more than iron.
What happens when the strip is heated?

Which statement is true for evaporation but not for boiling?

A car tyre is pumped up in the morning when the air temperature is 15 °C. By the afternoon, after driving on a hot road, the air inside the tyre is at 45 °C. No air leaks out of the tyre, and its volume stays almost constant.

Four identical metal cans each contain 200 g of water at 90 °C. Each can has a different outer surface. Which can cools fastest by thermal radiation?

A room heater is placed near the floor. Which statement correctly describes how it warms the air in the room by convection?

A bimetallic strip is made from a strip of brass joined firmly to a strip of iron of the same length. It is used as a switch in a fire alarm circuit.

Thermal radiation affects how buildings and containers gain and lose energy.

A solid sample is heated steadily by a heater and its temperature is recorded every minute. At 0, 1, 2, 3, 4, 5, 6, 7 and 8 minutes the temperatures are 30, 44, 58, 72, 72, 72, 72, 84 and 96 °C respectively.

Two blocks of equal mass receive the same quantity of thermal energy. Block X has a specific heat capacity of 400 J/(kg °C) and block Y has 1200 J/(kg °C). Which statement about their temperature rises is correct?

An athlete sweats on a warm day and feels cooler as the sweat evaporates. Which statement explains the cooling?

A sealed sports ball filled with gas is heated by the sun. When the gas is heated by the same amount, why does it expand much more than a similar-sized solid ball would?

A sealed capsule on a space probe contains helium gas. The volume of the capsule is fixed.

A sports hall has a heater mounted low on one wall. The walls are lined with foam containing trapped pockets of air.

A shop sells copper-based and glass saucepans. When both are placed on the same hot ring, the copper base warms much faster. Which statement explains this?

An engineer tests four identical metal plates in strong sunlight for a solar water heater. Each plate has a different surface finish. Which finish gives the greatest temperature rise in ten minutes?

A shop has a long steel rail fixed above its entrance. The rail is hotter on a summer afternoon than on a winter morning.

A cafe serves hot coffee in metal cups with a metal spoon. Customers hold the cups using a cardboard sleeve.

A cool box carries vaccines to a rural clinic. It has thick walls of polystyrene foam. Ice packs are placed inside the box.

A vacuum flask used by a farm worker keeps tea hot. There is a vacuum between the two glass walls. Why does the vacuum reduce thermal energy transfer by conduction and convection?

A musician touches a brass key and a wooden panel on a stage. Both are at 18 °C and the musician's hand is at 33 °C. The brass key feels colder. Which statement explains this?

A farmer grows tomatoes in a greenhouse. The Sun's energy warms the inside of the greenhouse.

A temperature switch in the cargo-hold heating system of an aircraft contains a bimetallic strip. The strip is made of a brass layer and an iron layer joined together. For the same rise in temperature, brass expands more than iron.

A technician in a concert hall tests two identical metal cans, one painted matt black and one polished silver. Each can is filled with 200 g of water at 85 °C and left in the same room. After 10 minutes the black can is at 52 °C and the silver can is at 63 °C.

The roof of a data-centre container is exposed to sunshine. Which finish on the roof would keep the container coolest?

An archaeologist heats a sample of beeswax steadily and records its temperature. The temperature rises, then stays constant at 62 °C for several minutes while the wax melts, and then rises again. Which statement explains the constant temperature?