Transfer of Thermal Energy (Cambridge (CIE) IGCSE Co-ordinated Sciences (Double Award): Physics): Flashcards
Exam code: 0654 & 0973
1/340Still learning
Know0
What is meant by a good thermal conductor?
Was this flashcard helpful?
Cards in this collection (34)
What is meant by a good thermal conductor?
A good thermal conductor is a solid which easily transfers heat.
Define thermal insulator.
A thermal insulator (bad thermal conductor) is a solid which does not transfer heat well.
Almost all ______ are good thermal conductors.
Almost all metals are good thermal conductors.
Give two examples of materials that are bad thermal conductors.
Examples of bad thermal conductors include a wool blanket and layers of cardboard or paper. Non-metals and organic materials (from plants or animals) are often poor thermal conductors.
Convection is the main way that heat travels through ______ and ______.
Convection is the main way that heat travels through liquids and gases.
True or False?
Convection cannot happen in solids.
True.
Convection only occurs in fluids (liquids and gases). It cannot happen in solids because the particles are held in a rigid structure.
True or False?
Heat rises.
False.
Heat is not a substance, so it cannot rise. It is the hot liquid or gas that rises, and it is replaced by cooler fluid.
How is a convection current set up when a fluid is heated? (Extended Tier Only)
When a fluid is heated, the molecules vibrate and push each other apart, making the fluid expand and become less dense than its surroundings. The hot fluid rises, and cooler, denser fluid moves in to take its place.
True or False?
Convection currents form when a fluid is cooled. (Extended Tier Only)
True.
When a fluid is cooled, the molecules lose energy and collide less, so the fluid contracts and becomes more dense. The cold fluid falls, and warmer, less dense fluid moves into the space created. Both heating and cooling can create a convection current.
True or False?
All objects emit thermal radiation.
True.
All objects emit thermal radiation. The hotter an object is, the more thermal radiation it emits.
What type of electromagnetic wave is thermal radiation?
Thermal radiation is mainly infrared radiation.
True or False?
Thermal radiation requires a medium to travel through.
False.
Thermal radiation is an electromagnetic wave, so it can travel through a vacuum. It is the only way in which heat can travel through a vacuum.
True or False?
The colour of an object affects its ability to emit and absorb radiation.
True.
The colour of an object does affect its ability to emit and absorb thermal radiation.
What colour surface is the best emitter of thermal radiation?
Black surfaces are the best emitters of thermal radiation.
True or False?
White surfaces are good emitters and good absorbers of thermal radiation.
False.
White surfaces are poor emitters and poor absorbers of thermal radiation.
True or False?
Shiny surfaces are very good emitters of thermal radiation.
False.
Shiny surfaces are very poor emitters of thermal radiation. They are also very poor absorbers because they reflect the infrared radiation.
What is the aim of the experiment investigating thermal radiation from different surfaces? (Extended Tier Only)
The aim is to investigate how the amount of infrared radiation absorbed or radiated by a surface depends on the nature of that surface.
In the investigation of thermal radiation using different coloured flasks, what are the independent and dependent variables? (Extended Tier Only)
Independent variable = colour of the flask
Dependent variable = temperature of the water
Name two control variables in the investigation of thermal radiation using different coloured flasks. (Extended Tier Only)
Any two from:
Identical flasks (except for their colour)
Same amount of hot water
Same starting temperature of the water
Same time interval
True or False?
The colour of a flask affects the energy transferred away from it by conduction and convection. (Extended Tier Only)
False.
Colour does not affect energy transferred by conduction and convection, so any difference in energy transferred away from each flask must be due to infrared radiation.
To compare the rate of energy transfer away from each flask, plot a graph of ______ on the y-axis against ______ on the x-axis and draw curves of best fit. (Extended Tier Only)
To compare the rate of energy transfer away from each flask, plot a graph of temperature on the y-axis against time on the x-axis and draw curves of best fit.
Give one way to reduce random errors in the investigation of thermal radiation using different coloured flasks. (Extended Tier Only)
Any one from:
Take repeated readings for each coloured flask
Read the values on the thermometer at eye level to avoid parallax error
Make sure the hole for the thermometer is not too big, so thermal energy does not escape through it
True or False?
If the Earth had no atmosphere, the surface temperature would remain the same as it is currently. (Extended Tier Only)
False.
If the Earth had no atmosphere, none of the radiation emitted by the Earth would be trapped and the surface temperature would be extremely low.
Define the greenhouse effect. (Extended Tier Only)
The greenhouse effect is the process by which greenhouse gases in the Earth's atmosphere absorb and re-emit the radiation emitted by the Earth, causing the surface temperature of the Earth to increase.
The temperature of the Earth depends on a balance between which two things? (Extended Tier Only)
The temperature of the Earth depends on a balance of:
Radiation from the Sun, which is absorbed by the Earth
Radiation emitted by the Earth
True or False?
The Earth receives thermal radiation from the Sun but does not emit its own thermal radiation. (Extended Tier Only)
False.
The Earth receives thermal radiation from the Sun and emits its own thermal radiation at the same time. Remember that all objects emit thermal radiation.
What happens to the surface temperature of the Earth if the concentration of greenhouse gases becomes too great? (Extended Tier Only)
The surface temperature of the Earth becomes too high, because more of the radiation emitted by the Earth is absorbed and re-emitted by greenhouse gases.
Name one example of a greenhouse gas. (Extended Tier Only)
Any one from:
Carbon dioxide
Water vapour
Give one everyday application of a good thermal conductor.
Any one from:
Metal pans, to heat food quickly
Metal radiators, to transfer heat from the water inside to the surrounding air quickly
Why do saucepans often have plastic handles?
Plastic is a bad conductor (an insulator), so the handle slows the thermal energy transferred to your hands.
Double-glazed windows use a layer of ______ to act as an insulator and slow the transfer of thermal energy out of a house.
Double-glazed windows use a layer of air to act as an insulator and slow the transfer of thermal energy out of a house.
How does a radiator use convection to heat a room?
The hot radiator transfers thermal energy to the air nearby
The particles of this hot air spread out, making it less dense, so the hot air rises
Cold air replaces the hot air and is heated by the radiator in turn
The newly heated air also rises, then cools and sinks as it contracts and increases in density
True or False?
A black car becomes hot to the touch on a sunny day mainly because of convection.
False.
Energy from the Sun is transferred to the car by thermal radiation. The car is black and therefore a good absorber of thermal radiation.
Why does your hand feel hotter as you move it closer to a flame?
The increase in temperature is mostly caused by an increase in the amount of thermal radiation absorbed by your hand (convection has a much smaller effect).
Sign up to unlock flashcards
or