Define thermal conduction. (Extended Tier Only)
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Define thermal conduction. (Extended Tier Only)
Thermal conduction is the transfer of thermal energy through a substance.
True or False?
Thermal conduction in solids occurs when hotter, more energetic atoms or ions vibrate faster and collide with neighbouring atoms or ions. (Extended Tier Only)
True.
Thermal conduction in solids occurs when hotter, more energetic atoms or ions vibrate faster and collide with neighbouring atoms or ions, transferring energy throughout the structure of the solid.
Why does thermal conduction generally occur faster in metals than non-metals? (Extended Tier Only)
Thermal conduction occurs faster in metals because metals have free (delocalised) electrons, which speed up the energy transfer throughout the substance.
When does thermal conduction end? (Extended Tier Only)
Thermal conduction ends when thermal equilibrium is reached.
Define thermal equilibrium. (Extended Tier Only)
Thermal equilibrium is a state in which no net energy transfer takes place because a consistent temperature has been reached.
True or False?
Thermal conduction does not happen in liquids or gases because the particles are too far apart. (Extended Tier Only)
False.
Thermal conduction does happen in liquids and gases, but they tend to be poor conductors because the particles are further apart than in solids.
True or False?
Convection cannot happen in solids.
True.
Convection only happens in liquids and gases because the particles are free to move around. It cannot happen in solids because the particles are held in a rigid structure.
How is a convection current set up when a fluid is heated?
When a fluid is heated, the space between particles increases, so the density of the fluid decreases which causes it to rise, and cooler, denser fluid takes its place.
In a convection current hot fluid expands and rises. What is this replaced by?
In a convection current hot fluid expands and rises. In a convection current, this is replaced by cooler, denser fluid.
What substance is used as a purple dye to demonstrate convection in water?
Potassium permanganate is used as a purple dye to demonstrate convection in water.
True or False?
Heat rises.
False.
Heat is not a substance so it cannot rise. It is the heated region of the fluid that rises as its density decreases.
True or False?
Convection currents form when a fluid is cooled.
True.
When a fluid is cooled, the movement of the particles slows down and they come closer together increasing the density. The denser fluid sinks and less dense fluid takes its place.
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.
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.
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.
What type of electromagnetic wave is thermal radiation?
Thermal radiation is infrared radiation.
In terms of the rate of energy transfer, how does an object maintain a constant temperature? (Extended Tier Only)
An object maintains a constant temperature when the rate of energy transfer away from the object is equal to the rate of energy transfer to the object.
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?
When an object emits less thermal radiation than it absorbs, its temperature increases. (Extended Tier Only)
True.
When an object emits less thermal radiation than it absorbs, its temperature increases.
What colour surface is the best emitter of thermal radiation?
Black surfaces are the best emitters 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.
True or False?
When an object emits more thermal radiation than it absorbs, its temperature increases. (Extended Tier Only)
False.
When an object emits more thermal radiation than it absorbs, its temperature decreases.
True or False?
If the Earth had no atmosphere, the temperature on the surface would remain the same as it is currently. (Extended Tier Only)
False.
If the Earth had no atmosphere, the temperature on the surface would drop to about −180 °C at night, the same as that of the Moon at night.
Define the Greenhouse Effect. (Extended Tier Only)
The Greenhouse Effect is the process by which certain gases in the Earth's atmosphere trap and reradiate infrared radiation, leading to an increase in the temperature of the Earth's surface.
What are the factors affecting the Earth's temperature? (Extended Tier Only)
The factors affecting the Earth's temperature are the rate of reflection, absorption, and emission of light and infrared radiation from the Sun.
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. Remember that all objects emit thermal radiation.
Define Greenhouse Gases. (Extended Tier Only)
Greenhouse gases are gases in the atmosphere that absorb and reradiate longer-wavelength infrared radiation emitted by the Earth, preventing it from escaping into space, and causing warming of the Earth's surface.
How does the Greenhouse Effect cause warming of the Earth's surface? (Extended Tier Only)
The Greenhouse Effect causes warming of the Earth's surface because of the Sun's thermal radiation reaching the Earth's atmosphere. Here some radiation is reflected back into space, and the rest is absorbed and reradiated by greenhouse gases, warming the atmosphere and Earth's surface.
What is an example of a greenhouse gas? (Extended Tier Only)
Examples of greenhouse gases are:
carbon dioxide
methane (natural gas)
water vapour