What is infrared radiation and how can we detect it?
Infrared radiation comes from infrared waves in the electromagnetic spectrum (next to visible red light). We detect it when we feel heat.
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What objects emit infrared radiation?
All objects emit infrared radiation. The hotter the object the more infrared radiation emitted.
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What surfaces are the best emitting and absorbing infrared?
Matt, black surfaces.
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What surfaces are the best reflectors of infrared?
Light, shiny surfaces.
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What are the particle formations of solids, liquids and gases?
In solids, the particles are in fixed positions. In liquids the particles are touching but can move. In gases, particles are separate and move fast and randomly in all directions.
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Which state of matter is the best conductor and why?
Solids as the particles are closest which allows energy to be transferred easily.
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What material is the best conductor?
Metals as they contain free electrons which allow the energy to be passed on very quickly.
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In which states of matter does convection occur?
Liquids and gases as they are fluids therefore able to move.
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How to convection currents work?
When heated, fluids expand and become less dense so they rise. This is replaced by cooler fluid, resulting in a convection current.
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What happens to the temperature of a liquid after evaporation and why?
Evaporation has a cooling effect on liquids as when the most energetic molecules escape from the liquid the average kinetic energy decreases, resulting in a drop in temperaature.
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What 3 things increase the rate of evaporation?
Increased surface area of the liquid, increased temperature of the liquid and a draught of air across the surface of the liquid.
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What 2 things increase the rate of condensation?
Increased surface area, decreased temperature of the surface area.
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What 4 things does the rate of energy transfer depend on?
The shape of the object, the materials the object is in contact with, the surface area of the object and the temperature difference between the object and its surroudings.
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How can we maximise the rate of energy transfer to keep things cool?
Use materials that are good conductors and painted black and have the air flow around them maximised.
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How can we minimise energy transfer to keep things warm?
Use materials that are good insulators and are white and shiny and prevent convection currents by trapping air in small pockets.
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What is specific heat capacity?
Specific heat capacity measures the amount of energy needed to raise the temperature of 1kg of a substance by 1°C.
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What equation is used to measure energy transfer?
Energy transfer = mass x specific heat capacity x change in temperature (e=mcθ)
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What are u-values?
U-Values tell us how much energy passes through a material each second. The lower the u-value the better the insulator.
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How do solar heating panels work?
Solar heating panels contain water which is heated by the sun. This can heat buildings or be used as domestic hot water. They are cheap to run but expensive to buy and install and water isn't heated at night.
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Other cards in this set
Card 2
Front
What objects emit infrared radiation?
Back
All objects emit infrared radiation. The hotter the object the more infrared radiation emitted.
Card 3
Front
What surfaces are the best emitting and absorbing infrared?
Back
Card 4
Front
What surfaces are the best reflectors of infrared?
Back
Card 5
Front
What are the particle formations of solids, liquids and gases?
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