When metals are heated their free electrons gain kinetic energy and move through the metal transferring energy by colliding with other particles
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What are materials that are poor conductors called?
Insulators
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Why are wool and fibreglass the best insulators?
Because they contain trapped air
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What does convection occur in?
Fluids (liquids and gases)
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Why does a convection current happen when we heat a fluid
When a fluid is heated, it expands because the particles move further apart. The fluid becomes less dense because the same mass is filling a bigger space so therefore it rises
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What does the convection current do?
Transfer energy throughout the fluid
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What is evaporation?
When a liquid turns into a gas at the surface of the liquid
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Why does evaporation take place?
Because the more energetic liquid molecules escape from the liquid's surface and enter the air. Therefore the average kinetic energy of the remaining molecules is less so the temperature of the liquid decreases.
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What doe evaporation cause?
Cooling
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What is condensation?
When a gas turns into a liquid
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What do all objects emit?
Infrared radiation
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What happens when an object gets hotter?
It emits more infrared radiation in a given time
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What does short wavelength infrared radiation from the Sun do to the Earth
It passes through the Earth's atmosphere and heats the Earth
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Why do long wavelength infrared radiation warm the Earth up?
It is unable to pass through the Earth's atmosphere into space as it is absorbed by some gases
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What are the best absorbers of infrared radiation?
Dark, matt surfaces
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What are the best emitters of infrared radiation?
Dark, matt surfaces
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What are good reflectors of infrared radiation?
Light, shiny surfaces
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What does the rate at which energy is transferred depends on?
The greater the temperature difference between an object and its surroundings, the materials the object is in contact with, the object's shape and the object's surface area
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To maximise the rate of energy transfer to keep things cool, what materials do we use?
Ones that are good conductors, painted black and have the air flow around them maximised
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Other cards in this set
Card 2
Front
Why are metals the best conductors?
Back
When metals are heated their free electrons gain kinetic energy and move through the metal transferring energy by colliding with other particles
Card 3
Front
What are materials that are poor conductors called?
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