Flashcards by , created about 5 years ago


Created by x_clairey_x about 5 years ago
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Question Answer
Which objects absorb and emit infrared radiation? All objects emit and absorb infrared radiation
what makes an object radiate more infrared radiation? How hot it is, the hotter the object the more infrared radiation it radiates
What type of surface is perfect for emitting and absorbing infrared radiation? Dark, matt surfaces are good at absorbing and emitting infrared radiation.
what makes a bad surface for emitting and absorbing infrared radiation? Light, shiny surfaces are bad at emitting and absorbing infrared radiation.
What sort of surface would be good at reflecting infrared radiation? Light, shiny surfaces
What does a fluid do when heated? Expands, becomes less dense, rises and causes circulation (convection)
Infrared radiation is transfer of energy by what type of wave? Electromagnetic waves
What are all materials made out of? particles
What are the best conductors of energy? Metals
What materials are the best insulators? Wool and fibreglass
How does conduction take place? free electrons transfer energy inside metals
Why are non metals not good at conducting? They don't have free electrons
What is convection? The circulation of a fluid (liquid or gas) caused by heating it
What is evaporation? When a liquid turns into a gas
What is condensation? When a gas tuns into a liquid
How does evaporation cause cooling? The faster moving-molecules escape from the liquid
How can evaporation be increased? -Increase the surface area of the liquid -Increase the temperature of the liquid -Create a draught of air across the liquid's surface
How can condensation on a surface be increased? -Increase the area of the surface -Reduce the temperature of the surface
What does the rate of energy transfer to or from an object depend on? -The size, shape and type of material of the object -The materials the object is in contact with -The temperature difference between the object and its surroundings
How will the mass of an object change how quickly the temperature changes when heated? The greater the mass, the slower the temperature increases.
What does the rate of a substance's temperature change depend on when it is heated? -The energy supplied to it -Its mass -Its specific heat capacity
What is specific heat capacity? The energy required to raise 1kg of a substance by 1 degree Celsius
How do you work out specific heat capacity? c= E ------- m x (theta) E=Energy transferred (J) m=Mass (kg) c= Specific head capacity (j/kg oC) theta=temperature change (oC)
How can energy transfer be reduced in our homes? -Loft insulation -Cavity wall insulation -Double Glazing -Draught excluders -Aluminium foil behind radiators
What does a U-Value tell us? How much energy per second travels through a material.
What does a low U-Value mean? The material is a good insulator
What does a high U-Value mean? The material is bad at insulating