# Physics : Energy transfer by heating

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• Created by: Bexxmay
• Created on: 03-04-14 13:15
• Energy transfer by heating
• Can detect infrared radiation- it is warm against out skin
• Can travel through a vaccume - Sun
• Good emitters of infrared radiation
• Rough surface
• Light , shiny surfaces are good reflectors of infrared radiation
• Smooth surface
• States of Matter
• Solid
• Particles vibrate about fixed positions- has a fixed shape
• Liquid
• Particles are in contact but move about randomly , so doesnt have a fixed shape
• Gas
• Particles far apart and move randomly really fast. Doesnt have a fixed shape and can flow
• Conduction
• Mainly solids- good conductors
• Convection
• occurs in fluids
• when a fluid is heated, it expands , therefore becomes less dense and rises. the warm fluid is replaced by cooler , denser fluid.
• Resulting to a convection current transfers energy throughout the fluid
• Evaporation and Condensation
• Evaporation
• When a liquid turns into a gas. Energetic molecules escape from the liquids surface and enter the air. This is because they become too hot. As the energetic molecule touches a cold surface,it condenses and turns back into a liquid
• Condensation
• When a gas turns into a liquid. When a warm air molecule touches a cold surface, it turns into a liquid.
• Energy Transfer by design
• The Greater the temperature difference between an object and its surroundings, the greater the rate at which energy is transfered.
• -Materials the object is in contacts wtg
• - The objects shape
• - The objects surface area
• We want to minimise the rate of energy transfer to keep things warm. Reduce conduction, convection and radiation
• Need a cood insulator
• White , shiny objects
• Prevent conduction currents by trapping the air in small pockets
• Specific heat capacity
• SHC of a substance in the amount of energy required to raise the temperature
• The higher the SHC, the more enery required for each degree temperature change
• E = M x C x O
• E: energy transferred , J
• M: Mass , KG
• C: SHC, J/Kg
• O: temperature change,  C
• Heating and insulating Buildings
• Fibre glass: reduce energy transfer by conduction
• Cavity Walls: Traps air in small pockets to reduce energy transfer by convection
• Double Glazing: reduce energy transfer by condction
• Drought Proof: reduce energy transfer by convection