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sci chp 10 Transfer of Heat Energy & Its Effect - Coggle Diagram
sci chp 10 Transfer of Heat Energy & Its Effect
Temperature
Measure of how hot an object is
SI Unit: Kelvin (K)
Expansion & Contraction of Matter
Telephone wires/cables sag (contract in cold).
Concrete/tiles crack → expansion gaps prevent this.
Glass cracks with sudden hot water.
Pipes/bridges → bends or rollers for expansion.
Jar lids loosen when heated (metal expands faster).
Everyday Effects
Telephone wires/cables sag (contract in cold).
Concrete/tiles crack → expansion gaps prevent this.
Glass cracks with sudden hot water.
Pipes/bridges → bends or rollers for expansion.
Jar lids loosen when heated (metal expands faster).
Bimetallic Strip
Made of two different metals (e.g. Brass + Iron).
Metals expand/contract at different rates.
Brass expands more → strip bends.
Uses: thermostat (iron, oven, fridge, air-con, fire alarm, electric iron).
Methods of Heat Transfer
Conduction
Heat transfer without movement of medium.
Metals = good conductors.
Plastic, wood = poor conductors.
Uses: cooking pans (metal), plastic handles.
Convection
Heat transfer by movement of fluids.
Hot fluid: expands, less dense, rises.
Cold fluid: contracts, denser, sinks.
Examples:
Air-con (cold air sinks, hot air rises).
Kettle (hot water rises, cold sinks).
Sea/Land breeze.
Firefighters crawl (cooler air below).
Radiation
Heat transfer without medium.
Dark, dull, rough → good absorbers/emitters.
Light, shiny, smooth → poor absorbers/emitters.
Examples:
Silver kettles keep contents hot.
Light clothes/buildings stay cool.
Black fridge pipes release heat.
Vacuum Flask Design
Plastic stopper: reduces conduction + convection.
Silvered walls: reduce radiation.
Vacuum: no conduction/convection.
