THERMAL ENERGY

THERMAL ENERGY

1. Effects of thermal energy

   • Effects on matter
     • Solids expands and contracts the least followed by liquid then gas.
     • When cooled, solids, liqiuds and gases contract and decrease in volume.
     • When heated, solids, liquids and gases expand and increase in volume
   • Effects on everyday life
     • Problems
       • Laboratory glassware cracking when heated due to uneven expansion
       • Telephone and electrical wires snapping on cold days due to contraction
       • MRT and railway tracks wrap on hot days due to expansion
       • Bridges cracking on hot days due to expansion
       • Tiled and concrete pavements cracking on hot days due to expansion
       • Water pipes cracking or bursting on hot days due to expansion
     • Solutions
       • Water pipes are built with expansion bends to allow space for espansion
       • Laboratory glassware is made of Pyrex glass which expands very little when heated
       • Telephone and electrical wires are hung loosely to allow space for contraction
       • Bridges are built with rollers on one side to allow expansion
       • Pavements and tiles have expansion gaps that allows space for expansion

2. Transfer of thermal energy

   • Conduction
     • Conduction is the process of thermal energy transfer through a medium from one particle to another
     • All matters are conductors of thermal energy
     • Solids are generally better conductors of thermal energy as compared to liquid and gas
   • Convection
     • Convection is the process in which thermal energy is transmitted by the movement of liquid or gas. It cannot occur in solid
     • Occurs through a convection current
   • Radiation
     • Radiation is the process in which thermal energy is transferred by electromagnetic waves. It does not require a medium, thus it can occur in a vacuum
     • Factors that affect rate of radiation
       • Nature of the surface of the body; colour, reflectivity and texture. Surfaces which are dark in colour, matte and rough are better radiators of heat compare to surfaces which are light in colour, shiny and smooth

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