Heat and Temperature

Heat and Temperature

1. Heat and Temperature

   • Heat is a measure of energy
   • Temperature is a measure of hotness
   • Energy flows from hot to cold

2. Kinetic Theory

   • Solids
     • Strong forces of attraction
     • Vibrate around fixed positions
       • Low energy
   • Liquids
     • Weaker forces of attraction
     • Move randomly
       • More energy
       • Slowly
   • Gases
     • Almost no attraction
     • Move randomly
       • Very fast
       • A lot more energy

3. Conduction

   • Occurs mainly in solids
   • CONDUCTION OF HEAT
     • Vibrating particles pass on kinetic energy to particles next to them
   • Metals are the best
     • Free electrons
   • Liquids and gases conduct heat much slower
     • No free electrons

4. Convection

   • Occurs in liquids and gases
   • CONVECTION CURRENTS
     • Particles with a lot of energy move to the cooler region, and take their heat with them

5. Heat Radiation

   • The emission of electromagnetic waves
   • Depends on the surface colour and texture
     • Dark, matte surfaces absorb and emit
     • Shiny, silvered surfaces reflect heat

6. Condensation and Evaporation

   • CONDENSATION
     • When a gas turns to liquid
     • Rate will increase if:
       • Temperature is lower
       • Windspeed is less
       • Temperature is lower
       • Density is higher
   • EVAPORATION
     • Liquid to gas
     • Rate will increase if:
       • Temperature is higher
       • Density is lower
       • Surface area is larger
       • Windspeed is greater

7. Rate of Heat Transfer

   • Depends on:
     • Surface area
     • Volume
     • Type of material
   • Limiting heat transfer