CORE PHYSICS AQA

CORE PHYSICS AQA

1. ENERGY

   • HEAT RADIATION
     • Heat is transferred in three different ways; radiation, conduction, or convection.
     • Infrared radiation is the emission of elecromagnetic waves
     • Radiation depends on an awful lot on surface colour and texture
   • KINETIC ENERGY AND CONDUCTION
     • Kinetic energy can explain three states of matter
     • Conduction of heat occurs mainly in solids
     • Metals are good conductors because of their free electrons
   • CONVECTION
     • Convection of heat - liquids and gases only
     • CONVECTION CURRENTS are all about CHANGES IN DENSITY
   • CONDENSATION AND EVAPORATION
     • Condensation is when gas turns to liquid
     • Evaporation is when liquid turns to gas
     • Rates of Evaporation and Condensation can vary
       • THE RATE OF EVAPORATION/CONDENSATION WILL BE FASTER IF:
         • EVAPORATION
           • Temperature is higher
             • The average particle energy will be higher, so more particles will have enough energy to escape
           • Density is lower
             • The forces between the particles will usually be weaker, so more particles will have enough energy to overcome these forces and escape the liquid
           • Surface area is higher
             • More particles will be near enough to the surface to escape the liquid
           • Airflow over the liquid is greater
             • The lower the concentration of an evaporating substance in the air it's evaporating in to, the higher the rate of evaporation
               • A greater airflow means air above the liquid is replaced more quickly, so the concentration in the air will be lower
         • CONDENSATION:
           • Temperature of the gas is lower
             • The average particle energy in the gas is lower, so more particles clump together and form liquid droplets
           • Temperature of the surface the gas touches is lower
           • Density is higher
             • The forces between these particles will be stronger. Fewer particles will have enough energy to overcome these forces and will instead clump together to form a liquid
           • Airflow is less
             • The concentration of the substance in the air will be higher, so the rate of condensation will be lower