Thermal

Thermal

1. Concepts

   • Temperature and heat flow
     • Hot/Cold identify direction in which thermal energy is transferred
     • temperature of an object is a measure of how hot it is
       • temperature difference determines the direction of natural transfer of thermal energy
     • thermal energy naturally transferred down
     • two objects would be expected to reach the same temperature therefore in thermal equilibrium
     • thermal energy refers to the non-mechanical transfer of energy between a system and its surroundings

2. heat and internal energy

   • kinetic theory
     • phase of substance e.g. solid, liquid, gas
   • Internal Energy
     • molecules have kinetic energy as they are moving
       • translational
       • rotational
     • potential energy due to intermolecular forces
     • total energy of molecules is the internal energy
     • Temperature is a measure of the average kinetic energy of the molecules in a substance

3. Specific heat capacity

   • if an object could be heated up with no energy loss then the increase in temperature depends on three things energy mass and substance
   • thermal capacity of an object is the energy required to raise its temperature by 1K
   • specific heat capacity is the energy required to raise a unit mass of a substance by 1k
   • if an objects temp raised above room temperature it starts to lose energy more quickly
   • same amount of energy required to raise a temperature of an object
   • method of mixtures
     • measure the masses of liquids ma and mb
     • measure the two starting temperatures
     • mix two liquids together
     • record max temperature
     • if no energy is lost
       • energy lost by hot substance cooling down = energy gained by cold substance heating up
       • changes in temperature of the apparatus

4. states of matter and latent heat

   • when a substance changes phase the temperature remains constant even though thermal energy is still being transferred
   • amount of energy associated with phase change is called the latent heat
   • fusion- solid to liquid
   • vaporization- liquid to gas
   • potential energy increases
   • bonds are being broken which requires energy
   • bonds being made releases energy
   • specific latent heat of a substance is defined as the amount of energy absorbed or released during a phase change
   • measuring vaporization of water
     • amount of energy provided to water at boiling is calculate using E=IVt
     • mass vaporized needs to be recorded
       • specific latent heat = IVt/(m1-m2)
   • measuring fusion of water
     • provided we know the specific heat capacity of water we can calculate the specific latent heat of fusion of water
     • energy lost by water cooling down= energy gained by ice