Thermodynamics

• What is temperature?

  A measurement of the average kinetic energy of particles in an object or substance
• What is heat?

  The flow of energy from an object of a higher temperature to an object at a lower temperature
• What happens when heat is applied to a substance?

  The particles move more and take up more space(things expand when heated)
• Substance + heat=

  increase in temperature
• what does heat do to a substances AKE

  heat is the transfer of energy, heat increases the substances average kinetic energy
• increased average kinetic energy is seen by

  increase in temperature, change in state, expansion of substance
• Internal energy

  total potential kinetic energy in a substance. If enough heat is applied/removed a substance will have a change of state.

  
  

  -The energy associated with the random disordered motion of atoms and molecules
• potential energy formula 


  PE=mgh

  m=mass

  g=acceleration due to gravity

  h=height from ground
• Kinetic energy formula

  KE=1/2mv^2

  m=mass

  v=speed/velocity squared
• heat always move from

  hot object to cold object
• Why is the Celsius scale more commonly used rather than the kelvin scale

  The Celsius scale is more convenient as it is based on the properties of water and it easy to reproduce anywhere in the world
• What is the kelvin scale


  An absolute scale by which everything in the universe can be referred
• What is the celsius scale based on

  the melting and boiling points of water
• What is the kelvin scale based on

  The kinetic theory of matter where 0K corresponds to the lowest possible temperature such that particles completely stop moving
• Kinetic theory of matter

  All matter is made up of atoms or molecules in constant motion
• Solids


  particles have attractive and repulsive forces to keep it in a fixed postion.
• particles in a solid:

  vibrate around an average position
• Liquids


  particles take up the space of the container they are in and collide.
• Particles in liquids:

  have no fixed shape but a fixed volume
• Gasses


  particles are in constant random motion. Fill the volume of any container. Particles speed is high enough so they dont have a fixed volume
• Plasma


  exists when matter is heated to very high temperatures and atoms free electrons(ionisation). No fixed volume but shape has unique properties
• Zeroth law of thermodynamics

  when 2 objects are in thermal contact, energy will flow between them until thermal equilibruim is reached.
• First law of thermodynamics


  Energy cannot be created or destroyed, only transformed. The total energy in a system is constant.
• Internal energy formula

  ΔU=Q-W

  ΔU=change in internal temp(j)

  Q=heat added(j)

  W=work done by system(j)
• Specific heat capacity


  Amount of energy required to change the temperature of 1kg of a substance by 1 degree celsius
• Specific heat capacity formula

  Q=cmΔT

  Q=heat added/transferred(j)

  c=specfic heat capacity of material (jkg -1 K -1)

  m=mass(kg)

  ΔT=change in temperature(K or C)
• Latent heat of Fusion/Evaporation


  Amount of energy that must be added or removed from a material to change the materials state
• LH fusion/evap formula

  Q=mL

  Q=heat change added/removed(j)

  m=mass(kg)

  L=latent heat(jkg-1)
• LH fusion


  solid to liquid

  temp number increases

  extra energy used to reduce forced between particles
• LH evaporation


  Liquid to gas

  temp number increases

  extra energy used to break down intramolecular bonds
• Evaporation/cooling


  evaporation occurs when higher energy particles escape the surface of the liquid leaving the lower energy particles behind

  result=AKE and temp drops
• Conduction


  direct flow of heat through a material from physical contact
• Conduction can be affected by

  type of material, temperature difference, thickness and surface area
• Convection


  heat transfer between a surface and adjacent fluid(gas air or liquid) by the flow of fluid from one place to another
• Radiation


  The transfer of thermal energy through matter or space by electromagnetic waves at 3 X 10^8 ms-1

  EMR is emitted by all objects above absolute zero
• Heating curve

  Solid

  GAS

  -boiling/condesing-

  LIQUID

  -melting/freezing-

  SOLID