thermal physics

• specific heat capacity

  the amount of energy needed to raise the temperature of 1kg of a substance by 1K
• absolute zero

  the lowest possible temperature an object can have
• the absolute zero is -273 degrees Celsius or 0 Kelvin
• when a substance changes state its internal energy changes but its kinetic energy and temperature stays the same
• specific latent heat

  the specific latent heat of fusion or vapourisation is the quantity of thermal energy needed to be gained or lost to change the state of a 1kg substance
• for a closed system, the total internal energy is constant assuming it isn't cooled or heated
• the internal energy of a body is the sum of the randomly distributed kinetic and potential energies of all its particles
• as the temperature of gas increases...

  • average particle speed increases
  • average kinetic energy of the particles increases
  • distribution curve becomes more spread out
• the temperature is the average energy per particle
• energy is constantly transferred between particles within a system through collisions, the internal energy of the system remains constant at these collisions but the individual energy of a particle changes
• at 0 kelvin all molecules have 0 kinetic energy
• the internal energy of a system can be increased by heating or doing work to transfer energy to the system
• the internal energy of a system can be reduced by cooling or doing work to remove energy from the system
• boyle's law

  • at a constant temperature the pressure and volume of a gas are inversely proportional
  • an ideal gas obeys boyle's law at all temperatures
• charles' law

  • at a constant pressure the volume of a gas is directly proportional to its absolute temperature
  • an ideal gas follows this
• the pressure law

  at constant volume, the pressure of an ideal gas is directly proportional to its absolute temperature
• the area under a pressure-volume graph is the energy transferred to change the volume of the gas
• for an ideal gas we can assume that all the internal energy is in the form of kinetic energy
• kinetic theory wasn't widely accepted until einstein was able to use kinetic theory to make predictions about brownian motion
• the scientific community only accepts new ideas when they can be independently validated
• brownian motion is the random motion of larger particles in a fluid caused by collisions with surrounding particles
• brownian motion contributed to the evidence for the existence of atoms and molecules
• brownian motion can be observed by looking at smoke particles under a microscope