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Dr. Iffic Lecture 2

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FIRE!

FIRE!

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    Dr. Iffic Lecture 2 Dr. Iffic Lecture 2 Presentation Transcript

    • DR.  IFFIC:  FIRE!  
    • Hello  and  welcome  to  our  second  lecture.    Last  :me,  we  reviewed  the  four   fundamental  forces  of  the  universe  and  sorted  out  the  roman:c  life  of   protons  and  electrons.    Dmitri  Alekseyevich,  what  ques:ons  have  arrived   from  the  clamoring  masses  of  adulatory  knowledge  seekers?   We  have  a  ques:on  from  an  individual   purpor:ng  to  be  named  “Jimmy,”  who  asks,   “Dr.  Iffic,  what  exactly  is  fire?”    
    • NOT  “JIMMY”  AT  ALL.   “Jimmy,”  eh?    A  likely  story.    Very  well,  “Jimmy.”    The  nature  of  fire  is  not  quite   as  tripped-­‐out  crazy  as  you  may  imagine,  but  in  order  to  understand  fire,  you   must  first  understand  heat.    And  heat,  in  a  word,  is  jiggling.     Jiggling?    
    • JIGGLING,  Dmitri  Alekseyevich.    Pure  and  simple.     Do  you  mean  to  say  that  if  I  jiggle  this  nonbranded  toaster   pastry,  it  will  become  warm  and  delicious?   Well,  it  is  already  delicious.    But  the  heat  of  the  nonbranded   toaster  pastry  is  not  determined  by  the  jiggling  of  the  en:re   pastry.    It  is  determined  by  the  jiggling  of  each  and  every   individual  molecule  within  the  pastry.    That  is  what  heat  energy  is   –  the  jiggling  of  molecules.    
    • And  molecules  are  :ny  lile  bits  of  something,  is  that  right?     More  or  less.    Molecules  are  collec:ons  of  atoms  that  are  stuck  together  very  :ghtly   because  of  what  their  electrons  are  doing.    And  molecules  are  always  jiggling  back  and  forth   to  some  degree.    The  jiggling  is  so  small  that  we  can’t  see  it.    But  we  can  sense  it,  and   observe  it,  as  heat.    Hot  molecules  are  jiggling  fast.    Cold  molecules  are  jiggling  slower.     atom   atom   atom   atom   atom   MOLECULE   Cold  =  slow   Hot  =  fast  
    • It’s  strange  to  think  that  my  pastry  will  jiggle  once  I  toast  it.     It  is  jiggling  already,  Dmitri  Alekseyevich.    It  is  at  room  temperature,  which  requires  a  certain   amount  of  jiggling.    If  you  put  it  in  the  freezer,  it  would  jiggle  slower,  but  there  would  s:ll  be   some  jiggling  going  on.    In  theory,  if  your  pastry  stopped  jiggling  altogether,  it  would  be  at   absolute  zero  temperature  –  but  it’s  impossible  to  stop  all  the  jiggling  in  a  molecule.     Incredible  jiggling   Intense    jiggling   Moderate  jiggling   Very  lile  jiggling   Absolutely  no  jiggling  
    • If  heat  is  just  jiggling,  why  does  it  hurt  to  touch  something  hot?     The  cells  in  your  body  can’t  operate  correctly  when  they’re  jiggling  too  fast.    And  when   cells  can’t  operate  correctly,  they  die.    So  when  your  nerves  sense  that  the  jiggling  is   geang  to  dangerous  levels,  they  send  a  message  to  your  brain  saying,  HOOLABALOOLA!     GET  YOUR  HAND  OFF  THAT  HOT  THING,  YOU  CELL-­‐KILLING  IMBECILE!    The  fact  that  heat   is  jiggling  doesn’t  mean  it’s  no  big  deal  –  too  much  jiggling,  or  not  enough  jiggling,  is   very  dangerous  for  living  things.    
    • For  example,  fire.     For  example,  fire,  indeed.    Fire  will  jiggle  you  to  a  crisp   before  you  can  say,  HOOLABALOOLA!    And  what  use   will  your  nonbranded  toaster  pastry  be  to  you  then?    
    • So  what  IS  fire?     Fire  is  actually  gas  that  is  jiggling  so  fast  that  it  glows.     Jiggling  can  make  something  glow?    
    • Yes  indeed.    You  see,  the  jiggling  energy  that  is  heat  does  not  stay  in  one   place.    It  has  a  tendency  to  spread  out  as  much  as  possible.    One  way  it   spreads  out  is  when  molecules  touch  each  other.    The  faster-­‐jiggling,  hoer   molecules  transfer  some  of  their  jiggling  energy  to  the  slower-­‐jiggling,   colder  molecules,  un:l  everything  is  jiggling  the  same  amount.     That  makes  sense.    
    • Also,  molecules  can  reduce  their  jiggling  energy  by  shoo:ng  out  a   photon,  or  absorb  a  photon  and  transform  it  into  jiggling  energy.    
    • OK,  that’s  a  lile  weird.    Isn’t  a  photon  just  a   :ny  lile  par:cle  of  light?     Well,  essen:ally  it  is,  although  it  acts  like  a  wave  too,  which  is   one  of  the  more  tripped-­‐out  crazy  aspects  of  science.       So  super-­‐hot  things  start  shoo:ng  out  photons?     Not  just  super-­‐hot  things,  Dmitri  Alekseyevich.    You  and  your   nonbranded  toaster  pastry  are  shoo:ng  out  photons  right  now,   and  absorbing  photons  that  got  shot  out  from  other  things.    
    • But  I’m  not  glowing!    Nor  is  my  nonbranded  toaster  pastry!     Remember,  Dmitri  Alekseyevich,  not  all  photons  are  visible  to  our  eyes.    Radio   waves,  microwaves,  and  gamma  rays  are  all  made  of  photons,  but  we  can’t  see   them,  even  though  we  can  use  them  to  transmit  informa:on,  cook  frozen  burritos,   and  turn  people  into  the  Hulk.    Because  photons  behave  like  waves,  they  have   frequencies,  and  different  frequencies  create  different  forms  of  radia:on.     Radio  Waves   Microwaves   Gamma  Rays  
    • Think  of  the  strings  on  a  guitar.    If  you  play  them  at  one  set   of  frequencies,  you  get  Mary  Had  a  Lile  Lamb.    
    • whereas  if  you  play  them  at  another  set  of  frequencies,  you  get  the   latest  hit  by  the  Icelandic  death  metal  band  Sküllmelter.       Similarly,  while  photons  at  one  frequency  produce  a  beam  of  yellow   light,  at  a  different  frequency  they  produce  microwaves.    
    • So  what  frequency  are  the  heat-­‐related  photons  coming  out  of  me  and  my  nonbranded   toaster  pastry?     They  are  at  the  infrared  frequency,  which  is  the  frequency  of  most  heat-­‐related   photons,  and  which  is  invisible  to  us,  unless  we  are  commandos  with  super  cool   thermal  imaging  goggles.     OK,  so  why  can  we  see  fire?    
    • Fire  is  made  of  gas  that  is  so  superhot  that  it  is  also  spiang  out  photons  that  we  can  see.    When   burnable  stuff  gets  hot  enough,  its  molecules  jiggle  so  fast  that  they  fly  apart  into  plain  old   atoms.    For  example,  wood  is  made  of  organic  molecules  that  include  carbon,  oxygen,  and   hydrogen.    Here’s  a  diagram  that  shows  where  the  atoms  are  and  how  they  are  bonded  together.   H   H   H   lots   more   C   C   stuff   C   C   O   H   lots  more  stuff   H   When  these  molecules  fly  apart,  the  carbon  atoms  interact  with  the   oxygen  molecules  in  the  air  to  form  carbon  dioxide.   O   O   O   H   C   C   H   O   C   H   O   H   C  
    • And  when  carbon  atoms  join  with  oxygen  molecules  to  make  carbon  dioxide,  it  creates  a   tremendous  extra  kick  of  jiggling  heat  energy.    So  the  superhot  carbon  dioxide  molecules  shoot   out  all  kinds  of  photons,  including  red,  yellow,  or  blue  ones  that  we  can  see.     O   O   C   C   O   O   They  also  float  upwards,  because  hot  gases  tend  to  float  on  top  of  cool  gases.    But  as  they  float,   they  cool  down.    Prey  soon  they  cool  down  enough  so  that  they  are  no  longer  shoo:ng  out   visible  photons,  just  the  invisible  infrared  ones  that  everything  shoots  out.     O   C   O   O   C   O   O   C   O  
    • Including  my  nonbranded  toaster  pastry.   Correct.       So  how  can  fire  jump  from  one  burning  thing  to  another  if  it’s  just  gas?     It’s  not  really  jumping.    The  superhot  glowing  gas  is  so  hot  that  if  another  chunk  of   burnable  stuff  gets  too  close,  its  own  carbon  molecules  will  heat  up,  fly  apart,  and   start  making  their  own  superhot  glowing  gas.       H   H   H   O   O   lots   O   more   C   C   H   C   C   stuff   H   O   O   C   C   O   H   C   H   lots  more  stuff   H   H   C   O   O   C   C   O   O  
    • So,  to  recap:  fire  is  superhot  glowing  gas,  heat   is  jiggling,  and  my  nonbranded  toaster  pastry   and  I  are  constantly  shoo:ng  out  and   absorbing  invisible  photons.   Correct  in  every  respect.    Now  let  us  bombard   your  nonbranded  toaster  pastry  with  photons   un:l  it  jiggles  at  a  more  delicious  rate.