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Energy, Thermodynamics

energy - ability to do work or transfer heat  

  • force - any type of push/pull placed on an object
  • work - energy used to make an object move against a force
    • work = force x distance
  • heat - energy transferred from hotter object to colder one
  • kinetic energy - energy of motion
    • Ek = 1/2 mv2
    • thermal energy - from kinetic energy of molecules in a substance
  • potential energy - energy based on relative position
    • Ep = mhg, where g = 9.8 m/s2 (gravitational constant)
    • chemical energy - from potential energy in bonds
  • electrostatic energy - interactions w/ charged particles; form of potential energy
    • Eel = (kQ1Q2) / d
    • positive when 2 charges repel each other, negative when attracting each other
  • joule - SI unit for energy
  • calorie - amount of energy required to raise temperature of 1g of water by 1°
    • 1 calorie = 4.184 joules
    • 1 Cal = 1 nutritional calorie = 1000 calories = 1 kcal

internal energy - sum of all kinetic/potential energy in a system  

  • 1st law of thermodynamics - energy is conserved, moves between system/surroundings
  • numerical value of E can't be found, only change in E (DE)
  • DE = Efinal - Einitial
  • DE negative when energy lost (exothermic)
  • DE positive when energy gained (endothermic)
  • DE = q + w
    • q positive when heat moves from surroundings into system, negative when heat moves from system into surroundings
    • w positive when surroundings work on system, negative when system works on surroundings

system - area isolated for study  

  • surroundings - everything other than the system in question
  • closed system - can exchange energy but not matter w/ surroundings

state function - property of system determined by its condition/state  

  • doesn't depend on how a change is carried out
  • examples of state functions - E, DE
  • not examples of state functions - work, heat
Subject: 
Chemistry
Subject X2: 
Chemistry

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