thermo 1

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thermo 1
2013-01-23 10:58:17
chem thermo

thermo 1
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  1. Energy
    • measure of a system's ability to do work
    • units are joules (J)
    • diff forms
  2. Heat
    • form of kinetic energy
    • Thermal energy (how much kinetic energy the substance has) is the kinetic energy possessed by atoms or molecules moving with random motion within
    •  symbol is Q units joules (J). 
  3. Temperature
    • measure of the average kinetic energy of its atoms or molecules. 
    • SI units are Kelvin (K). common units celsius
  4. kinetic molecular theory (KMT)
    • states that everything is made of tiny particles atoms or molecules
    • empty spaces between the particles & distance between particles is large compared to their size. 
    • in constant motion and motion increases with state changes from solid to liquid to gas. 
    •  solid are held close together by strong attractive forces; vibrate but cannot move around independently. 
    • liquid are held together more loosely by weaker attractive forces; the particles can move around, colliding into other particles and into the container walls
    • collisions are perfectly elastic, meaning that particles do not lose kinetic energy by colliding with each other.
    •  If heat is added to a substance, its particles gain energy and move faster.
    • e.g. applications sidewalks/bridges
  5. conversion kelvin to celsius and vice versa
    • celsius -> kelvins, +273.15
    • kelvins -> celsius, -273.15
  6. Enthalpy
    energyof a system which is the sum of the heat (E), and the pressure-volume product(PV). H = E + PV
  7.  system
    • system is surrounded by a boundary which separates the system from its surroundings. 
    • state of the system = description of the system in terms of its fundamental properties: temperature, composition, pressure and volume. 
  8. change in enthalpy
    • enthalpy of products – enthalpy of reactants
    • heat absorbed when the reaction takes place under constant applied pressure. 
    • units are kJ/mol
    • exothermic reactions, heat is released and ΔH is negative (ΔH < 0).  
    • endothermic reactions heat is absorbed and ΔH is positive (ΔH > 0).
  9. calorimeter
    instrument used to study the heat of reaction and the change in enthalpy for reactions with no pressure-volume changes. 
  10. substance's specific heat capacity
    •  capacity to absorb or release heat. 
    • -quantity of heat needed to raise the temperature of 1 kg of a substance by 1°C.
    • -symbol is c and units are J/(kg•°C).
    • -other units used are cal/(g•°C)
  11. water C
    4.18 J/(g•°C) or 4.18 kJ/(kg•°C)
  12. Q = mcΔT
    • Q = amount of heat transferred (in J)
    • m = mass of substance (in g)
    • c = specific heat capacity (in J/(g•°C))
    • ΔT = temperature change (in °C)
    • = Tfinal - Tinitial
  13. changing states
    • energy required was used to break the bonds which held the ice in a solid state.   
    • ice absorbs energy, and liquefies b/c gains 3 types of energy: translational energy, rotational energy, and vibrational energy. 
  14. 3 types of kinetic energy (molecular motion)
    • translational energy is the type of kinetic energy due to the movement of the whole molecule (this movement is short range and erratic among molecules due to the frequency of collisions with other molecules)   
    • Vibrational energy is due to the oscillation
    • or deformation of the bonds within the molecule.
    • Rotational energy is due to the entire molecule rotating
  15. if temperature increases in a reaction
    = heat was released and the ∆H is negative
  16. Endothermic 
    energy absorbed is in the form of heat
  17. Exothermic 
      energy released is in the form of heat
  18. Four Laws of Thermodynamics
    • 1. First law of thermodynamics (Law of Conservation of Energy)
    • all processes tt happen in an isolated system-> energy of the system = constant.   
    • energy cannot be created or destroyed, only transformed from one form to another
    • 2. Second law of thermodynamics  
    • heat always flows from hot objects to cold objects, never other way around      
    • Energy cannot be transformed from one form to another without a loss of useful energy.    
    • work in -> work out + heat, more useful energy to less useful energy (usually heat)
    • 3. Third law of thermodynamics
    • The entropy (a measure of a system's disorder) of a perfect crystal at absolute zero =  zero     
    • 0Kelvins is the lowest , not actually achievable -273celsius
    • 4. Zeroth law of thermodynamics     
    • Zeroth law fundamental to, and assumed by, the other laws of thermodynamics    
    • if two bodies are each in thermal equilibrium with a third body -> then all three bodies are in thermal equilibrium with each other.
  19. Chemical properties of matter
    • properties which describe how substance will react or undergo chemical changes.
    • can vary greatly from one substance to another.
  20. chemical change
    • results in the formation of a new substance (or substances) with different physical and chemical properties than the initial substance (or substances)= chemical reaction.    
    • Most chemical reactions take place when particles of reactants collide with enough force to react.
    •  Bonds between atoms are broken and new bonds form between different atoms. 
    • breaking and forming takes place when particles of the original materials collide with one another.
  21. exothermic/endothermic representation w/ q
    • endothermic: Q on product side
    • exothermic: Q on reactant side
  22. possible changes during reaction
    • Physical -change of state
    • Chemical
    • nuclear - a change within the nucleus (protons or neutrons) 
  23. Radioactivity
    spontaneous disintegration of atomic nuclei accompanied by the emission of particles and/or penetrating rays. 
  24. alpha, beta, gamma
    • alpha: Helium nucleus, 4/2He
    • beta: 0/-1e
    • gamma: High-energy radiation, this is not a particle but a ray (or electromagnetic radiation)
  25. mass and atomic number notation:
    • bigger number on top! 
    • can also be called uranium 235, or U-235, if U-236 = isotope, more neutrons
  26. Nuclear reactions
    • transmutations of the elements themselves
    • make sure sub/super scripts are equal for conservation o charge
  27. Nuclear fission
    • process where heavy nucleus is split into two smaller nuclei      
    • Neutrons and large amounts of energy are released. 
  28. Nuclear fusion
    • process by which light nuclei join to form larger nuclei, releasing tremendous amounts of energy.
    • powers the massive energy output of the sun as it converts hydrogen and helium to other heavier elements.