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13 Cards in this Set
- Front
- Back
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Zeroth Law Thermodynamics
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If Equ of A= B and equ. B= C then A=C *thermal equilibrium -no net heat will flow between the objects - does not imply physical contact |
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Temperature - from zeroth law |
Key: Temp is a phys. property of matter - related to average kinetic energy of particles differences in temp. determine the direction of heat transfer - so Heat is flows between object not in thermal equilibrium measured by temperature - Fahrenheit (F): 32 and 212 FP and BP Water - Celsius (C): 0 and 100 freezing and BP water - Kelvin (K): for scientific measures * degrees Celsius - 273 ex: 0 degrees C = -273K defines absolute zero (for 3rd law thermo) |
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Third Law of Thermodynamics
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entropy of a perfect crystal- @ absolute zero - at 0K or -273C, -460F - no thermal energy F= 9/5 C + 32 K= C + 273 |
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Functions of temperature - what Δ because of ΔT - |
1. Length 2. Volume 3. Solubility 4. conductivity of matter Most Solids - ΔL b/c of ΔT Change of length of solid will Δ Inc^ T = Inc^ L vise versa ΔL=aLΔT a= coeff. linear expansion Liquids - ΔV change in volume ΔV= bVΔT *b=coeff. volumetrix expansion |
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Systems - isolated -closed -open |
System: portion under analysis surroundings-rest of universe Isolated: no ΔE or Δmatter w/ surroundings * RARE Closed : can ΔE, but not matter *gases w/ pistons , most common Open system: can Δmatter and ΔE w/ surroundings |
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State Functions
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thermodynamic properties of only the current equilibrium state of a system - defined by being independent of path taken to get to equilibrium
Pressure P Density p Temperature T Volume V enthalpy H Internnal E (U) Gibbs G Entropy S |
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First Law Thermodynamics
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Δ total energy system equal to amount of energy transferred in the form of heat to the system - minus the amount of energy transferred from the system in the form of work ΔU = Q - W Internal energy = transfer energy - work
Δ Internal Energy (+) Value (-) Value Heat (Q) Heat into sys. Heat Out sys Work (W) Work by sys Work on sys expansion Compress. |
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Heat- second law of thermodynamics
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Heat: objects in thermal contact -not in thermal equilibrium will exchange heat High T--> low T Heat Unit: Joules (J) - or calorie (cal) nutritional calorie (Cal) -1C= 1000c 1Cal= 1000cal= 4184 J=3.97 BTU |
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Types of Heat Tranfer
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Conduction -direct transfer between objects KE Δ from one object to another ex: hov stove conducts burn to your finger Convection - transfer heat by physical motion of fluid over a material only fluids and gases - use fans to circulate hot air inside oven -cook more rapidly - can use to cool objects- water over vial Radiation transfer heat via electromagnetic waves - can transfer via vacuum - electrical coils, gas flames to heat insulated metal box - heat radiates to open space and absorbs into food |
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Specific Heat |
*remember T is constant at phase changes Specific heat (c): amount of heat energy required to raise 1 gram matter 1 degree celsius or K units: 1 cal/ g K or as 4.184 J/ g K **know water specific heat = 1 cal/gK equation: q=mcΔT nmemonic:QMCAT! q= heat gained/lost by object |
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Heat transformation
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@phase change, any heat add/remo. will not result in a ΔT until full change in phase -adding heat= increase KE of molecules being heated equation for amount heat gain/lossed @ phase change q=mL L: heat of transformation or latent h Solid to Liquid - fusion/melting Liquid to Solid Freezing/solidification Liquid to gas boiling, evap., vaporization Gas to liquid condensation Solid to gas Sublimation |
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Thermodynamic Processes
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Isothermal - constant temperature Q= W Adiabatic - no heat exchange Q=0, so ΔU= -W Isobaric - constant pressure -only volume increases Isovolumetric -volume does not change W=0 so ΔU= Q on a P-V Graph Volume X and Pressure on Y Axis - Isobaric (ΔV only) will be constant line across - Isovolumetric (ΔP only) straight line, down, no slope |
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Entropy- Second law of thermodynamics
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objects in thermal contact, not at thermal Eq will not exchange heat energy (high to low) until both @ Eq - energy constantly being dispersed
- energy will spontaneously disperse from being localized to becoming spread out if not hindered - best example: liquid water and frozen ice Equation: ΔS = Qrev/ T Q= heat gained/lost units S: J/ mol K energy INTO a system: entropy increases energy out of a system: entropy decrease - at given temperatures **unidirectional: think of video of explosion - energy in a closed system will spontaneously spread out and entropy increases if not held back ΔS uni = ΔS sys + ΔSsurrounding > 0 entropy of universe always increasing (closed system - natural process and irreversible |
