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24 Cards in this Set
- Front
- Back
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Absolute Zero |
lowest temp on "absolute scale" (no negatives)
occurs when average molecular motion is zero
lowest degree possible (0K) |
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Specific Heat (c) |
amount of heat energy needed to raise the temp of 1g of a substance by 1 degree celsius
amount of heat energy lost by 1g of a substance as it cools by 1 degree celsius |
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Calorie (cal): |
the quantitive measure of heat exchange
use formula to calculate heat gained/lost by a substance:
(Q) = m x c x change in T |
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Six Phase Changes:
LS,SL,LG,GL,SG,GS, |
LS (solidification), SL (fusion), LG (vaporization), GL (condensation), SG (sublimation), GS (deposition)
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Latent Heat
Lf - Latent Fusion (79.7 cal/g)
Lv - Latent Vaporization (538.7 cal/g) |
stored internal potential energy required to bring about phase change for a mass
during fusion and vaporization energy is needed to overcome attraction between molecules and spread them apart
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Conduction "to lead together"
*method of heat transfer |
energy is moved from one vibrating molecule to another by bumping/colliding into each other
energy transferred for 1 particle to another directly |
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Convection "to carry together"
*method of heat transfer |
heat energy is transferred in a substance by molecules which are free to move and carry their energy with them
density differences cause convection |
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Radiation (thermal)
*method of heat transfer |
electromagnetic energy (waves) are transferred through empty space , gases, liquids, and solids. |
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Entropy (S) "a change in" |
every isolated system becomes more disordered with time
a system naturally moves from a more orderly state toward a more disorderly state |
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Kinetic Molecular Theory |
all matter is composed of tiny atoms in constant random motion, their average KE determine the temp of the substance |
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Thermal Equilibrium |
"equilibrium" implies a state of balance
Heat energy will flow from higher KE to lower KE to establish thermal equilibrium |
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"Sources and Sinks" |
heat energy always flows from higher average KE to lower average KE in attempt to establish thermal equilibrium |
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Thermal Expansion |
G >> L > S * all phases expand when given heat energy
spaces between molecules increase not the size of the molecules "elbow room" |
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Thermometry "heat measure" |
temp can't be directly measured bc volumes of irregular shaped rooms
measured in terms of expansion
temp indicated average KE in a substance |
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Differences between heat & temp |
( T ) measure of average KE that molecules in a substance have "agitation"
( Q ) measures how much KE a substance has
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Evaporative Cooling |
evaporation is a cooling process (sweating, pigs and dogs)
function of "relative humidity" |
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Three methods of transferring Heat Energy |
conduction
convection
radiation |
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Thermal Conductivity ( k ) |
how effective a substance can conduct heat
molecules close are good conductors
molecules farther apart are bad conductor |
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Rate of Heat Conduction ( H ) |
( H ) = (change in Q / change in T)
= k A (change in T) / L
k-thermal conductivity A-cross sectional area L-length of substance (thickness)
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Five methods of Producing Heat |
mechanical
electric current
Chemical Rx's
Radiant
Atomic Rx's |
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Method of Mixtures
calorimeter -> Heat of Combustion ( Hc ) |
( Hc ) heat produced per unit mass
weight of fuel when burned in the presence of an appropriate amount of oxygen |
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R-Value (R) |
thermal resistance property of a material (thermal insulation)
( R ) = p L = L / k -> R = L k
notes use inches and btu p-thermal resistivity k-thermal conductivity L-length of substance (thickness) |
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Thermodynamic Laws |
Zeroth Law : heat flows from higher average KE to lower average KE until thermal equilibrium is reached ** same average KE, already in Therm. Equ.
First Law: Energy gained by a system = to energy lost by its surroundings **isolated system total energy is constant
Second Law: 1st law doesn't place restriction on direction of thermodynamic process
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Brownian Motion |
random motion of particle suspended fluid (liquid or gas) resulting from their collision w/ the molecules in the gas or liquid
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