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Unit 2 |
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Temperature and the Effects of Heat |
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Temperature |
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measure of ‘hotness’ or ‘coldness’ |
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measure of the average kinetic energy of the
molecules in a substance |
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Fahrenheit, Celsius, Kelvin, Rankine |
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Absolute temperature |
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true zero |
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Temperature conversions |
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F = 1.8
C + 32 |
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C = (F -
32) / 1.8 |
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K = C +
273 |
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R = F +
460 |
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Heat |
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energy transfer usually due to a temperature
difference |
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energy transfer may also be the result of a
chemical, nuclear, electrical or mechanical change |
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Btu, calorie, kilocalorie |
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Gas laws *** for all gas laws pressure and
temperature must be absolute |
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General gas law |
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Boyle’s law |
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Charles’ law |
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Gay-Lusaac’s law |
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Absolute pressure = gauge pressure + atmospheric
pressure |
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Atmospheric pressure can be measured using a
barometer. |
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Standard atmospheric pressure can be expressed
with many different units. |
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14.7 psi 760 mm of Hg
101.3 kPa 1 atmosphere
30 in. of Hg |
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Absolute temperature |
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the temperature at which the volume of a gas
becomes zero under constant pressure |
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Kelvin scale Rankine scale |
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- the volume is inversely proportional to the
absolute pressure of a gas at constant temperature
***
for all gas laws pressure and temperature must be absolute |
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- the volume is directly proportional to the
absolute temperature of a gas at constant pressure
***
for all gas laws pressure and temperature must be absolute |
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- the absolute pressure of a gas is directly
proportional to the absolute temperature for a constant volume
***
for all gas laws pressure and temperature must be absolute |
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Linear expansion (length, width, height,
thickness, etc.) |
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coefficient of linear expansion - a property of
the material; the relative change in one dimension per degree of
temperature change |
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Area expansion |
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Volume expansion |
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Specific Heat Capacity |
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amount of heat required to change the
temperature of a unit mass one degree.
(cal/g C, kcal/kg C or Btu/lb F ) |
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because of the definitions for cal and Btu, the
same values may be used for either English or metric |
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Phase changes |
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solid to liquid
(fusion) |
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liquid to gas
(vaporization) |
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conduction - heat transfer from higher temp. to
lower temp. due to molecular interaction |
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convection - heat transfer by mass transfer |
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radiation - heat transfer by waves |
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Heat of Combustion |
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heat produced per unit of mass of the substance
when it is burned in oxygen |
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1st law of thermodynamics |
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conservation of energy (heat, work, internal
energy) |
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2nd law of thermodynamics |
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heat will NOT flow spontaneously from a colder
body to a warmer body |
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100% efficiency is not possible |
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3rd law of thermodynamics |
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absolute zero is not obtainable |
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thermal energy |
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thermal equilibrium |
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sublimation |
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evaporation |
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Notes