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Temperature and Heat Heat – the energy transferred between objects because of a temperature difference.
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Temperature and Heat
Heat – the energy transferred between objects because of a temperature difference.
Temperature and Heat
Thermal contact – two objects are in thermal contact if heat can flow between them.
Temperature and Heat
Thermal equilibrium – if two objects are in thermal contact, but no heat flows between them, they are said to be in thermal equilibrium. (They must be at the same temperature).
Temperature and Heat
Thermodynamics – the study of physical processes involving the transfer of heat.
Temperature and Heat
Temperature – the quantity that determines whether two objects are in thermal equilibrium. The temperature of a system depends on the average kinetic energy of the particles making up the system.
Temperature and Heat
Celsius temperature scale-
Freezing point of H2O = 0 oC
Boiling point of H2O = 100 oC
Temperature and Heat
Celsius temperature scale-Notation- a temperature of five degrees celsius is written 5 oC
Temperature and Heat
Celsius temperature scale-Notation- a temperature change of five degrees celsius is written 5 Co
Temperature and Heat
Celsius temperature scale-
There are 100 divisions between the zero and 100 point
Temperature and Heat
Fahrenheit temperature scale-
Freezing point of H2O = 32 oF
Boiling point of H2O = 212 oF
Temperature and Heat
Fahrenheit temperature scale-
There are 180 divisions between the 32 and 212 point.
Temperature and Heat
Kelvin temperature scale-
Freezing point of H2O=273.15 K
Boiling point of H2O=373.15 K
Temperature and Heat
Kelvin temperature scale- an absolute scale with no negative equilibrium temperatures.
0 K = absolute zero
Temperature and Heat
Conversions –
9T T 32
5F C
Temperature and Heat
Conversions –
5T T 32
9C F
Figure 16-8The Mechanical Equivalent of Heat
Temperature and Heat
James Prescott Joule demonstrated that mechanical work can be converted to heat, and that energy is conserved in the process. 1cal=4.186J
Temperature and HeatThermal expansion – when the temperature of most materials increases, they expand. When a substance is heated, its particles begin moving more and thus usually maintain a greater average separation.
Temperature and HeatLinear expansion –
the change in the length of a material
the coefficient of linear thermal expansion of the material
the original length of the material
the temperature change of the material
o
o
L L T
where
L
L
T
Temperature and HeatArea expansion –
2
the change in the area of a material
the coefficient of linear thermal expansion of the material
the original area of the material
the temperature change of the material
o
o
A A T
where
A
A
T
Temperature and HeatVolume expansion –
3
the change in the volume of a material
the coefficient of linear thermal expansion of the material
the original volume of the material
the temperature change of the material
o
o
V V T
where
v
V
T
Temperature and HeatVolume expansion –
When working with liquids we use the coefficient of volume expansion.
Temperature and HeatLinear expansion –
the change in the volume of a material
the coefficient of volume thermal expansion of the material
the original volume of the material
the temperature change of the material
o
o
V V T
where
V
V
T
Temperature and HeatHeat flow–
Conduction – heat flow without bulk motion of matter. The result of atoms interacting with their neighbors.
Temperature and HeatHeat flow– Conduction
thermal conductivity of the material
heat exchanged
cross-sectional area of the material
the temperature difference between the two sides of the material
length of the m
TQ kA t
L
where
k
Q
A
T
L
aterial
the time interval during which the exchange took placet
Figure 16-9Heat Conduction Through a Rod
Temperature and HeatHeat flow–
Convection – heat exchange due to the bulk motion of an unevenly heated fluid.
Figure 16-11Alternating
Land and Sea Breezes
Temperature and HeatHeat flow–
Radiation – heat exchange due to electromagnetic radiation such as sunlight, infrared light, and microwaves. Does not require matter to transfer heat.
