heat & temperature
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Heat & Temperature. Concept Summary Batesville High School Physics. Historical Heat. As late as 200 years ago, heat was regarded as a fluid, called “ caloric ”. It was believed that this caloric fluid flows from hot objects to cold objects. Historical Heat. - PowerPoint PPT PresentationTRANSCRIPT
Concept Summary
Batesville High School Physics
Historical Heat As late as 200 years ago, heat was
regarded as a fluid, called “caloric”. It was believed that this caloric fluid
flows from hot objects to cold objects.
Historical HeatThe scientific study of heat was
motivated by the Industrial Revolution with its use of steam engines and machines.
In the 19th century, James Prescott Joule (and others) showed that heat is a form of energy.
Heat TermsActually, thermal energy is only called
heat when it is moving between objects.
Heat transfers thermal energy from one object to another (like work).
Energy inside an object is properly called internal energy - the kinetic and potential energy of its particles.
Adding HeatSo, when heat energy is transferred to
an object, the energy “shows up” as kinetic energy & potential energy of the object’s particles (atoms, molecules, etc.)
TemperatureAn object’s temperature is related to
the average kinetic energy of the particles in an object.
Higher average KE means higher temperature.
Moving Heat EnergyHeat energy “flows” from an object at
higher temperature to an object at lower temperature - if the objects are in thermal contact.
(To make energy move the other way, you have to do work.)
Thermal EquilibriumHeat energy will “flow” until the two
objects reach the same temperature - they are then in thermal equilibrium.
The Lowest TemperatureSince there is a minimum kinetic energy
for particles (0 J), there is a lowest possible temperature – absolute zero.
Scientists have produced temperatures within a small fraction of a degree of absolute zero.
Temperature Units
Name Water freezes
Room Temp.
Water boils
Absolute Zero
Fahrenheit 32o 70o 212o -459.7o
Celsius 0o 21o 100o -273.15o
Kelvin 273.1 294 373.1 0
Temperature is NOT HeatAn object may have a relatively high
temperature and a relatively low internal energy.
An object may have a relatively low temperature and a relatively high internal energy.
Temperature is NOT Heat It is possible for heat to flow from an
object with very little energy (but high temperature) to an object with lots of energy (but low temperature).
Temperature and HeatWhen you add heat energy to an
object, its temperature may (or may not!) increase.
Measuring Heat EnergySince heat is energy, it can be
measured in Joules.A common (and old-fashioned) unit of
heat energy is the calorie.
The calorie & the Calorie1 calorie is the amount of heat needed
to raise the temperature of water by 1oC.
1 Calorie = 1 kilocalorie = 1000 caloriesThe Calorie is the “diet calorie”.
Specific Heat Capacity1 calorie of heat will raise the
temperature of different substances by different amounts.
The amount of heat energy required to raise the temperature of a substance by 1oC is called the specific heat capacity, or specific heat.
Specific Heat of WaterBy definition, the specific heat of water
is 1.This is a high specific heat, meaning it
takes a relatively large amount of energy to raise the temperature of water – water holds a lot of energy.
Calculating Heat EnergyThe amount of heat energy needed to
raise the temperature of a a substance depends on: The amount of the substance The specific heat of the substance The change in temperature
Calculating Heat EnergyH = mcT
where: H = heat energy added/removed m = mass c = specific heat T = change in temperature
Moving Heat EnergySince heat is energy, heat can be
conserved in an isolated system. In a 2-object system:Heat lost by object A = heat gained by
object BmAcATA = mBCBTB
The End