Heat and Temperature
Temperature
The measure of the average kinetic energy of all of the particles within an object.
Temperature and Energy
All particles are moving and have kinetic energy.
We can not measure the KE of each molecule, so we take an average of each one.
Taking temperature is finding the average KE of molecules.
Feeling hot or cold is a rough estimate.It is subjective.
Thermometer
A device that measures temperature
Most thermometers rely on the expansion of either fluids or metal to work.
Electric thermometers rely on a change in current.
Temperature Scales
Image/Text/Data from the University of Illinois WW2010 Project
Celsius-Fahrenheit
Celsius – Fahrenheit Conversion Equation
Fahrenheit temperature = (9/5 X Celsius temperature) +
32.0
TF = 9/5t + 32.0
Fahrenheit-Celsius
Fahrenheit – Celsius Conversion Equation
Celsius temperature = 5/9 (Fahrenheit temperature –
32.0)
T = 5/9(TF – 32.0)
Kelvin Based on Absolute
Zero (theoretical)The temperature at
which an object’s energy is minimal
Celsius – Kelvin Conversion EquationKelvin temperature =
Celsius temperature + 273T = t + 273
Relating Temperature to Energy Transfer as Heat
You feel hot and cold because of transfer of energy. Molecules must come into contact with one another.
Hot = absorbing energy from objectCold = releasing energy from object
Heat
The transfer of energy from the particles of one object to those of another object due to a temperature difference between the two objects
Thermal Energy
Actions that Increase
Thermal Energy
Explanation
Raise the temperature of the object
Thermal Energy
Actions that Increase
Thermal Energy
Explanation
Raise the temperature of the object
Increases the kinetic energy of the atoms or molecules
Thermal Energy
Actions that Increase
Thermal Energy
Explanation
Raise the temperature of the object
Increases the kinetic energy of the atoms or molecules
Pull atoms or molecules that attract one another farther apart
Thermal Energy
Actions that Increase
Thermal Energy
Explanation
Raise the temperature of the object
Increases the kinetic energy of the atoms or molecules
Pull atoms or molecules that attract one another farther apart
Increases the potential energy of the atoms or molecules
Thermal Energy
Actions that Increase
Thermal Energy
Explanation
Raise the temperature of the object
Increases the kinetic energy of the atoms or molecules
Pull atoms or molecules that attract one another farther apart
Increases the potential energy of the atoms or molecules
Add mass to the object, without changing its temperature
Thermal Energy
Actions that Increase
Thermal Energy
Explanation
Raise the temperature of the object
Increases the kinetic energy of the atoms or molecules
Pull atoms or molecules that attract one another farther apart
Increases the potential energy of the atoms or molecules
Add mass to the object, without changing its temperature
More molecules at the same level of energy means more total energy in the object.
Thermal Energy Equation
Q = m ΔT CQ = change in thermal energy (J)
m = mass (kg)ΔT = change in temperature (˚C)
C = specific heat (J/kg ˚C)
Problem Plug and Chug
Q = 0.5 kg • 60 ˚C • 800 J/kg ˚C mass x change of temp x
specific heat
Q = 24,000 J
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