Specific Heat
AIT Physics 1 Honors
Laboratory: Specific Heat and Conservation of Energy
When energy in the form of heat Q is added to a material, the temperature of the material rises. Note that temperature, in units of degrees Celsius (°C) or Kelvin (K), is a measure of how hot or cold a substance is, while heat, in units of joules (J) or calories (cal), is a measure of its thermal energy. 1cal = 4.19J.
A measure of the efficiency with which a substance can store this heat energy is known as specific heat capacity, or simply the specific heat, . The greater the material's specific heat, the more energy must be added to change its temperature. As an example, the specific heat of water is given as C
4186
J
,
Kg C
which means that 4186 Joules of heat are necessary to raise one kilogram of water one degree Celcius or
Kelvin. Other common specific heat values for various other materials are listed in CJ6 Chapter 12.
The heat necessary to cause a temperature change in a material (not a phase change) is Q
mC T
where C is the specific heat capacity of that material. Normally the change in temperature of the substance is the difference between its final and initial temperatures T T f Ti
When two bodies having different temperatures come into contact with each other, heat energy is transferred between the bodies. Take, for example, placing a piece of hot metal into a container of cool water. From experience we know over time that the metal sample will become cooler, while the water and its container will become warmer, until an equilibrium temperature is reached. Put another way, according to the law of energy conservation the total heat energy lost by the metal is the total heat energy gained by the water and container:
Qlost
Qmetal
Qgained
Qwater Qcontainer
mmCm Tm
mwCw Tw mcCc Tc
In thermodynamics (which we will start in a week) a negative sign would be used on the Qmetal term to maintain our sign convention for heat; we set the hot side to be negative because energy is
Laboratory: Specific Heat and Conservation of Energy
When energy in the form of heat Q is added to a material, the temperature of the material rises. Note that temperature, in units of degrees Celsius (°C) or Kelvin (K), is a measure of how hot or cold a substance is, while heat, in units of joules (J) or calories (cal), is a measure of its thermal energy. 1cal = 4.19J.
A measure of the efficiency with which a substance can store this heat energy is known as specific heat capacity, or simply the specific heat, . The greater the material's specific heat, the more energy must be added to change its temperature. As an example, the specific heat of water is given as C
4186
J
,
Kg C
which means that 4186 Joules of heat are necessary to raise one kilogram of water one degree Celcius or
Kelvin. Other common specific heat values for various other materials are listed in CJ6 Chapter 12.
The heat necessary to cause a temperature change in a material (not a phase change) is Q
mC T
where C is the specific heat capacity of that material. Normally the change in temperature of the substance is the difference between its final and initial temperatures T T f Ti
When two bodies having different temperatures come into contact with each other, heat energy is transferred between the bodies. Take, for example, placing a piece of hot metal into a container of cool water. From experience we know over time that the metal sample will become cooler, while the water and its container will become warmer, until an equilibrium temperature is reached. Put another way, according to the law of energy conservation the total heat energy lost by the metal is the total heat energy gained by the water and container:
Qlost
Qmetal
Qgained
Qwater Qcontainer
mmCm Tm
mwCw Tw mcCc Tc
In thermodynamics (which we will start in a week) a negative sign would be used on the Qmetal term to maintain our sign convention for heat; we set the hot side to be negative because energy is