Chapter 12.1 Temperature and Thermal Energy
What makes a hot body hot?
In the 18th century scientists came up with the caloric theory of heat In this theory an invisible substance called “caloric” created heat. Only in the mid-nineteenth century did scientists develop the kinetic-molecular theory. This stated that as the particles moved faster they created a greater kinetic energy and thus heat.
Thermal Energy and Temperature
According to the kinetic-molecular theory hot bodies have a greater average thermal energy than a cold body. Temperature is measured on a definite scale. Thermal energy is proportional to the number of particles in the object, while temperature is not.
Equilibrium and Thermometry
Temperature is measured using a process called conduction. When your body and the thermometer are at the same temperature they are at thermal equilibrium. Thermometers contain a liquid that will expand when heated and retract when cooled, thus the liquid rises and falls.
Temperature Scales: Celsius and Kelvin
Each interval on the kelvin scale is called a kelvin. A reading of 0 o C is where water freezes. However, a reading of 0K is absolute zero. At absolute zero all molecules cease to move. We have never been able to create conditions of absolute zero.
Heat and Thermal Energy
Heat is the energy that flows between two objects due to a temperature difference. The transfer of energy through electro- magnetic waves is radiation. The motion of fluid due to a temperature difference is called convection. The specific heat of a material is the amount of energy needed to change its temperature
Specific Heat of Common Substances Material Specific heat Material Specific heat J/kg x K J/kg x K aluminum 903 lead 130 brass 376 methanol 2450 carbon 710 silver 235 copper 385 steam 2020 glass 664 water 4180 ice 2060 zinc 388 iron 450
Heat Transfer Q=mC T = mC(T final – T initial ) T= temperature (K) m= mass (Kg) Q= heat gained or lost (J) C=specific heat (J/Kg*K) heat transfer. Chart. Heart Transfer. N.p., n.d. Web. 11 Jan