Unit 07 Vocabulary

1. Temperature -- a measure of the average translational kinetic energy per particle in a substance.
2. Celsius scale -- a temperature scale that sets zero degrees at the freezing point of pure water and one hundred degrees at its boiling point.
3. Kelvin scale -- a temperature scale that uses the Celsius scale, but shifts the zero point to absolute zero (or -273.16 degrees Celsius.)
4. Absolute zero -- the lowest possible temperature that a substance my have -- the temperature at which molecules of the substance have their minimum kinetic energy.
5. Heat -- the energy that flows from a substance of a higher temperature to a substance of lower temperature, measured in Joules or sometimes calories.
6. Internal energy -- the total of all molecular energies (kinetic plus potential) that are internal to a substance.
7. Conduction -- the transfer of heat energy by molecular and electron collisions within a substance (especially a solid.)
8. Convection -- the transfer of heat energy in a fluid (gas or liquid) by means of currents in the heated fluid. As a result of the uneven heating, parts of the fluid move, carrying heat energy with it.
9. Radiation -- the transfer of energy by means of electromagnetic waves.
10. Newton's law of cooling -- the rate of loss of heat energy from a warm object is proportional to the temperature difference between the object and its surroundings.
11. Greenhouse effect -- warming of the lower atmosphere by short-wavelength radiation from the Sun that penetrates the atmosphere, is absorbed by the Earth and is re-radiated at longer wavelengths that cannot easily escape the Earth's atmosphere.
12. Thermodynamics -- the study of heat and its transformation into different forms of energy.
13. First law of thermodynamics -- a restatement of the law of conservation of energy, applied to systems in which energy is transferred by heat and/or work. The heat added to a system equals its increase in internal energy plus the external work it does on the environment.
14. Adiabatic process -- a process, often fast expansion or compression, in which no heat enters or leaves the system.
15. Second law of thermodynamics -- thermal energy never spontaneously flows from a cold object to a hot object. Also, no machine can be completely efficient in converting heat to work; some of the heat supplied to the machine at high temperature is dissipated as waste heat at lower temperature. And, finally, all systems tend to become more and more disordered as time goes by.
16. Heat engine -- a device that uses heat as input and provides work as output.
17. Entropy -- a measure of the disorder of a system. Whenever energy freely transforms from one form into another, the direction of transformation is toward a state of greater disorder and therefore one of greater entropy.

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