Class Notes 10/8

Thermodynamics

-study of how large numbers of particles interact with their surroundings during energy transfer

What are systems?

-collection of entities (people places things) with

   --a boundary

   --an environment

   --input/output

   --feedback

Heat and Temperature

Heat: transfer of energy across the boundary of a system due to a temperature difference between the system and its surroundings. 

Temperature: average thermal energy of particles

Scales: Kelvin, celsius, fahrenheit

Heat capacity:  C=Q/change in temperature

specific heat: c=Q/(mxchange in T)

Q=c m change in T (depends on mass and c)

First Law of Thermodynamics

1. Energy is conserved in a closed system

2. Heat is energy

Heat is not conserved; work energy is not conserved. Total internal energy is conserved.

E(internal)=Heat+work

internal energy: kinetic energy of molecules, 

*Friction causes heat!

heat is work, work is heat

Heat Energy Transfer-Conduction

transfer of heat-exchange of average kinetic energy of atoms, molecules, and electrons.

Convection:energy transferred by the movement of a heated substance

natural convection; due to differences in density

-heated air expands, lowering the density

-pushed up by higher density air

ex; boil water

-forced convection:heated fluid moves due to fan or pump

Radiation: all objects radiate energy as electromagnetic waves

-produced by thermal vibrations of molecules