1. Theories of Heat

2. all substances contain tiny, constantly moving particles Kinetic Theory

3. the sum of the kinetic energy of the random motion of the particles average kinetic energy of particles is proportional to the temperature Thermal Energy

4. matter can be subdivided diffusion: the spreading of a substance through particle motion alone much faster in gases than liquids Diffusion

5. gas molecules move faster than liquid molecules easily demonstrated with substances like ammonia and bromine vapor Diffusion

6. affects microscopic particles caused by random, asymmetrical collisions of liquid or gas molecules against the particles Brownian Motion

7. claimed heat is a material fluid (caloric) that flows from hot bodies to cold bodies evidence for the kinetic theory eventually destroyed this idea Caloric Theory

8. studied conversion of mechanical energy to thermal energy mechanical equivalent of heat Joule’s Research

9. various experiments gave slightly different results currently accepted value of the mechanical equivalent of thermal energy: Joule’s Research 4.186 N·m = 1 cal (at 15°C)

10. Joule’s Research In his honor, the N·m was renamed the “joule,” the SI derived unit of energy, work, and heat.

11. Thermal Energy and Matter

12. Heat Capacity It is not always the hottest object that has the greatest amount of thermal energy! Heat Capacity (C): amount of thermal energy required to raise the temperature of entire object 1°C.

13. Heat Capacity Heat (Q): amount of thermal energy added to or taken from a system SI unit: J/°C C = ΔtΔt Q object

14. Heat Capacity Δt = change in temperature technically incorrect to say that a system has a certain amount of heat C = ΔtΔt Q object

15. Specific Heat analogous to the specific density of a material specific heat capacity = heat capacity per gram

16. Specific Heat specific heat (c sp ) of a substance is the amount of thermal energy required to raise the temperature of 1 g of the substance by 1°C SI units: J/g·°C

17. Specific Heat specific heat of water: 1 cal/g·°C (at 15°C) 4.18 J/g·°C (near room temperature)

18. Specific Heat to calculate specific heat: c sp = mΔtmΔt Q and by definition: C = m(c sp )

19. Conservation when an object gains heat, its surroundings lose that same amount of heat heat-balance equations: Q system = -Q surroundings Q system + Q surroundings = 0 J

20. Conservation adiabatic vessel: one that allows no heat to enter or leave its contents calorimeter: container designed to minimize the exchange of thermal energy with its surroundings

21. Conservation In computational work, it must be remembered to include the calorimeter’s gain or loss of heat.

22. Heat and Phase Transitions an amount of heat is required to melt a solid or to vaporize a liquid adding this heat will not change the temperature while melting or vaporizing occurs

23. Heat and Phase Transitions latent heat of fusion (L f ): amount of thermal energy required to melt 1 kg of the substance at its melting point L f = m Q melt

24. Heat and Phase Transitions latent heat of vaporization (L v ): amount of thermal energy required to vaporize 1 kg of the substance at its boiling point L v = m Q boil

25. Heat and Phase Transitions Example 15-6: Why are there five parts to this?

26. Mechanisms for Heat Transfer

27. Conduction the flow of thermal energy from one object to another through contact conductors: materials that conduct thermal energy easily

28. Conduction conductors are more likely to have free electrons insulators: materials that do not conduct thermal energy easily

29. Convection the transfer of thermal energy from one place to another by the physical translation of particles between locations

30. Convection most liquids and gases rise when heated water has unusual properties

31. Radiation travels without the use of an intervening medium converted to thermal energy when absorbed by matter all objects radiate thermal energy

32. Radiation Stefan’s law gives the correspondence between absolute temperature (T) and the power of its radiant energy (S): S = σT 4

33. Radiation Stefan-Boltzmann constant: σ = 5.67 × 10 -8 W/(m 2 ·K 4 ) S is proportional to temperature to the fourth power S = σT 4

34. Radiation black objects absorb and radiate radiant energy better than other objects blackbody: a perfect (ideal) radiator and absorber