1. Chapter 16 Thermal Energy and Heat
Physical Science

4. Thermal Energy and Matter 16.1
In 1700s, scientist thought heat was fluid called caloric
Not fluid or state of matter but related to motion
Work and Heat
Heat – transfer of thermal E from one object to another bc of temp difference
Flow from hot to cold
Can occur bc of friction from work
Temperature
Measure of how hot or cold bc of movement of particle
average kinetic E of the particles in an object due to random motion
all particle collisions transfer thermal E

5. The particles inside an ice cube are moving very slowly.
The particles in boiling water are moving very fast.

6. Thermal Energy 16.1 Total potential and kinetic E of all the particles
Depends on:
Mass
Cup of hot tea vs. teaspoon of hot tea
Same temp = so same average kinetic energy
Cup tea more thermal E b/c more particles
Temperature
Cup of hot tea vs. cup of cold tea
Same mass, same # of particles
Different average kinetic E = energy of particle higher in hot tea = greater thermal E
Phase (solid, liquid, gas)
Phase changes transfer thermal energy

7. Thermal Contraction and Expansion 16.1
Thermal Expansion – increase in volume of material bc of temp increase  particles move faster  collide more often  expand
Gases expand more than liquids, liquids more than solids
bc force of attraction is less
Thermal Contraction
Temperature decreases  particles move more slowly  collide less often

8. Specific Heat 16.1
Amount of heat needed to raise the temperature of 1 gram of a material by 1 degree
Lower specific heat = heat faster
Joules per gram per degree Celsius
Q = m(c)(ΔT)

9. Measuring Heat Change 16.1
Calorimeter – instrument used to measure changes in thermal E
Used to measure specific heat of Al 

10. Math Practice # 1- 5 Page 477

13. Heat and Thermodynamics 16.2
Conduction – transfer of thermal E
Not transfer of matter
Materials are TOUCHING
Slower in gases than liquids, liquids slower than solids
bc of particle location
Faster in metals bc electrons free to move (sea of e-)
Thermal Conductors – material that conducts well
Metal
Does not have to be hot  tile floor colder than wooden floor bc tile is a better conductor and transfers thermal E quickly to skin
Thermal Insulator – material that conducts poorly
Wood, air, plastic, foam

14. Convection 16.2
Transfer of thermal energy when particles of a fluid (liquid or gas) move from place to place
Hot to cold
Convection current- fluid circulate in a loop as it alternately heats up and cools down
Occurs in oceans, weather, and movement of hot rock in Earth’s interior
Ovens

15. Radiation 16.2 Transfer of E by waves moving thru space
All objects radiate energy
As temp increases, radiation increases

17. Thermodynamics 16.2
The study of conversions between thermal energy and other forms of energy
1st Law – energy is neither created or destroyed
2nd Law – thermal E can flow from colder to hotter objects only when work is done
Relates to entropy (disorganization of system)
Heat engines –converts heat into work
Efficiency is always less than 100%
Waste heat = thermal E not converted to work
Spontaneous changes – makes system less orderly unless work is done
World is always becoming less orderly
3rd Law – absolute zero (O K) cannot be reached

18. Solar Homes
3 clips = 4 minutes

20. Heat Engines 16.3
External Combustion Engine – an engine that burns fuel outside the engine
1st used to pump water out of coal mines
Hot steam enters in right  valve slide to left  steam trapped  expands and pushes piston  heat converted to work

21. An External Combustion Engine
Figure 11
An External Combustion Engine

22. An External Combustion Engine
Figure 11
An External Combustion Engine

23. An External Combustion Engine
Figure 11
An External Combustion Engine

24. Heat Engines 16.3
Internal Combustion Engines – Fuel burns inside the engine
Most use pistons that move in a cylinder
Each motion up and down = stroke
Linear motion is converted to rotary motion by crankshaft
Crankshaft = connected to transmission (linked to wheels and driveshaft
6 min

25. An Internal Combustion Engine
Figure 12
An Internal Combustion Engine

26. Heating System 16.3
Central heating system – heats many rooms from 1 central location
Commonly used electrical energy, natural gas, oil, and coal
Differ in how they transfer thermal energy
Hot-Water Heat
Circulating pump carries hot water to radiators in each room  conduction (water to radiator)  conduction and radiation (heating room) convection in room
Steam Heating
Similar to hot water heat but use steam instead
Often used in older buildings
Electric Baseboard Heating
Use electric energy (convert electrical to thermal)
Hot coils heat air by conduction and radiations  convection causes circulation
Space heaters are similar
Forced-Air Heating
Use fans to circulate air thru ducts to rooms  convection circulates air in room
b/c warm air rises, warm-air vents are located in floor
Advantage = air is cleaned as pass thru filters

28. Cooling Systems 16.3
Heat pump – device that reverses the normal flow of thermal heat
Refrigerant – fluid that vaporizes and condenses inside the tubing of a heat pump
Absorbs heat  vaporizes  turns into gas
Gives off heat  condenses  turns into liquid
Heat pump must do work to refrigerant to reverse flow
Refrigerators- heap pump that transfers thermal E from cold food compartment to warm room
Open door adds more heat to room than it removes b/c coils get hotter
Air Conditioner
Must do work

30.
2 minutes