1. HEAT ENGINES

2. HEAT ENGINE
A heat engine is any device that changes thermal energy into mechanical energy so work can be done.
Mechanical work can be done only if heat flows from a high-temperature to low- temperature region.

3. HEAT FLOW IN A
High Temp
Heat in
Work
Heat out
LowerTemp

4. HEAT ENGINE (STEAM)
THERMAL ENERGY IN : MECHANICAL ENERGY OUT

5. The process of an internal combustion engine resembles that of a heat engine.

6. HEAT ENGINES
Only some of the heat transferred from the high- temperature region can be transformed into mechanical energy (work). The remainder of the thermal energy is exhausted as waste heat.

7. Phases of Matter Solid Liquid Gas Definite volume and shape
Undefined shape
Plasma
Undefined volume and shape
Electrically charged gas—High temp!
Neon, lightning, stars, auroras, fluorescent bulbs
Gas
Undefined volume and shape

8. Melting and Evaporation Require Input of Thermal Energy
Melting (requires heat of fusion)
Heat of fusion is released when liquids freeze
Evaporation (requires heat of vaporization)
Heat of vaporization is released when gases condense

9. Evaporation vs. Condensation
Evaporation is a cooling process
Evaporation causes the temperature of the liquid to decrease (removes thermal energy from surroundings)
Condensation is a warming process
Condensation causes the temperature of the surroundings to increase (adds thermal energy to the surroundings)

10. 23.8 Energy and Changes of Phase
If you heat a solid sufficiently, it will melt and become a liquid.
If you heat the liquid, it will vaporize and become a gas.
The change in the internal energy of a substance causes the change of phase. 10

11. 23.1 Evaporation
The cloth covering on the sides of the canteen promotes cooling when it is wet. As the faster-moving water molecules leave the cloth, the temperature of the cloth decreases. 11

12. Starter Question #2 How does a thermometer work?
The kinetic theory be used to explain expansion and contraction of materials when the temperature of the material changes.
As the temperature rises, heat is transferred from the surroundings to the liquid inside the thermometer and the molecules that compose the liquid vibrate faster. This causes the liquid to expand and rise.
As the temperature falls, heat is transferred away from the liquid inside to the surroundings and the molecules that compose this liquid slow down. This causes the liquid to contract. 12

13. Air temperature = Liquid temperature
The liquid in the thermometer stops rising or falling when thermal equilibrium is reached (no more heat flow!)
Air temperature = Liquid temperature

14. Winter Vs. Summer Heat Flow
In winter
-Heat loss from inside (warmer) to outside (colder)
-Heating system must operate to transfer thermal energy from fuel to fluid to room to keep house warm
In summer
-Heat gain from outside (warmer) to inside (cooler)
- Cooling system must operate to transfer incoming heat entering the house back to the outside

15. 21.7 The High Specific Heat Capacity of Water
Water has a high specific heat and is transparent, so it takes more energy to heat up than land does. 15

16. Moderating Effect of Water on Climate
Water has a high specific heat capacity. This means…
It takes a large amount of heat to raise its temperature
It absorbs a large amount of heat
It stores a large amount of heat
It has to give up a large amount of heat in order to cool down
It takes a long time for water to cool down

17. Moderating Effect of Water on Climate
During the summer, surrounding air is cooled by the water and keeps the coast cooler than the intercontinental locations.
During the winter, the surrounding air is warmed by the water and keeps the coast warmer than the intercontinental locations.
SAN FRANCISCO, CA

18. Gulf Stream brings warm water northeast from the Caribbean.
21.7 The High Specific Heat Capacity of Water
Water stores and hold heat well because of its high specific heat. This affects global climate.
Gulf Stream brings warm water northeast from the Caribbean. 18

20. Thermal Front The Gulf Stream (warm water from equator) meets
The Labrador Current (cold water from polar region)
Labrador Current
Gulf Stream

21. 21.7 The High Specific Heat Capacity of Water
Climate of America
On the west coast, air moves from the Pacific Ocean to the land.
In winter, the water warms the air that moves over it and warms the western coastal regions of North America.
In summer, the water cools the air and the western coastal regions are cooled.
The central interior of a large continent usually experiences extremes of temperature.
Land, with a lower specific heat capacity, gets hot in summer but cools rapidly in winter. 21

22. Look at a world globe and notice the high latitude of Europe.
21.7 The High Specific Heat Capacity of Water
Climate of Europe
Look at a world globe and notice the high latitude of Europe.
Both Europe and Canada get about the same amount of the sun’s energy per square kilometer. 22

23. Marine Climate
Continental Climate
Cork
Edmonton

24. Marine Climate
Continental Climate
Cork
Edmonton
Same insolation angle, different climate due to proximity to water and the warming effect from the Gulf Stream

25. The Gulf Stream brings warm winters to Ireland and the prevailing winds off the Atlantic carry with them rain. It means grass can grow almost all year round — creating the lush sweeping pastures of the Emerald Isle. Today they make up 93 percent of all farmland. No other country in Europe has quite as much grass as Ireland.

27. Comparing Climate Data
Cork, Ireland and Edmonton, Alberta, in Canada are close to the same latitude
Cork is 51°47'N
Edmonton is 53° 34' N
Find the following for Cork, Ireland
Average daily high and low temperatures for Jan. ____ ____
Average daily high and low temperatures for July ____ ____
Temp. variation for winter to summer (hi/low) ____ ____
Average Precipitation for January and July
Find the following for Edmonton, Alberta (you will have to convert Celsius to Fahrenheit and mm to inches)
Temp. variation for winter to summer (hi/low) ____ ____
Average Precipitation for January and July ____ ____
Why are the climates for these two cities so different? (Read Ch 21.7, pg )

28. Comparing Climate Data
Cork, Ireland and Edmonton, Alberta, in Canada are close to the same latitude
Cork is 51°47'N
Edmonton is 53° 34' N)
Compare the climates for each using the graphs provided. You will have to convert Celsius to Fahrenheit and mm to inches to make comparison!
Coldest month and average day and night temperatures (data is already averaged!)
Warmest month and average day and night temperatures (data is already averaged)
Average summer high and low temperatures (you average the temperature over three summer months)
Average winter high and low and temperatures (you average the temperature over three winter months)
Temperature Mean for day and night (average 12 day and 12 night temperatures)
Month with greatest precipitation and least precipitation
Precipitation variation (amount of change from highest to lowest)—difference between highest and lowest
Temperature variation (amount of change from highest to lowest average day and night temperatures)
Why are the climates for these two cities different? (read attachment on-line)

29. Changing Angle of Sunlight
Reason for the Seasons 2
Changing Angle of Sunlight
The hemisphere tilted toward the Sun receives sunlight at higher angles than the hemisphere tilted away from the Sun.
Higher insolation angle means greater intensity of radiant energy (the sun shines more directly on a smaller area).
Summer in Northern Hemisphere

30. Identify the Seasons and the Equinox or Solstice, and comment about the number of daylight vs. night hours
Season _________
Equinox or Solstice
_________
Season _________
Equinox or Solstice
Season _________
Equinox or Solstice
Season ________
Equinox or Solstice

31. Identify the Seasons and the Equinox or Solstice
Equal day and night—12hr and 12 hr
Season _________
Equinox or Solstice
spring
Less daylight hours, more night hours
Less night hours, more daylight hours
winter
Season _________
Equinox or Solstice
summer
Season _________
Equinox or Solstice
fall
Season _________
Equinox or Solstice

32. FUNCTION OF A REFRIGERATOR
                              
Deposit unwanted Thermal Energy on the outside
Remove unwanted Thermal Energy from inside
By condensation
By evaporation

33. HOW DO AIR CONDITIONERS AND REFRIGERATORS WORK?
Evaporation of refrigerant removes thermal energy from inside.
Evaporation occurs when liquid refrigerant is allowed to expand (pressure release—lowers vaporization point—heat drawn from food causes evaporation)
Condensation of refrigerant releases thermal energy to the outside
Work must be done by the compressor to compress the refrigerant gas so that the thermal energy drawn from food is released outside when the gas is forced to condense under pressure)

34. 22. How do natural systems tend to proceed?

35. 24.7 Entropy
According to the second law of thermodynamics, in the long run, the entropy of a system always increases for natural processes. 35

36. 24.6 Order Tends to Disorder
Natural systems tend to proceed toward a state of greater disorder.
The universe trends from a higher state to a lower state of organization.
Examples:
Air flows from high to low pressure
Heat flows from hot to cold 36

37. 24.7 Entropy
Entropy is the measure of the amount of disorder in a system.
Disorder increases; entropy increases. 37

38. 24.7 Entropy
This run-down house demonstrates entropy. Without continual maintenance, the house will eventually fall apart. 38