1. Heat engines played a key role in the development of the modern industrial world. Steam locomotives were an important early use of the steam engine. Electric power plants today use steam turbines.

2. 16.3 Key Questions
What are the two main types of heat engines?
How do most heating systems distribute thermal energy?
How does a heat pump reverse the normal flow of heat?

3. external combustion engine—an engine that
16.3 Key Questions
The two main types of heat engines are the __________________ combustion engine and the __________________ combustion engine.
external combustion engine—an engine that
burns fuel _____________ the engine.
internal combustion engine—an engine that
external
internal
outside
inside

4. External Combustion Engine
Heat Engines
External Combustion Engine
A steam engine is an external combustion engine—an engine that burns fuel outside the engine.
Thomas _________________ developed the first practical steam engine in 1712 to pump ________ out of coal mines.
James ___________ designed an engine in 1765 that operated at a higher temperature and was more efficient.
Newcomen
water
Watt

5. Heat Engines
When the valve in a steam engine slides, steam is trapped in the cylinder. The steam expands and cools as it pushes the _____________ to the left.
piston
Hot steam in
Slide valve
Exhaust steam out
Valve rod
Piston rod
Cylinder
Piston

6. Heat Engines
Most __________ use an internal combustion engine that burns gasoline. They involve a piston that moves ________________ in a cylinder.
cars
up and down
Intake valve
Spark plug
Exhaust valve
Air-fuel mixture
Cylinder
Exhaust gases
Piston
Intake stroke
Compression Stroke
Power stroke
Exhaust stroke

7. Heat Engines
The linear motion of each stroke, is converted into _________________ motion of the crankshaft, which is connected to the transmission and wheels
rotary
Intake valve
Spark plug
Exhaust valve
Air-fuel mixture
Cylinder
Exhaust gases
Piston
Intake stroke
Compression Stroke
Power stroke
Exhaust stroke

8. Intake Stroke - ________ and _________ enter the cylinder
Heat Engines
Intake Stroke - ________ and _________ enter the cylinder
air
fuel
Intake valve
Spark plug
Exhaust valve
Air-fuel mixture
Cylinder
Exhaust gases
Piston
Intake stroke
Compression Stroke
Power stroke
Exhaust stroke

9. Compression Stroke – the piston _____________ the fuel-air mixture.
Heat Engines
Compression Stroke – the piston _____________ the fuel-air mixture.
compresses
Intake valve
Spark plug
Exhaust valve
Air-fuel mixture
Cylinder
Exhaust gases
Piston
Intake stroke
Compression Stroke
Power stroke
Exhaust stroke

10. Heat Engines
Power Stroke – A spark plug _____________ and _________ the mixture. The hot gas then expands and drives the piston ____________.
ignites
heats
down
Intake valve
Spark plug
Exhaust valve
Air-fuel mixture
Cylinder
Exhaust gases
Piston
Intake stroke
Compression Stroke
Power stroke
Exhaust stroke

11. Heat Engines
Exhaust Stroke – Gas ______________ the cylinder, and the cycle repeats
exits
Intake valve
Spark plug
Exhaust valve
Air-fuel mixture
Cylinder
Exhaust gases
Piston
Intake stroke
Compression Stroke
Power stroke
Exhaust stroke

12. Heat Engines
Gasoline engines are more efficient than old-fashioned steam engines, but they still are ______ very efficient.
Only about _____ of the energy in a gasoline engine is converted to work. The rest turns into ________________.
NOT
1/3
waste-heat

13. Most heating systems use _______________ to distribute thermal energy.
convection
A central heating system heats many rooms from one ______________ location.
Heating systems differ in how they transfer thermal energy to the rest of the building.
central

14. Heating Systems
Thermostat
Hot-Water Heating
Water heated by a boiler circulates through ________________ in each room, transferring thermal energy
Radiator
Exhaust vent
Expansion tank
radiators
Boiler
Circulating pump

15. Heating Systems Steam Heating
Steam heating is very similar to hot-water heating except that ___________ is used instead of hot water.
Steam heating often is used in _____________ buildings or when many buildings are heated from one central location.
steam
old

16. Electric Baseboard Heating
Heating Systems
Electric Baseboard Heating
An electric baseboard heater uses _________________ energy to heat a room.
A ________________ is used to convert electrical energy to thermal energy.
The ______________ heats the air near it by conduction and radiation.
Convection circulates the warm air to heat the room.
electrical
conductor
hot coil

17. The hot air _______ as cooler, denser air in the room ______
Heating Systems
Forced-Air Heating
Fans are used to circulate warm air through __________ to the rooms in a building
The hot air _______ as cooler, denser air in the room ______
Hot air rises
Cool air sinks
Supply vent
ducts
Return vent
Chimney
Duct
rises
Furnace
sinks

18. Cooling Systems
A heat pump is a device that _____________ the normal flow of thermal energy. This is done by circulating a ___________________ through tubing.
reverses
refrigerant
A refrigerant is a fluid that ________________ and ________________ inside the tubing of a heat pump.
When the refrigerant absorbs heat, it vaporizes, or turns into a ____________.
When the refrigerant gives off heat, it condenses, or turns back into a ____________.
vaporizes
condenses
gas
liquid

19. Cooling Systems Refrigerators
A refrigerator is a heat pump—it transfers thermal energy from the ____________ food compartment to the __________room.
A ______________ must do work to move refrigerant through tubing inside the refrigerator walls.
_____________ of tubing underneath or behind the refrigerator _____________ heat absorbed from the food compartment to the surroundings of the kitchen.
cold
warm
motor
Coils
release

20. Cooling Systems
When a refrigerator door is open, some thermal energy from the room _________ the refrigerator.
But __________ thermal energy leaves the refrigerator through the coils because it has to work harder
enters
more
Temperature in room: 25°C
Temperature in refrigerator: 3°C

21. Cooling Systems
In a window air conditioner, outside air is heated as a fan blows it through the condenser coil.
Condenser coil Vapor cools to liquid as heat is removed.
Warm air out
Cold air out
Compressor
Expansion valve Pressure drops, causing liquid refrigerant to become cold.
Warm air in
Evaporator coil Liquid absorbs heat to become vapor.

22. Assessment Questions
Only about one-third of the energy in gasoline is converted to work in an internal combustion engine. The rest of the chemical energy is
lost as unused mechanical energy.
destroyed by the engine.
converted to potential energy.
discharged as waste heat.

23. How is a room heated by an electric baseboard heating system?
Assessment Questions
How is a room heated by an electric baseboard heating system?
Water heated by a boiler circulates through radiators
Fans are used to circulate warm air through ducts
A hot coil heats air by conduction and radiation
Steam-heated radiators transfer heat to rooms

24. How do refrigerators reverse the normal flow of heat?
Assessment Questions
How do refrigerators reverse the normal flow of heat?
moving cool air from outside to inside the refrigerator
separating warm atoms from cool atoms
By moving a refrigerant through tubing inside the refrigerator walls
By releasing less energy than what enters the refrigerator