Test 9 Objective 5

1. Heat engines use thermal energy to heat water that forms vapor.  The vapor escapes through one tube to push a wheel.
     http://www.chemistry.wustl.edu/~courses/genchem/Tutorials/Fridge/engine.htm

2. And I quote: "In an internal combustion engine, a working fluid is heated and expanded to produce power, captured in a cylinder and piston or in a turbine or similar system, and this heating and expansion is produced by burning fuel inside the expansion chamber.

In an external combustion engine, the working fluid is heated by burning fuel, then introduced into the expansion chamber to produce power."

http://wiki.answers.com/Q/Difference_between_internal_combustion_engines_and_external_combustion_engines

3. An internal combustion chamber is more efficient than an external and it won't overheat as easily because part of the design itself is to expand.

4.  The warm air is depleted leaving cold air.

5.  The warm air would make its way back into the fridge.