Heat and Internal Energy

Heat and Internal Energy

Explain how heat transfer and energy transformation make heat engines work S9FE - IVg -45

Multiple Choice

A system does no work even when heat is added to it. Which of the following may happen to the system?

• The system expands

• The internal energy of the system increases

Multiple Choice

The working substance used in most refrigerators is a _____________.

• Gas that is easy to liquefy

• Gas that is hard to liquefy

• Liquid that is easy to solidify

• Liquid that is hard to solidify

Multiple Choice

What do you call an object that does not significantly change in temperature and internal energy even when the heat is removed or added to it?

• Heat sink

• Reservoir

• Working Substance

• heat engine

Multiple Choice

What is the function of a heat engine?

• It converts thermal energy into chemical energy.

• It converts thermal energy to mechanical energy.

• It converts mechanical energy to chemical energy.

• It converts chemical energy to mechanical energy.

Multiple Choice

What is the correct sequence of four cycle-stroke of a gasoline engine?

I. Intake II. Power III. Exhaust IV. Compression

• I, II, III, IV

• I, IV, II, III

• II, III, IV, I

• I, III, IV, II

Second Law of Thermodynamics

Heat always naturally travels from an object of internal energy at a higher temperature to an object of internal energy at a lower temperature

• will need a continual input of energy from an external source for it to start and continuously happen.

Non-Spontaneous

• occurs naturally under certain conditions.

​Spontaneous

SPONTANEOUS AND

NON-SPONTANEOUS PROCESS

Multiple Choice

Ball rolling down the hill

• Spontaneous

• Non-Spontaneous

Multiple Choice

Ice melting at room temperature

• Spontaneous

• Non-Spontaneous

Multiple Choice

The rusting of iron at room temperature

• Spontaneous

• Non-Spontaneous

Multiple Choice

Is it impossible to have a NON-SPONTANEOUS PROCESS?

• Yes

• No

Second Law of Thermodynamics

It is impossible to construct an engine operating in a cycle that converts heat totally into mechanical energy to do an equivalent amount of work.

A refrigerator, working in a process of transporting heat from the cold to the hot reservoir is indeed a reversed heat engine!

​Refrigerators

A refrigerator is a heat engine in which work is done on a refrigerant substance to collect energy from a cold region and exhaust it in a higher temperature region, thereby cooling the cold region further.

A thermodynamic device that converts heat energy into mechanical energy is a heat engine.

Heat Engine

​

Second Law of Thermodynamics

• The natural direction of heat flow is from an object of higher temperature to an object of lower temperature.

• It is impossible to construct an engine operating in a cycle that converts heat totally into mechanical energy to do an equivalent amount of work.​