# Thermodynamics Review KEY

Document Sample

```					                                             Thermodynamics Review
1.   What is heat and where does it come from? ENERGY TRANSFER

2.   How does heating and cooling work? ENERGY IS TRANSFERRED FROM HIGHER TEMPERATURE TO LOWER TEMPERATURE.

3.   When something cools down, what is it losing or gaining? SYSTEM IS LOSING HEAT

4.   Is heat the same thing as temperature? HEAT IS TOTAL THERMAL ENERGY; TEMPERATURE IS THE MEASURE OF THE
AVERAGE KINETIC ENERGY
5.
6.   How does a thermometer measure temperature? TWO OBJECTS REACH THERMAL EQUILIBRIUM

7.   What is energy and where does it come from? ENERGY IS TRANSFERRED.

8.   What is meant by energy conservation? ENERGY CANNOT BE CREATED OR DESTROYED.

9.   What is the first law of thermodynamics and how does it relate to question number 8? INTERNAL ENERGY CHANGE IS
EQUAL TO HEAT TRANSFERRED AND WORK DONE ON OR BY THE SYSTEM

10. How do we measure heat and energy? UNIT OF MEASURE JOULES

11. Consider two samples of different gases. One sample consists of helium atoms and the other sample consists of diatomic
oxygen molecules. If the samples are at the same temperature, will the particles within the sample have the same average
2
speed? TEMPERATURE IS MEASURE OF AVG KENETIC ENERGY OR ½ MV HEAVIER MASS LOWER VELOCITY

12. The particles in a sample of table salt (sodium chloride) are not free to move about. They are locked in place in a structure
known as a crystal lattice. Can the particles of sodium chloride possess kinetic energy? SOLIDS VIBRATE AND DO POSSESS
KINETIC ENERGY

13.       For each of the following designations of a system and a surroundings, identify the direction of heat flow as being
from the system to the surroundings or from the surroundings to the system.
System                                   Surroundings                                Dir'n of Heat Transfer
14. Living Room (T=78°F)                 Outside Air(T=94°F)                         SURROUNDINGS TO SYSTEM
15. b. Living Room(T=78°F)               Attic(T=120°F)                              SURROUNDINGS TO SYSTEM
16. c. Attic(T=120°F)                    Outside Air(T=94°F)                         SYSTEM TO SURROUNDINGS

17. A chemistry teacher claims that the heat content of a particular substance is 246 kJ/mol. Is the chemistry teacher claiming
that the substance contains heat? Explain what it meant by this claim. SUBSTANCES DO NOT CONTAIN HEAT.
18. Explain why high quality thermos bottles have a vacuum lining as a major component of their insulating ability.
VACUUM HAVE NO PARTICLES THEREFORE NO HEAT CAN BE TRANSFERRED BY CONDUCTION OR CONVECTION
19. Consider Object A which has a temperature of 65°C and Object B which has a temperature of 15°C. The two objects are
placed next to each other and the little bangers begin colliding. Will any of the collisions result in the transfer of energy
from Object B to Object A? Explain. TEMPERATURE IS A MEASURE OF AVERAGE KENETIC ENERGY THEREFOR THERE COULD
BE A PARTICLE FROM OBJECT B THAT HAS MORE ENERGY THAN OBJECT A
20. Suppose that Object A and Object B (from the previous problem) have reached a thermal equilibrium. Do the particles of
the two objects still collide with each other? If so, do any of the collisions result in the transfer of energy between the two
objects? Explain
21. Water has an unusually high specific heat capacity. Which one of the following statements logically follows from this fact?

22. Compared to other substances, hot water causes severe burns because it is a good conductor of heat           FALSE

23. Compared to other substances, water will quickly warm up to high temperatures when heated.                   FALSE

24. Compared to other substances, it takes a considerable amount of heat for a sample of water to change its temperature by a
small amount.                                                                                            TRUE

25. Explain why large bodies of water such as Lake Michigan can be quite chilly in early July despite the outdoor air
temperatures being near or above 90°F (32°C). HAS NOT REACHED THERMAL EQUALIBRIUM

The table below describes a thermal process for a variety of objects (indicated by bold-faced text). For each description, indicate
if heat is gained or lost by the object and whether Q for the indicated object is a positive or negative value.

Process Heat Gained or Heat Lost? Q: + or -?

26. An ice cube is placed into a glass of room               ICE CUBE +
temperature lemonade in order to cool the beverage down.

27. A cold glass of lemonade sits on the picnic table              LEMONADE +
in the hot afternoon sun and warms up to 32°F.

28. The burners on an electric stove are turned off                BURNERS -
and gradually cool down to room temperature.

29. The teacher removes a large chunk of dry ice from              DRY ICE -
a thermos and places it into water. The dry ice sublimes,
producing gaseous carbon dioxide.

30. Water vapor in the humidified air strikes the window and
turns to a dew drop (drop of liquid water).                    WATER VAPOR        -

31. An 11.98-gram sample of zinc metal is placed in a hot water bath and warmed to 78.4°C. It is then removed and placed into
a Styrofoam cup containing 50.0 mL of room temperature water (T=27.0°C; density = 1.00 g/mL). The water warms to a
temperature of 28.1°C. Determine the specific heat capacity of the zinc.

32.
33. Determine the amount of heat required to increase the temperature of a 3.82-gram sample of para-dichlorobenzene from
54°C to 75°C. Para-dichlorobenzene has a melting point of 54°C, a heat of fusion of 124 J/g and specific heat capacities of
1.01 J/g/°C (solid state) and 1.19 J/g/°C (liquid state).

34. A large paraffin candle has a mass of 96.83 gram. A metal cup with 100.0 mL of water at 16.2°C absorbs the heat from the
burning candle and increases its temperature to 35.7°C. Once the burning is ceased, the temperature of the water was
35.7°C and the paraffin had a mass of 96.14 gram. Determine the heat of combustion of paraffin in kJ/gram. GIVEN: density
of water = 1.0 g/mL

```
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
 views: 7 posted: 9/29/2012 language: Unknown pages: 2