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Thermodynamics Unit Study Guide Chap. 21-24
Vocabulary
Temperature
Heat
Internal energy
Thermal equilibrium
Specific heat capacity
Convection
Conduction
Radiation
Heat of fusion
Heat of vaporization
Thermal Expansion
Adiabatic
Heat engine
Entropy
Thermodynamics
Problems
1. The hottest temperature ever recorded on a planet was 864 ºF on Venus by
the Soviet Venera probe and the U.S. Pioneer probe. The coldest place in the
solar system is Pluto where the temperature is estimated at -360.0 ºF.
Calculate each of these temperatures in degrees Celsius and Kelvin. (F =
(5/9)xC + 32).
5/9 x 864 + 32 = 512 ºC + 273 = 785 K
5/9 x -360 F +32 = -168 ºC + 273 = 105 K
2. A man consumes 2,500 Calories (food calories) in one day assuming that all of
this energy was used, and converted into heat, how much heat (in J/s) did he
give off that day?
2500 Cal
Day
X
1 day
24 hr
1 hr
3600 s
4.18J
1 cal
= .12 J/s
3. Calculate the number of calories of heat needed to change 340 mL of water by
50  C. Recall that 100 mL of water = 100 g of water.
17,000 calories or 17 Calories
4. A 50 gram piece of aluminum is heated to 100C and then dropped into cool
water where the aluminum’s temperature drops to 30C. How many calories
does the aluminum loose to the water? (Specific heat capacity Al = 0.215
cal/gC).
Q=mcT = 50g x .215 cal/gC x 70 = 752.5 calories
5. Calculate the Ideal efficiency of a heat engine that takes in energy at 450 K
and expels it to a reservoir at 60 K.
450-60/450 x 100 = 86.6 %
6. Circle the letter that best describes what happens when heat is added to a
system.
a. Much of it is destroyed immediately
b. It transforms to an equal amount of some other form of energy.
c. Much of it is lost
d. It is used to overcome friction
7. Is the following sentence true or false? The compression and expansion of
gases within the cylinders of an automobile engine is nearly adiabatic.
__TRUE TRUE__
8. What happens to a gas when it adiabatically expands and does work on its
surroundings? It loses internal energy and cools down
9. Circle the letter that describes the adiabatic form of the first law of
thermodynamics.
a. pressure = constant
b. energy out > energy in
c. change in air temperature is directly proportional to the pressure
change
d. energy in = energy out + work
Use the illustration below to answer the next question.
10.
Circle the letter that describes the process that occurs to create the
warm wind.
a. adiabatic expansion b. adiabatic compression c. isobaric contraction
d. thermal gain from land
11.
Circle the letter of the thermodynamic law that states heat will never of
itself flow from a cold object to a hot object.
a. 1st Law
b. 2nd law
c. 3rd law
d. 4th law
12.
Is the following sentence true or false? Many heat engines are able to
convert all heat input into mechanical energy output. FALSE
13.
Is the following sentence true or false? No heat engine can have an ideal
efficiency of 100%. TRUE TRUE
14.
Circle the letter that best describes how the second law of
thermodynamics applies to order and disorder.
a. For all systems, overall order is constant.
b. Natural systems tend toward a state of greater disorder.
c. Natural systems are equally likely to become more ordered or more
disordered
d. All natural systems tend toward increasing order
15.
A sample of gas is contained in a sealed flask. Circle the letter with the
greatest disorder.
a. The sample at 25 C in the sealed flask
b. The sample at 50 C in the sealed flask
c. The sample immediately after opening the flask
d. The sample after it expands to fill the room
16.
more
a.
b.
c.
d.
Circle the letter of each example of increasing entropy. There may be
than one answer.
Gas molecules escaping from a bottle
An unattended house breaking down
A plant using energy from the sun to form new cells
A breeze blowing papers off of your desk