Name KEY
20 points on your lab/quiz score
Thermodynamics Test Review KEY
1) Identify the following terms.
a. Energy: The ability to do work or transfer heat.
b. Kinetic energy: Energy an object possesses because of its motion. KE = ½mv2
c. Potential energy: Energy an object possesses because of distortion, position in a field of
force, or chemical bonds
i. (know the difference between distortion, chemical, gravitational—in your notes)
1. Distortion examples: compressed/stretched spring, stretched rubber band
2. Chemical examples: food or fuel; chemical energy is stored in bonds
3. Position in a field of force (ex. gravity): anything that can fall
d. Heat: A form of energy associated with the change in temperature of an object.
e. Entropy: A measure of the disorder of a system; ΔS
f. Gibbs free energy: The maximum amount of energy that can be coupled to another process
to do useful work. Abbreviated as ΔG
g. Enthalpy: The heat content of a system at constant pressure; ΔH
i. ΔH < 0  exothermic
ii. ΔH > 0  endothermic
h. Temperature: A measure of the average kinetic energy of the molecules in a system.
i. Law of Conservation of Energy: Energy cannot be created or destroyed in an ordinary
chemical reactio0n, but the form of energy can change.
2) Does entropy typically increase or decrease with time? Increases
3) Are heat and temperature the same?
Yes / No
4) Heat can be measured in joules or calories (basic units)
5) Heat flows from hot objects to cold objects.
6) Identify the three ways that heat can be transferred.
a. Transfer through electromagnetic waves radiation
b. Transfer through direct contact
conduction
c. Transfer through fluid motion of currents convection
7) Know the meanings of the following terms: melting, freezing, vaporization, evaporation, boiling,
condensation, sublimation, deposition.
8) Name one substance that is prone to sublimation. Dry ice (carbon dioxide)
Q = heat in calories or joules
m = mass in grams
c = specific heat in J/g°C or cal/g°C
ΔT = temperature change, final - initial
ΔHchange = enthalpy change for a phase change
9) Thermochemistry Equations
a. What equation do we use to relate heat, mass,
specific heat, and temperature change?
b. What equation do we use for phase changes?
(Melting at 0.0°C and for Vaporization at 100.
0°C)
Q = mcΔT
Q = mΔHchange
I’m only giving answers for these.
10) How many joules of heat are required to heat all the aluminum (specific heat = .902J/g°C) in a roll
of aluminum foil (500.0 g) from room temperature (25.0°C) to the temperature of a hot oven
(350.0°C)? Show all work for credit.
Q = 147000 J
11) An 18.7 g sample of platinum metal increases in temperature by 2.30°C when 5.70 J of heat are
added. What is the specific heat of platinum? Show all work for credit.
c = 0.133 J/g°C
12) A piece of silver (specific heat = .24 J/g°C) is cooled releasing 450 kJ of heat. It changes
temperature from 125.0°C to 10.0°C. What is the mass of this piece of silver? Show all work for
credit.
m = 16000 g
13) A 500.0 g piece of iron (specific heat = .11 cal/g°C) that starts off at 25°C is warmed by 330
calories of heat. What is the final temperature of the iron? Show all work for credit.
Final temperature = 31°C
14) How much heat would be given off by the condensation of 8.6 g of water? The heat of vaporization
of water is 2260 J/g. Show all work for credit.
Q = 19000 J
15) How much heat would be required to vaporize 100.0 g of helium, if the heat of vaporization of
helium is 20.9 J/g? Show all work for credit.
Q = 2090 J
16) Show all work on the following conversions.
a. 240 joules to calories
57 calories
b. 70 calories to joules
1 calorie = 4.18 joules
300 J
17) Hydrogen peroxide decomposes according to the following equation:
2 H2O2  O2 + 2 H2O
Determine the enthalpy change for this reaction. Show all work for
credit.
Substance
H2O2
O2
H2O
ΔHof (kJ/mol)
-191.17
0
-285.83
ΔH = -189.32 kJ
18) Is the reaction in question 17) endothermic or exothermic, and why? Exothermic, ΔH is negative.
19) Ethane undergoes combustion according to the following reaction: 2
C2H6 + 7 O2  6 H2O + 4 CO2
Determine the enthalpy change for this reaction. Show all work for
credit.
ΔH = -3205.21 kJ
Substance
C2H6
O2
H2O
CO2
ΔHof (kJ/mol)
-83.8
0
-285.83
-393.51
20) Is the reaction in question 19) endothermic or exothermic, and why? Exothermic, ΔH is negative.