Name: _____________________________________________
Physics: Unit 7 Test Review
Period:_______Date:
Answer the following showing ALL work including equations used, substitutions with units, and correct answer. For short
answer questions, just fill in the blank.
Vocabulary: Be able to define and/or explain the following terms.
1. Thermal Energy
2. Conduction
3. Convection
4. Radiation
5. Temperature
6. Heat
7. Specific heat
8. Calorimeter
9.
10.
11.
12.
13.
14.
15.
16.
Conservation of Energy
Boiling/Vaporization
Latent Heat of vaporization
Melting
Latent Heat of Fusion
First Law of Thermodynamics
Second Law of Thermodynamics
Entropy
Multiple Choice:
1. Which of the following is proportional to the kinetic energy of atoms and molecules?
a. elastic energy
b. temperature
c. potential energy
d. thermal equilibrium
2. Heat flow occurs between two bodies in thermal contact when they differ in which of the following properties?
a. mass
b. density
c. specific heat
d. temperature
3. If two small beakers of water, one at 20 ºC and one at 30 ºC, are emptied into a large beaker, what is the final temperature of
the water?
a. less than 20 ºC
b. between 20 ºC and 30 ºC
c. greater than 30 ºC
d. The water temperature will fluctuate.
4. Jacob takes six ice cubes from the freezer and puts four of them into a glass of water. He leaves two on the counter-top. He
stirs the water until the ice cubes are much smaller and have just stopped melting. What is the most likely temperature of the water
at this stage?
a. -10 ºC
b. 0 ºC
c. 5 ºC
d. 10 ºC
5. The ice cubes Jacob left on the counter are now almost completely melted and lying in a puddle of water. What is the most
likely temperature of these smaller ice cubes?
a. -10 ºC
b. 0 ºC
c. 5 ºC
d. 10 ºC
6. On the stove is a kettle full of water. The water has started to boil rapidly. The most likely temperature of the water is about
a. 88 ºC
b. 100 ºC
c. 110 ºC
d. None of the above
7. Five minutes later, the water in the kettle is still boiling. The most likely temperature of the water is about
a. 88 ºC
b. 100 ºC
c. 110 ºC
d. 120 ºC
8. What is the likely temperature of the steam above the boiling water in the kettle?
a. 88 ºC
b. 100 ºC
c. 110 ºC
d. 120 ºC
9. Erika takes two cups of water at 40 ºC and mixes them with one cup of water at 10 ºC. What is the most likely temperature of
the mixture?
a. 20 ºC
b. 25 ºC
c. 30 ºC
d. 50 ºC
10. Gracie takes a can of coke and plastic bottle of coke from the refrigerator, where they have both been overnight. She quickly
puts a thermometer in the can. The temperature is 7 ºC. What are the most likely temperatures of the plastic bottle and its
contents?
a. The are both less than 7 ºC
b. They are both at 7 ºC
c. They are both greater than 7 ºC
d. It depends on the size of the bottle
11. Melanie wants to know why people wear sweater in cold weather. Who is correct in terms of physics?
a. Kelly answers, “Because we look good in them.”
b. Ashlan adds, “It would be stupid to wear a sweater in the summer.”
c. Jeff says, “My dog wears a sweater.”
d. Sarah replies, “It reduces heat loss.”
12. Energy transferred as heat always moved from an object
a. at low temperature to an object at high temperature.
b. at high temperature to an object at low temperature.
c. at low kinetic energy to an object at high kinetic energy.
d. of higher mass to an object of lower mass.
13. Which law of thermodynamics deals with energy flow into less useful forms?
a. 1st law
b. 2nd law
c. 3rd law
d. 4th law
14. Which law of thermodynamics is a restatement of the law of conservation of energy?
a. 1st law
b. 2nd law
c. 3rd law
d. 4th law
15. During a phase change, which of the following does not change?
a. mass
b. heat
c. temperature
Problems:
1. Convert the following temperatures:
a) 20F to 50C 30oC
b) 20K to 50K
d. # of Joules
c) 100 C to 175oC 75oC
30K
d) 272k to 448K
75K
2.
The specific heat of methanol is 2450 J/kg  °C. Calculate the amount of heat that must be added to 0.25 kg of methanol to
raise its temperature from 15 C to 30 C.
𝐽
𝑄 = 𝑚𝐶Δ𝑇 = 0.25𝑘𝑔 ∗ 2450𝑔∙℃ ∗ 15℃ = 9188𝐽
3.
A 2.0 kg slab of concrete requires 11 kJ to raise its temperature from 23 C to 29 C. What is the specific heat of the
concrete? (Caution: units)
𝑄
11000𝐽
𝑄 = 𝑚𝐶Δ𝑇 ⟹ 𝐶 =
=
= 917𝐽
𝑚Δ𝑇 (2𝑘𝑔 ∗ 6℃)
4.
A sample of 0.0400 kg of iron at 30 C is placed in a container and allowed to cool. The specific heat of iron is 450 J/kgC
and it loses 180 J of heat energy. What is the final temperature of the system when it reaches thermal equilibrium?
𝑄
−180𝐽
𝑄 = 𝑚𝐶Δ𝑇 ⟹ Δ𝑇 =
=
= −10℃
𝑇𝑓 = 𝑇𝑖 + ∆𝑇 = 30℃ + (−10℃) = 20℃
𝑚C (0.04𝑘𝑔 ∗ 450 𝐽 )
𝑔∙℃
5.
6.
Iron has a heat of fusion of 2.66 x 106 J/kg. How much heat must be removed from 7.94 kg of molten iron at its freezing
point to turn it into solid iron at the same temperature?
𝐽
𝑄 = 𝐿𝑓 𝑚 = 2.66 × 106 𝑘𝑔 ∗ 7.94𝑘𝑔 = 2.1 × 107 𝐽
Ice has a specific heat of 2090 J/kg  K and a heat of fusion of 3.33 x 105 J/kg.
a) How much heat must be added to melt 2.0 kg of ice at 0.0  C
𝐽
𝑄𝑚𝑒𝑙𝑡 = 𝐿𝑓 𝑚 = 3.33 × 105 𝑘𝑔 ∗ 2.0𝑘𝑔 = 6.66 × 105 𝐽
b) How much heat must be added to raise the temperature from 0.0  to 30 C?
𝐽
𝑄ℎ𝑒𝑎𝑡𝑖𝑛𝑔 = 𝑚𝐶Δ𝑇 = 2.0𝑘𝑔 ∗ 4180𝑘𝑔∙℃ ∗ 30℃ = 2.51 × 105 𝐽
7.
c) What total amount of heat was needed to melt the ice and raise its temperature?
𝑄𝑡𝑜𝑡𝑎𝑙 = 𝑄𝑚𝑒𝑙𝑡 + 𝑄ℎ𝑒𝑎𝑡𝑖𝑛𝑔 = 6.66 × 105 𝐽 + 2.51 × 105 𝐽 = 9.17 × 105 𝐽
How much heat is required to change 500 g of ice at -50 C to steam at 115 C? Be complete. List all steps.
𝐽
𝐽
𝑄𝑖𝑐𝑒 = 𝑚𝐶Δ𝑇 = 500𝑔 ∗ 2.11𝑔∙℃ ∗ 50℃ = 52,750𝐽 𝑄𝑚𝑒𝑙𝑡 = 𝐿𝑓 𝑚 = 334𝑔 ∗ 500𝑔 = 167,000𝐽
𝐽
𝐽
𝑄𝑤𝑎𝑡𝑒𝑟 = 𝑚𝐶Δ𝑇 = 500𝑔 ∗ 4.18𝑔∙℃ ∗ 100℃ = 209,000𝐽 𝑄𝑣𝑎𝑝𝑜𝑟𝑖𝑧𝑒 = 𝐿𝑣 𝑚 = 2260𝑔 ∗ 500𝑔 = 1,130,000𝐽
𝐽
𝑄𝑔𝑎𝑠 = 𝑚𝐶Δ𝑇 = 500𝑔 ∗ 2.00𝑔∙℃ ∗ 15℃ = 15,000𝐽
𝑄𝑡𝑜𝑡𝑎𝑙 = 1,573,750𝐽