Unit 8 HEATING&COOLING CURVES QUESTION BANK

Unit 8 HEATING&COOLING CURVESQUESTION BANK

A) Both potential energy and average kinetic energyincrease.

B) Both potential energy and average kinetic energydecrease.

C) Potential energy increases and average kineticenergy remains the same.

D) Potential energy remains the same and averagekinetic energy increases.

1. The heating curve below represents a sample of asubstance starting as a solid below its melting pointand being heated over a period of time.

Which statement describes the energy of the particlesin this sample during interval DE?

A) The potential energy of the particles increases.B) The potential energy of the particles decreases.C) The average kinetic energy of the particles increases.D) The average kinetic energy of the particles decreases.

2. The graph below represents the relationship between time and temperature as heat is added at aconstant rate to a sample of a substance.

During interval AB which energy change occurs for the particles in this sample?

HEATING&COOLING CURVES

A) AB and BC B) AB and CDC) DE and BC D) DE and EF

3. Given the cooling curve of a substance:

During which intervals is potential energy decreasingand average kinetic energy remaining constant?

A) AC B) BC C) CD D) DF

4. Given the diagram representing a heating curve for asubstance:

During which time interval is the average kineticenergy of the particles of the substance constant whilethe potential energy of the particles increases?


A) Average kinetic energy increases, and potential energy remains the same.B) Average kinetic energy decreases, and potential energy remains the same.C) Average kinetic energy remains the same, and potential energy increases.D) Average kinetic energy remains the same, and potential energy decreases

5. The graph below represents the uniform heating of a sample of a substance starting as a solid below itsmelting point.

Which statement describes what happens to the energy of the particles of the sample during timeinterval DE?

A) Potential energy decreases and average kinetic energy increases.B) Potential energy increases and average kinetic energy increases.C) Potential energy increases and average kinetic energy remains the same.D) Potential energy remains the same and average kinetic energy increases.

6. The graph below represents the relationship between temperature and time as heat is added to a sampleof H2O

Which statement correctly describes the energy of the particles of the sample during interval BC?


A) 50°C and 3 min B) 50°C and 5 minC) 110°C and 4 min D) 110°C and 14 min

7. Starting as a solid, a sample of a substance is heatedat a constant rate. The graph below shows the changesin temperature of this sample.

What is the melting point of the sample and the totaltime required to completely melt the sample after ithas reached its melting point?

A) and B) and C) and D) and

8. The graph below represents the uniform heating of asubstance, starting below its melting point, when thesubstance is solid.

Which line segments represent an increase in averagekinetic energy?

A) B) C) D)

9. The graph below represents the uniform heating of asubstance, starting with the substance as a solid belowits melting point.

Which line segment represents an increase inpotential energy and no change in average kineticenergy?

A) 30°C B) 55°CC) 90°C D) 120°C

10. The graph below represents the heating curve of asubstance that starts as a solid below its freezingpoint.

What is the melting point of this substance?


A)

B)

C)

D)

11. Which graph could represent the uniform cooling ofa substance, starting with the gaseous phase andending with the solid phase?


A) 32°C B) 54°C C) 62°C D) 100°C

12. The table below shows the data collected by a student as heat was applied at a constant rate to a solidbelow its freezing point.

What is the boiling point of this substance?

A) AB B) BC C) CD D) DE

13. The graph below represents the uniform cooling of asubstance, starting with the substance as a gas aboveits boiling point.

During which interval is the substance completely inthe liquid phase? A) AB and CD B) BC and DE

C) AB and EF D) CD and EF

14. The graph below represents the uniform cooling ofwater at 1 atmosphere, starting with water as a gasabove its boiling point.

Which segments of the cooling curve represent thefixed points on a thermometer?


A) 70.°C B) 59°C C) 53°C D) 48°C

15. A student obtained the following data while cooling a substance. The substance was originally in theliquid phase at a temperature below its boiling point.

What is the freezing point of the substance?

Base your answers to questions 16 and 17 on thegraph below, which represents uniform cooling of asample of a pure substance, starting as a gas.

A) E and F B) B and CC) C and D D) D and E

16. Solid and liquid phases can exist in equilibriumbetween points

A) 10°C B) 60°CC) 120°C D) 180°C

17. The boiling point of the substance is

A) Its melting point is 45ºC.B) Its boiling point is 45ºC.C) Its melting point is 25ºC.D) Its boiling point is 25ºC.

18. As a solid is heated, its temperature increases from10ºC to 25ºC, remains at 25ºC for 5 minutes, andthen increases to beyond 45ºC. Based on thisinformation, what conclusion can be drawn aboutthe substance?

A) 42°C B) 53°C C) 58°C D) 65°C

19. A student observing the behavior ofparadichlorobenzene first heats 10 grams of thesubstance in a hot water bath until it is completelyliquefied. The following data are recorded asparadichlorobenzene cools.

What is the freezing point of paradichlorobenzene?


A) A and B B) B and DC) A and C D) C and D

20. The graph below represents the relationship betweentemperature and time as heat is added uniformly to asubstance, starting when the substance is a solidbelow its melting point.

Which portions of the graph represent times whenheat is absorbed and potential energy increases whilekinetic energy remains constant?

A) 6 min B) 10 minC) 8 min D) 4 min

21. The graph below was constructed by a student toshow the relationship between temperature and timeas heat was uniformly added to a solid below itsmelting point.

What is the total length of time that the solid phaseexisted with the liquid phase?

A) B)

C) D)

22. Which graph best represents a change of phase froma gas to a solid?

A) 0°C B) 20°C C) 70°C D) 40°C

23. The graph below represents changes of state for anunknown substance.

What is the boiling temperature of the substance?


24. Base your answer to the following question on the information below and on your knowledge ofchemistry.

In the late 19th century, the Hall-Herroult process was invented as an inexpensive way toproduce aluminum. In this process, extracted from bauxite is dissolved in in agraphite-lined tank, as shown in the diagram below. The products are carbon dioxide and moltenaluminum metal.

What is the melting point of the substance that collects at the bottom of the tank?

A) fusion B) depositionC) saponification D) decomposition

25. A gas changes directly to a solid during

A) the ice cubes to the airB) the beaker to the airC) the water to the ice cubesD) the water to the beaker

26. A beaker with water and the surrounding air are allat 24°C. After ice cubes are placed in the water, heatis transferred from

A) iridium B) osmiumC) tantalum D) tungsten

27. Which element has a melting point higher than themelting point of rhenium?

A) freezing and meltingB) freezing and vaporizationC) decomposition and meltingD) decomposition and combustion

28. Which processes represent one chemical change andone physical change?

A) Both the ice cube and the water lose heatenergy.

B) Both the ice cube and the water gain heatenergy.

C) The ice cube gains heat energy and the waterloses heat energy.

D) The ice cube loses heat energy and the watergains heat energy.

29. Which statement describes the transfer of heatenergy that occurs when an ice cube is added to aninsulated container with 100 milliliters of water at25°C?

A) 874°C B) 601°CC) 328°C D) 0°C

30. At which Celsius temperature does lead change froma solid to a liquid?


A) AB B) BC C) DE D) EF

31. The graph below represents the uniform heating of asubstance, starting with the substance as a solidbelow its melting point.

Which segment of the graph represents a time whenboth the solid and liquid phases are present?

A) It changes from solid to liquid, and heat isabsorbed.

B) It changes from solid to liquid, and heat isreleased.

C) It changes from liquid to solid, and heat isabsorbed.

D) It changes from liquid to solid, and heat isreleased.

32. What occurs when a substance melts?

A) 1°C B) 12°CC) 60°C D) 100°C

33. The diagram above represents the uniform heating ofa substance that is a solid at t0. What is the freezingpoint of the substance?

A) EF B) BC C) CD D) DE

34. The graph below represents the uniform cooling of asample of a substance, starting with the substance asa gas above its boiling point.

Which segment of the curve represents a time whenboth the liquid and the solid phases are present?

A) decreases B) increasesC) remains the same

35. When heat energy is lost by a pure substance at itsfreezing point, its potential energy

A) sublimation point B) vaporization pointC) boiling point D) melting point

36. At which point do a liquid and a solid exist atequilibrium?

A) B) C) D)

37. The graph below represents the uniform heating of asubstance from the solid to the gas phase.

Which line segment of the graph represents boiling?


38. As heat is added to a liquid that is boiling at constantpressure, the temperature of the liquid



39. As a liquid boils at its normal boiling point, itstemperature

Base your answers to questions 40 through 42 on the information below. Starting as a gas at 206°C, a sample of a substance is allowed to cool for 16 minutes. Thisprocess is represented by the cooling curve below.

40. What is the melting point of this substance?

41. At what time do the particles of this sample have the lowest average kinetic energy?

42. Using the key below, draw two particle diagrams to represent the two phases of the sample at minute4. Your response must include at least six particles for each diagram.


A) min 2 to min 4 B) min 4 to min 5 C) min 5 to min 7 D) min 7 to min 9

43. The cooling curve below represents the uniform cooling of a substance, starting at a temperatureabove its boiling point.

During which time interval does the substance exist as both a liquid and a solid?

Base your answers to questions 44 and 45 on the information below and on your knowledge ofchemistry.

A sample of a molecular substance starting as a gas at 206°C and 1 atm is allowed to cool for16 minutes. This process is represented by the cooling curve below.

44. Determine the number of minutes that the substance was in the liquid phase, only.

45. Describe what happens to the potential energy and the average kinetic energy of the molecules in thesample during interval DE.


Base your answers to questions 46 through 48 on the information below.

Given the heating curve where substance X starts as a solid below its melting point and is heateduniformly:

46. Identify the process that takes place during line segment DE of the heating curve.

47. Identify a line segment in which the average kinetic energy is increasing.

48. Describe, in terms of particle behavior or energy, what is happening to substance X during linesegment .


49. Base your answer to the following question on the heating curve below, which represents a substancestarting as a solid below its melting point and being heated at a constant rate over a period of time.

What is happening to the average kinetic energy of the particles during segment ?

50. Base your answer to the following question on the information below

A 5.00-gram sample of liquid ammonia is originally at 210. K. The diagram of the partialheating curve below represents the vaporization of the sample of ammonia at standard pressuredue to the addition of heat. The heat is not added at a constant rate.

Describe what is happening to both the potential energy and the average kinetic energy of themolecules in the ammonia sample during time interval BC. Your response must include both potentialenergy and average kinetic energy.


Base your answers to questions 51 and 52 on on the information below.

A 100.0-gram sample of NaCl(s) has an initial temperature of 0°C. A chemist measures thetemperature of the sample as it is heated. Heat is not added at a constant rate. The heating curve forthe sample is shown below.

51. Determine the temperature range over which the entire NaCl sample is a liquid.

52. Identify one line segment on the curve where the average kinetic energy of the particles of the NaClsample is changing.


Base your answers to questions 53 and 54 on the information below and on your knowledge ofchemistry.

A sample of a substance is a liquid at 65°C. The sample is heated uniformly to 125°C. Theheating curve for the sample at standard pressure is shown below.

53. Determine the boiling point of the sample at standard pressure.

54. State what happens to the potential energy of the particles of the sample during time interval BC.

Unit 8 HEATING&COOLING CURVES QUESTION BANK

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