S6. (a) State what is meant by an ideal gas...

IB PHYSICS Name: DEVIL PHYSICS Period: Date: BADDEST CLASS ON CAMPUS TSOKOS CHAPTER 3 TEST REVIEW S1. Thermal energy is transferred through the glass windows of a house mainly by A. conduction. B. radiation. C. conduction and convection. D. radiation and convection. S3. When a gas in a cylinder is compressed at constant temperature by a piston, the pressure of the gas increases. Consider the following three statements. I. The rate at which the molecules collide with the piston increases. II. The average speed of the molecules increases. III. The molecules collide with each other more often. Which statement(s) correctly explain the increase in pressure? A. I only B. II only C. I and II only D. I and III only S6. (a) State what is meant by an ideal gas.......... (b) The internal volume of a gas cylinder is 2. 1 2 m 3. An ideal gas is pumped into the cylinder until the pressure becomes 2 MPa at a temperature of 17 C. Determine (i) the number of moles of gas in the cylinder; the number of gas atoms in the cylinder. (c) (i) Using your answers in (b), determine the average volume occupied by one gas atom. Estimate a value for the average separation of the gas atoms. 212 Test Review~Study Guide.Doc Updated: 17-Feb-12 Page 1 of 19

(Total 9 marks) S9. This question is about modeling the thermal processes involved when a person is running. When running, a person generates thermal energy but maintains approximately constant temperature. (a) Explain what thermal energy and temperature mean. Distinguish between the two concepts................... (4) The following simple model may be used to estimate the rise in temperature of a runner assuming no thermal energy is lost. A closed container holds 7 kg of water, representing the mass of the runner. The water is heated at a rate of 12 W for 3 minutes. This represents the energy generation in the runner. (b) (i) Show that the thermal energy generated by the heater is 2.2 1 6 J. (c) Calculate the temperature rise of the water, assuming no energy losses from the water. The specific heat capacity of water is 42 J kg 1 K 1. The temperature rise calculated in (b) would be dangerous for the runner. Outline three mechanisms, other than evaporation, by which the container in the model would transfer energy to its surroundings......................... A further process by which energy is lost from the runner is the evaporation of sweat. (d) (i) Describe, in terms of molecular behaviour, why evaporation causes cooling. (6) 212 Test Review~Study Guide.Doc Updated: 17-Feb-12 Page 2 of 19

Percentage of generated energy lost by sweating: 5% Specific latent heat of vaporization of sweat: 2.26 1 6 J kg 1 Using the information above, and your answer to (b) (i), estimate the mass of sweat evaporated from the runner. (iii) State and explain two factors that affect the rate of evaporation of sweat from the skin of the runner. (4) (Total 25 marks) S1. This question is about estimating the area of solar panels and the diameter of a wind turbine. It is suggested that a combination of solar power and wind power be used to provide the hot water system in a house. An active solar heater is to provide the energy to heat the water. A wind turbine is to provide the energy to pump the water. Solar heater The following data are available: (a) volume of hot water tank = 1.2 m 3 density of water = 1. 1 3 kg m 3 initial temperature of the water = 1 C final temperature of the water = 4 C specific heat capacity of water = 4.2 1 3 J kg 1 K 1 average power per unit area from the Sun =.8 kw m 2 time required to heat the water = 2. hours Using the above data, (i) (iii) deduce that 1.5 1 8 J of energy is required to heat the volume of water in the tank from 1 C to 4 C. estimate the minimum area of the solar panel needed to provide 1.5 1 8 J of energy in 2. hours. discuss whether, in this situation, using a solar panel to heat the water is a sensible method. 212 Test Review~Study Guide.Doc Updated: 17-Feb-12 Page 3 of 19

Wind turbine The following data are available: power of solar heater pump =.4 kw average local wind speed = 6. m s 1 average density of air = 1. kg m 3 (b) (i) Using the above data, estimate the minimum radius of the wind turbine needed to provide the power required to drive the solar heater pump. Discuss whether, in this situation, using a wind turbine to pump the water is a sensible method. (Total 1 marks) S17. The specific latent heat of fusion of a substance is defined as the amount of thermal energy required to change the phase of A. the substance at constant temperature. B. unit mass of the substance to liquid at constant temperature. C. unit mass of the substance at constant temperature. D. the substance to gas at constant temperature. S18. A fixed mass of an ideal gas is heated at constant volume. Which one of the following graphs best shows the variation with Celsius temperature t with pressure p of the gas? A. p B. p t / C t / C C. p D. p t / C t / C 212 Test Review~Study Guide.Doc Updated: 17-Feb-12 Page 4 of 19

S2. This question is about entropy changes. (a) State what is meant by an increase in entropy of a system....... (b) (c) State, in terms of entropy, the second law of thermodynamics.......... When a chicken develops inside an egg, the entropy of the egg and its contents decreases. Explain how this observation is consistent with the second law of thermodynamics.......... (Total 5 marks) S22. The distance between the C and 1 C marks on a mercury-in-glass thermometer is 2 cm. When the thermometer bulb is placed in a mixture of ice and salt, the mercury level is 4 cm below the C mark. The temperature of the mixture is A. +2 C. B. +5 C. C. 5 C. D. 2 C. S25. This question is about the change of phase (state) of ice. A quantity of crushed ice is removed from a freezer and placed in a calorimeter. Thermal energy is supplied to the ice at a constant rate. To ensure that all the ice is at the same temperature, it is continually stirred. The temperature of the contents of the calorimeter is recorded every 15 seconds. The graph below shows the variation with time t of the temperature θ of the contents of the calorimeter. (Uncertainties in the measured quantities are not shown.) 2 15 1 5 C 5 1 15 (a) 2 25 5 75 1 125 15 175 2 t / s On the graph above, mark with an X, the data point on the graph at which all the ice has just melted. 212 Test Review~Study Guide.Doc Updated: 17-Feb-12 Page 5 of 19

(b) Explain, with reference to the energy of the molecules, the constant temperature region of the graph................ The mass of the ice is.25 kg and the specific heat capacity of water is 42 J kg 1 K 1. (c) Use these data and data from the graph to (i) deduce that energy is supplied to the ice at the rate of about 53 W. (iii) determine the specific heat capacity of ice. determine the specific latent heat of fusion of ice. (Total 12 marks) S26. This question is about p V diagrams. The graph below shows the variation with volume of the pressure of a fixed mass of gas when it is compressed adiabatically and also when the same sample of gas is compressed isothermally. 7. C 6. 5. 5 pressure / x 1 Pa B 4. 3. (a) 2. 1. 2. 3. 4. volume / x 1 m 3 3 State and explain which line AB or AC represents the isothermal compression. A 5. 6. 212 Test Review~Study Guide.Doc Updated: 17-Feb-12 Page 6 of 19

(b) (c) (d)...... On the graph, shade the area that represents the difference in work done in the adiabatic change and in the isothermal change. Determine the difference in work done, as identified in (b)............. Use the first law of thermodynamics to explain the change in temperature during the adiabatic compression............. (Total 9 marks) S27. In one cycle of a heat engine, 3 J of energy is absorbed and 2 J of energy is ejected. The efficiency of the engine is A. B. C. D. 3. 2 2. 3 1. 2 1. 3 S28. A gas expands rapidly. The process is approximately A. isobaric. B. isothermal. C. adiabatic. D. isovolumetric. S3. As part of an experiment to determine the latent heat of vaporisation of water, a student boils some water in a beaker using an electric heater as shown below. beaker heater water The student notes two sources of error. 212 Test Review~Study Guide.Doc Updated: 17-Feb-12 Page 7 of 19

Error 1: thermal energy is lost from the sides of the beaker Error 2: as the water is boiling, water splashes out of the beaker Which of the following gives the correct effect of these two errors on the calculated value for the specific latent heat? Error 1 Error 2 A. Increase Decrease B. Increase No change C. Decrease Increase D. Decrease No change S31. This question is about specific heat capacity and specific latent heat. (a) Define specific heat capacity....... (b) Explain briefly why the specific heat capacity of different substances such as aluminium and water are not equal in value............. A quantity of water at temperature θ is placed in a pan and heated at a constant rate until some of the water has turned into steam. The boiling point of the water is 1 C. (c) (i) Using the axes below, draw a sketch-graph to show the variation with time t of the temperature θ of the water. (Note: this is a sketch-graph; you do not need to add any values to the axes.) 1 C C time at which heating starts time at which water starts to boil Describe in terms of energy changes, the molecular behaviour of water and steam during the heating process. t 212 Test Review~Study Guide.Doc Updated: 17-Feb-12 Page 8 of 19

(5) Thermal energy is supplied to the water in the pan for 1 minutes at a constant rate of 4 W. The thermal capacity of the pan is negligible. (d) (i) Deduce that the total energy supplied in 1 minutes is 2.4 1 5 J. (iii) Using the data below, estimate the mass of water turned into steam as a result of this heating process. initial mass of water =.3 kg initial temperature of the water θ = 2 C specific heat capacity of water = 4.2 1 3 J kg 1 K 1 specific latent heat of vaporization of water = 2.3 1 6 Jkg 1 Suggest one reason why this mass is an estimate. (Total 14 marks) S35. During an experiment, a solid is heated from 285 K to 298 K. Which one of the following gives the rise in temperature, in deg C, and the final temperature, in C, of the solid? Rise in temperature in deg C Final temperature in C A. 13 571 B. 13 25 C. 286 571 D. 286 25 S39. The diagram shows the pressure/volume (p/v) diagram for one cycle PQRS of an engine. p Q R S P In which sections of the cycle is work done on the engine? V 212 Test Review~Study Guide.Doc Updated: 17-Feb-12 Page 9 of 19

A. SP only B. PQ only C. SP and PQ only D. RS and SP only S4. The Kelvin temperature of an ideal gas is a measure of the A. average speed of the molecules. B. average momentum of the molecules. C. average kinetic energy of the molecules. D. average potential energy of the molecules. S41. The specific latent heat of vaporization of a substance is defined as the amount of thermal energy required to A. change a liquid to vapour at constant pressure. B. change a liquid to vapour at constant temperature. C. change unit mass of liquid to vapour at constant pressure. D. change unit mass of liquid to vapour at constant temperature. S42. A gas is contained in a cylinder fitted with a piston as shown below. gas piston When the gas is compressed rapidly by the piston its temperature rises because the molecules of the gas A. are squeezed closer together. B. collide with each other more frequently. C. collide with the walls of the container more frequently. D. gain energy from the moving piston. S43. This question is about thermal physics. (a) Explain why, when a liquid evaporates, the liquid cools unless thermal energy is supplied to it............. (b) (c) State two factors that cause an increase in the rate of evaporation of a liquid. 1.... 2.... Some data for ice and for water are given below. Specific heat capacity of ice = 2.1 1 3 J kg 1 K 1 Specific heat capacity of water = 4.2 1 3 J kg 1 K 1 Specific latent heat of fusion of ice = 3.3 1 5 J kg 1 A mass of 35 g of water at a temperature of 25 C is placed in a refrigerator that extracts thermal energy from the water at a rate of 86 W. Calculate the time taken for the water to become ice at 5. C....... 212 Test Review~Study Guide.Doc Updated: 17-Feb-12 Page 1 of 19

......... S45. This question is about ideal gases and specific heat capacity. (a) (i) State, in terms of kinetic theory, what is meant by an ideal gas. Explain why the internal energy of an ideal gas is kinetic energy only. (4) (Total 9 marks) A fixed mass of an ideal gas has a volume of 87 cm 3 at a pressure of 1. 1 5 Pa and a temperature of 2. C. The gas is heated at constant pressure to a temperature of 21. C. (b) (i) Calculate the change in volume of the gas. Determine the external work done during this process. (c) (i) Define specific heat capacity. (iii) Explain what happens to the molecules of an ideal gas when the temperature of the gas is increased at constant volume. Apply the first law of thermodynamics to show that, if the temperature of a gas is raised at constant pressure, the specific heat capacity of the gas is different from that when the temperature is raised at constant volume. (Total 17 marks) S48. Container X below has volume V and holds n moles of an ideal gas at kelvin temperature T. Container Y has volume 212 Test Review~Study Guide.Doc Updated: 17-Feb-12 Page 11 of 19

2V and holds 3n moles of an ideal gas also at kelvin temperature T. volume V temperature T n moles pressure P X volume V temperature T 3n moles pressure P Y container X container Y The pressure of the gas in X is P X and in Y is P Y. PX The ratio is P A. 2. 3 B. 3. 2 C. 5. D. 6. Y S49. This question is about an ideal gas. An ideal gas is contained in a cylinder fitted with a frictionless piston, as shown below. gas surface area A cylinder pressure p The piston has surface area A. A constant external pressure p acts on the piston. (a) Deduce that, for an increase in volume V of the gas, the external work done W is given by (b) W = p V............. The energy supplied to the gas for this increase in volume is found to be greater than p V. State and explain any change in the gas.......... S5. Which one of the following is a correct statement of the second law of thermodynamics? 212 Test Review~Study Guide.Doc Updated: 17-Feb-12 Page 12 of 19 (Total 5 marks)

A. When the state of a system changes its entropy increases. B. When the state of a system changes its entropy decreases. C. The total entropy of the universe is increasing with time. D. The total entropy of the universe is decreasing with time. S51. Expansion of a gas An ideal gas at an initial pressure of 4. 1 5 Pa is expanded isothermally from a volume of 3. m 3 to a volume of 5. m 3. (a) Calculate the final pressure of the gas....... (b) On the axes below draw a sketch graph to show the variation with volume V of the pressure p during this expansion. 5 p / 1 Pa 6 4 2 (c) 2 4 6 / m 3 Use the sketch graph in (b) to (i) estimate the work done by the gas during this process; explain why less work would be done if the gas were to expand adiabatically from the same initial state to the same final volume. (Total 7 marks) S54. Which of the following correctly shows the changes, if any, in the potential energy and in the kinetic energy of the molecules of a solid as it melts? 212 Test Review~Study Guide.Doc Updated: 17-Feb-12 Page 13 of 19

Potential energy Kinetic energy A. Decreases Increases B. Increases Stays the same C. Stays the same Decreases D. Stays the same Stays the same S57. This question is about thermodynamic processes. (a) State what is meant by the concept of internal energy of an ideal gas....... (b) The diagram below shows the variation with volume of the pressure of a fixed mass of an ideal gas. B pressure A C volume The change from B to C is an isothermal change at 546 K. At point A, the pressure of the gas is 1.1 the volume of the gas is 22. m 3 and the temperature of the gas is 273 K. (i) State the temperature of the gas at point C; Calculate the volume of the gas at point C. (c) For the change from B to C, 31.5 1 5 J of thermal energy is transferred to the gas. (i) State the work done in the change from A to B. Determine the work done during the change C to A. 1 5 Pa, 212 Test Review~Study Guide.Doc Updated: 17-Feb-12 Page 14 of 19

(iii) (iv) Explain whether the work in is done by the gas or on the gas. Determine the work done by the gas during one cycle ABCA. (Total 11 marks) S6. A fixed quantity of an ideal gas is compressed at constant temperature. The best explanation for the increase in pressure is that the molecules A. are moving faster. B. are colliding more frequently with the container walls. C. exert greater forces on each other. D. are colliding more frequently with each other. S61. This question is about temperature and internal energy. Two solid copper spheres, having different radii, undergo the same temperature change. A student states that the change in internal energy of the two objects would be the same. Briefly discuss this statement................ (Total 3 marks) S64. An ideal gas expands isothermally, doing 25 J of external work in the process. The thermal energy absorbed by the gas in this process is A. zero. B. less than 25 J. C. equal to 25 J. D. more than 25 J. S65. A well-insulated container is divided into two equal volumes by a wall. In one half there is an ideal gas and the other is a vacuum as shown below. gas vacuum gas The wall is now removed. Which one of the following correctly gives the changes, if any, that take place in the internal energy and entropy of the gas? Internal energy Entropy A. stays the same stays the same B. stays the same increases C. decreases stays the same 212 Test Review~Study Guide.Doc Updated: 17-Feb-12 Page 15 of 19

D. decreases increases S66. The molar mass of water is 18 g. The approximate number of water molecules in a glass of water is A. 1 22. B. 1 25. C. 1 28. D. 1 31. S68. An ideal gas is kept in a container of fixed volume at a temperature of 3 C and a pressure of 6. atm. The gas is heated at constant volume to a temperature of 33 C. pressure 6. atm temperature 3 C gas new pressure temperature 33 C gas The new pressure of the gas is about A..6 atm. B. 3. atm. C. 12 atm. D. 66 atm. S7. The entropy of a system is a measure of the system s A. disorder. B. mean energy. C. temperature. D. total energy. S72. The specific latent heat of fusion of a substance is the quantity of thermal energy required to convert, at constant temperature, A. a solid to a liquid. B. unit mass of solid to liquid. C. a liquid to a solid. D. unit mass of liquid to solid. S73. A sample of an ideal gas is contained in a cylinder. The volume of the gas is suddenly decreased. A student makes the following statements to explain the change in pressure of the gas. I. The average kinetic energy of the gas atoms increases. II. The atoms of the gas hit the walls of the cylinder more frequently. III. There are more atoms that are able to collide with the walls of the cylinder. Which of these statements is true? A. I and II only B. I and III only C. II and III only D. I, II and III S74. This question is about a heat engine. A quantity of an ideal gas is used as the working substance of a heat engine. The cycle of operation of the engine is shown in the p-v diagram below. 212 Test Review~Study Guide.Doc Updated: 17-Feb-12 Page 16 of 19

5 p / 1 Pa 12. A B 8. 4. C V / 1 m 2 4 6 The temperature of the gas at A is 3 K. (a) Calculate the temperature, at B, of the gas.......... (b) During the change A B the change in internal energy of the gas is 7.2 kj. Determine the amount of thermal energy transferred............. (c) State why, for the change B C, the change in the internal energy of the gas is numerically the same as that in (b)....... (d) The work done on the gas in the change C A is 2.6 kj. Calculate (i) the net work done in one cycle. -3 3 the efficiency. (Total 1 marks) S75. The graph shows the variation with pressure p of the volume V of a sample of gas. 212 Test Review~Study Guide.Doc Updated: 17-Feb-12 Page 17 of 19

V V 2 Y V X Z 1 p p 1 2 The work done during the change of state from X to Y is A. zero B. p 1 (V 2 V 1 ) C. p 2 V 2 p 1 V 1 D. 1 ( p 2 2 p1)( V2 V1 ) S77. Which of the following will not affect the rate of evaporation of a liquid? A. The temperature of the liquid B. The surface area of the liquid C. The mass of the liquid D. Convection currents of air above the liquid surface S78. The graph below shows the variation with absolute temperature T of the pressure p of one mole of an ideal gas having a volume V. R is the molar gas constant. p p T Which of the following is the best interpretation of the intercept on the temperature axis and the gradient of the graph? A. B. C. D. Intercept on temperature axis / K 273 273 Gradient of graph R V R V V R V R 212 Test Review~Study Guide.Doc Updated: 17-Feb-12 Page 18 of 19

S79. For any natural process, the second law of thermodynamics states that the total entropy of the universe A. always decreases. B. usually decreases but may increase. C. always increases. D. usually increases but may decrease. S8. A gas is contained in a cylinder fitted with a piston as shown below. When the gas is compressed rapidly by the piston its temperature rises because the molecules of the gas A. are squeezed closer together. B. collide with each other more frequently. C. collide with the walls of the container more frequently. D. gain energy from the moving piston. S82. The diagram shows the pressure / volume (p/v) diagram for one cycle PQRS of an engine. In which sections of the cycle is work done on the engine? A. SP only B. PQ only C. SP and PQ only D. RS and SP only 212 Test Review~Study Guide.Doc Updated: 17-Feb-12 Page 19 of 19