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6) A student is about to finish her carton of drink. The carton collapses as she sucks the last few drops.a)What changes,if any,are there toi)the total number of air molecules inside the arton,ii)the speed of the air molecules,iii)the space between the air molecules?b)Use you answer in(a) to explain why the... 顯示更多 6) A student is about to finish her carton of drink. The carton collapses as she sucks the last few drops. a)What changes,if any,are there to i)the total number of air molecules inside the arton, ii)the speed of the air molecules, iii)the space between the air molecules? b)Use you answer in(a) to explain why the acrton collapses. c)While keeping the carton collapsed,the opening of the carton is sealed with tape so that no air can travel into or out of the carton.Suggest a method to make the caton to regain its original shape.Explain your answer briefly. 9)A syringe containingcarbon dioxide gas at 20'C is laid on it side,with its nozzle closed.The volume of the gas is 50cm^3 and the pressure of the gas is equal to the atmospheric pressure.The weight of the piston is 1N and the radius is 1 cm.Assume that the piston in the syringe is very smooth. a)The gas is heated to 100'C .Explain why the piston moves,using the kinetic theory of gases. b)The piston stops moving once the volume of carbon dioxide increases to a certain value.Assume that the gas does notescape from the syringe and stays at 100'C. i)Explain why the piston stops,using the kinetic theory of gases. ii)Find the new volume of carbon dioxide. c)The syringe is turned so that it is vertical,with the nozzle at the bottom. i)The piston drops to a certain level.Explain briefly using the kinetic theory. ii)Find the new pressure and volume of carbon dioxide.Assume the temp. is maintained at 100'C. III)Draw a p-V graph showing the changes of the pressure and the volume of carbon dioxide when the piston drops.
最佳解答:
6. (a) The no. of air molecules decreases as some of them have been sucked together with the last few drops of liquid.(ii) The speed of air molecules remains unchanged, because speed is dependent on temperature only.(iii) The space between molecules remains the same after the carton collpases. (b) After sucking some air out, the pressure inside the carton decreases. The outside atmospheric pressure squeezes the carton, decreasing its volume until the pressure inside returns to atmospheric pressure. (c)(i) Heat the carton over a fire gently. The heat causes an increase in pressure inside the carton, thus forcing it to resume its original shape and volume. 9. (a) Air molecules gain excessive kinetic energy and move at higher speed, thus leads to an increase in pressure. (b) (i) Expansion of volume causes a decreases of pressure, because molecules need to travel longer distance before impact with the piston. WHen the pressure drops to that of atmosphere, movement of the piston then stops. (ii) Using ideal gas law, PV/T = constant(Po)(50)/(273+20) = (Po).V/(273+100) [where Po is the atmospheric pressure, and V is the new volume]. thus, V = 63.65 cm^3(c) (i) The piston has a weight of 1 N. Hence, it falls down, compressing the gas. As the volume is reduced, more frequent impact of molecules with the piston occurs, which increases the pressure. When the increase in pressure is able to balance the 1 N weight of the piston, its movement stops. (ii) Pressure due to weight of piston = 1/(pi x 0.1^2) N/m^2 = 31.83 N/m^2 New pressure = (Po+31.83) N/m2 = 101,032 N/m2 where Po, atmospheric pressure = 1.01 x 10^5 N/m2 (Po).(63.65) = (Po+31.83).V', where V' is the new volume solve for V' gives V' = 63.63 cm^3 (iii) SInce it is an isothermal process, the P-V diagram follows an isothermal line.
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f.4phy (gases)發問:
6) A student is about to finish her carton of drink. The carton collapses as she sucks the last few drops.a)What changes,if any,are there toi)the total number of air molecules inside the arton,ii)the speed of the air molecules,iii)the space between the air molecules?b)Use you answer in(a) to explain why the... 顯示更多 6) A student is about to finish her carton of drink. The carton collapses as she sucks the last few drops. a)What changes,if any,are there to i)the total number of air molecules inside the arton, ii)the speed of the air molecules, iii)the space between the air molecules? b)Use you answer in(a) to explain why the acrton collapses. c)While keeping the carton collapsed,the opening of the carton is sealed with tape so that no air can travel into or out of the carton.Suggest a method to make the caton to regain its original shape.Explain your answer briefly. 9)A syringe containingcarbon dioxide gas at 20'C is laid on it side,with its nozzle closed.The volume of the gas is 50cm^3 and the pressure of the gas is equal to the atmospheric pressure.The weight of the piston is 1N and the radius is 1 cm.Assume that the piston in the syringe is very smooth. a)The gas is heated to 100'C .Explain why the piston moves,using the kinetic theory of gases. b)The piston stops moving once the volume of carbon dioxide increases to a certain value.Assume that the gas does notescape from the syringe and stays at 100'C. i)Explain why the piston stops,using the kinetic theory of gases. ii)Find the new volume of carbon dioxide. c)The syringe is turned so that it is vertical,with the nozzle at the bottom. i)The piston drops to a certain level.Explain briefly using the kinetic theory. ii)Find the new pressure and volume of carbon dioxide.Assume the temp. is maintained at 100'C. III)Draw a p-V graph showing the changes of the pressure and the volume of carbon dioxide when the piston drops.
最佳解答:
6. (a) The no. of air molecules decreases as some of them have been sucked together with the last few drops of liquid.(ii) The speed of air molecules remains unchanged, because speed is dependent on temperature only.(iii) The space between molecules remains the same after the carton collpases. (b) After sucking some air out, the pressure inside the carton decreases. The outside atmospheric pressure squeezes the carton, decreasing its volume until the pressure inside returns to atmospheric pressure. (c)(i) Heat the carton over a fire gently. The heat causes an increase in pressure inside the carton, thus forcing it to resume its original shape and volume. 9. (a) Air molecules gain excessive kinetic energy and move at higher speed, thus leads to an increase in pressure. (b) (i) Expansion of volume causes a decreases of pressure, because molecules need to travel longer distance before impact with the piston. WHen the pressure drops to that of atmosphere, movement of the piston then stops. (ii) Using ideal gas law, PV/T = constant(Po)(50)/(273+20) = (Po).V/(273+100) [where Po is the atmospheric pressure, and V is the new volume]. thus, V = 63.65 cm^3(c) (i) The piston has a weight of 1 N. Hence, it falls down, compressing the gas. As the volume is reduced, more frequent impact of molecules with the piston occurs, which increases the pressure. When the increase in pressure is able to balance the 1 N weight of the piston, its movement stops. (ii) Pressure due to weight of piston = 1/(pi x 0.1^2) N/m^2 = 31.83 N/m^2 New pressure = (Po+31.83) N/m2 = 101,032 N/m2 where Po, atmospheric pressure = 1.01 x 10^5 N/m2 (Po).(63.65) = (Po+31.83).V', where V' is the new volume solve for V' gives V' = 63.63 cm^3 (iii) SInce it is an isothermal process, the P-V diagram follows an isothermal line.
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