Question 2
2
Question 2(a)
2(a)
Question 2(a)(i)
2(a)(i)
State what is meant by the internal energy of a system.
Answer
sum of kinetic and potential energies of the molecules M1 reference to random distribution A1
Question bank
A-Level CAIE Physics 16 1 Internal Energy Question Bank
Practice A-Level CAIE Physics 16 1 Internal Energy questions by syllabus topic with past-paper context, marks, difficulty and question previews on Eduninja.
Question 2
2
the rate h of thermal energy gained by the ice from the surroundings. W
Question 2(a)
2(a)
State what is meant by internal energy.
Answer
(sum of) potential energy and kinetic energy of molecules/atoms/particles \(\begin{array}{ll}\text { (sum of) potential energy and kinetic energy of molecules/atoms/particles } & \text { M1 } \\ \text { mention of random motion/distribution } & \text { A1 }\end{array}\)
Question 2
2
A cylinder contains 5.12 mol of an ideal gas at pressure \(5.60 \times 10^{5} \mathrm{~Pa}\) and volume \(3.80 \times 10^{-2} \mathrm{~m}^{3}\).
Question 2(b)
2(b)
The average kinetic energy \(E_{\mathrm{K}}\) of a molecule of the gas is given by the expression where k is the Boltzmann constant and T is the thermodynamic temperature. The gas is heated at constant pressure so that its temperature rises by 125 K .
Question 2(b)(ii)
2(b)(ii)
Calculate the increase in internal energy of the gas. Explain your working.
Answer
(for ideal gas,) change in internal energy is change in (total) kinetic energy (of molecules) B1 \(\Delta U=(3 / 2) \times 1.38 \times 10^{-23} \times 125 \times 5.12 \times 6.02 \times 10^{23}\) C1 \(\Delta U=7980 \mathrm{~J}\) A1
Question 2
2
the period of Deimos in its orbit about Mars. period = hours
Question 2(c)
2(c)
Question 2(c)(i)
2(c)(i)
State what is meant by the internal energy of a substance.
Answer
sum of potential energy and kinetic energy of molecules/atoms/particles reference to random (distribution)
Question 2
2
electric potential energy. energy = J
Question 2(c)
2(c)
Helium-4 may be assumed to behave as an ideal gas. A cylinder has a constant volume of \(7.8 \times 10^{3} \mathrm{~cm}^{3}\) and contains helium-4 gas at a pressure of \(2.1 \times 10^{7} \mathrm{~Pa}\) and at a temperature of 290 K . Calculate, for the helium gas,
Question 2(c)(iii)
2(c)(iii)
the total internal energy. internal energy = J
Answer
realisation that total internal energy is the total kinetic energy C1 energy \(=6.0 \times 10^{-21} \times 68 \times 6.02 \times 10^{23}\) C1 \(=2.46 \times 10^{5} \mathrm{~J} \quad\) A1
Question 2
2
A constant mass of an ideal gas has a volume of \(3.49 \times 10^{3} \mathrm{~cm}^{3}\) at a temperature of \(21.0^{\circ} \mathrm{C}\). When the gas is heated, 565 J of thermal energy causes it to expand to a volume of \(3.87 \times 10^{3} \mathrm{~cm}^{3}\) at \(53.0^{\circ} \mathrm{C}\). This is illustrated in Fig.2.1.
Question 2(c)
2(c)
Explain why the change in kinetic energy of the molecules of this ideal gas is equal to the change in internal energy.
Answer
internal energy = sum of kinetic energy and potential energy \(/ E_{\mathrm{K}}+E_{\mathrm{P}}\) no intermolecular forces no potential energy (so \(\Delta U=\Delta E_{\mathrm{K}}\) )
Question 2
2
A student suggests that, when an ideal gas is heated from \(100^{\circ} \mathrm{C}\) to \(200^{\circ} \mathrm{C}\), the internal energy of the gas is doubled.
Question 2(a)
2(a)
Question 2(a)(i)
2(a)(i)
State what is meant by internal energy.
Answer
sum of potential energy and kinetic energy of atoms/molecules/particles M1 reference to random
Question 2(b)
2(b)
State and explain whether the student's suggestion is correct.
Answer
kinetic energy \(\propto\) thermodynamic temperature either temperature in Celsius, not kelvin so incorrect or temperature in kelvin is not doubled
Question 2
2
Question 2(c)
2(c)
A negative temperature coefficient thermistor may be used as a type of resistance thermometer. State one way in which the variation with temperature of the resistance of a thermistor differs from that of a platinum wire.
Answer
(variation is) inverse or (variation is) non-linear B1
Question 2
2
Question 2(a)
2(a)
By referring to both kinetic energy and potential energy, explain what is meant by the internal energy of an ideal gas.
Answer
total kinetic energy associated with random motion of molecules M1 plus total potential energy (of molecules) but potential energy is zero A1
Question 2
2
air and soft tissue.
Question 2(a)
2(a)
Question 2(a)(ii)
2(a)(ii)
State what is meant by the internal energy of a substance.
Answer
sum of kinetic and potential energy of atoms / molecules M1 due to random motion A1
Question 2(a)(iii)
2(a)(iii)
Explain why an increase in internal energy of an ideal gas is directly related to a rise in temperature of the gas.
Answer
(random) kinetic energy increases with temperature M1 no potential energy (so increase in temperature increases internal energy) A1