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THERMAL PROPERTIES OF MATTER
Study Material
THERMAL PROPERTIES OF MATTER
Very Short Answer Questions
Q1. Distinguish between heat and temperature.
Q2. What are the lower and upper fixing points in Celsius and Fahrenheit scales?
Q3. Do the values of coefficients of expansion differ, whether the temperatures are measured on Centigrade scale or on Fahrenheit scale?
Q4. Can a substance contract on heating? Give an example.
Q5. Why do gaps are left between rails on a railway track?
Q6. Why do liquids have no linear and areal expansions?
Q7. What is latent heat of fusion?
Q8. What is latent heat of vaporization?
Q9. Why are utensils coated black? Why does the bottom of utensils made of copper?
Q10. State Wien's displacement law.
Q11. Define specific heat.
Q12. Does a body radiate heat at 0 K? Does it radiate heat at 0°C?
Q13. State the different modes of transmission of heat. Which of these modes require medium?
Q14. What is regelation of ice?
Q15. Define thermal expansion.
Q16. What is the principle of pressure cooker?
Q17. If the maximum intensity of radiation for a black body is found at \(2.65\,\mu\mathrm{m}\), what is the temperature of the radiating body? (Wien's constant \(=2.9\times10^{-3}\,\mathrm{m\,K}\))
Q18. State Newton's law of cooling.
Q19. State the conditions under which Newton's law of cooling is applicable.
Q20. The roof of buildings are often painted white during summer. Why?
Q1. Explain Celsius and Fahrenheit scales of temperature. Obtain the relation between Celsius and Fahrenheit scales of temperature.
Q2. Pendulum clocks generally go fast in winter and slow in summer. Why?
Q3. In what way is the anomalous behaviour of water advantageous to aquatic animals?
Q4. Explain conduction, convection and radiation with neat diagram.
Q1. Explain thermal conductivity and coefficient of thermal conductivity. A copper bar of thermal conductivity \(401\,\mathrm{W\,m^{-1}K^{-1}}\) has one end at \(104^\circ\mathrm{C}\) and the other end at \(24^\circ\mathrm{C}\), length of the bar is \(0.10\,\mathrm{m}\) and the cross-sectional area is \(1.9\times10^{-4}\,\mathrm{m^2}\). What is the rate of heat conduction along the bar?
Q2. State and explain Newton's law of cooling. State the conditions under which Newton's law of cooling is applicable. A body cools down from 60°C to 50°C in 5 minutes and to 40°C in another 8 minutes. Find the temperature of the surroundings.
Q1. What is the temperature for which the readings on Kelvin and Fahrenheit scales are same?
Q2. Find the increase in temperature of aluminium rod if its length is to be increased by \(1\%\). (\(\alpha\) for aluminium \(=25\times10^{-6}\,^\circ\mathrm{C}^{-1}\))
Q3. How much steam at \(100^\circ\mathrm{C}\) is to be passed into water of mass \(100\,\mathrm{g}\) at \(20^\circ\mathrm{C}\) to raise its temperature by \(5^\circ\mathrm{C}\)? (Latent heat of steam is \(540\,\mathrm{cal\,g^{-1}}\) and specific heat of water is \(1\,\mathrm{cal\,g^{-1}\,^\circ C^{-1}}\))
Q4. \(2\,\mathrm{kg}\) of air is heated at constant volume. The temperature of air is increased from \(293\,\mathrm{K}\) to \(313\,\mathrm{K}\). If the specific heat of air at constant volume is \(0.718\,\mathrm{kJ\,kg^{-1}K^{-1}}\), find the amount of heat absorbed in kJ and kcal. (\(J=4.2\,\mathrm{kJ/kcal}\))
Q5. A clock, with a brass pendulum, keeps correct time at \(20^\circ\mathrm{C}\), but loses \(8.212\,\mathrm{s}\) per day, when the temperature rises to \(30^\circ\mathrm{C}\). Calculate the coefficient of linear expansion of brass.
Q6. A body cools from \(60^\circ\mathrm{C}\) to \(40^\circ\mathrm{C}\) in \(7\) minutes. What will be its temperature after next \(7\) minutes if the temperature of its surroundings is \(10^\circ\mathrm{C}\)?
Q7. If the maximum intensity of radiation for a black body is found at \(2.65\,\mu\mathrm{m}\), what is the temperature of the radiating body? (Wien's constant \(=2.9\times10^{-3}\,\mathrm{m\,K}\))
Q8. What is the temperature for which the readings on Fahrenheit and Celsius scales are same?
Q1. Show that the coefficient of areal expansion, \(\beta\), of a rectangular sheet of the solid is twice its linear expansivity, \(\alpha\).
Q2. A blacksmith has to fit an iron ring on the rim of the wooden wheel of a bullock cart. The diameter of the rim and the iron ring are \(5.243\,\mathrm{m}\) and \(5.291\,\mathrm{m}\) respectively at \(27^\circ\mathrm{C}\). To what temperature should the ring be heated so that it fits the rim of the wheel? The coefficient of linear expansion of iron is \(1.2\times10^{-5}\,\mathrm{K^{-1}}\).
Q3. A sphere of aluminium of \(0.047\,\mathrm{kg}\) is kept for sufficient time in a vessel containing boiling water, so that the sphere is at \(100^\circ\mathrm{C}\). It is then immediately transferred to \(0.14\,\mathrm{kg}\) copper calorimeter containing \(0.25\,\mathrm{kg}\) water at \(20^\circ\mathrm{C}\). The temperature of water rises and attains a steady state at \(23^\circ\mathrm{C}\). Calculate the specific heat capacity of aluminium.
Q4. When \(0.15\,\mathrm{kg}\) of ice of \(0^\circ\mathrm{C}\) is mixed with \(0.30\,\mathrm{kg}\) of water at \(50^\circ\mathrm{C}\) in a container, the resulting temperature is \(6.7^\circ\mathrm{C}\). Calculate the heat of fusion of ice.
Q5. Calculate the heat required to convert \(3\,\mathrm{kg}\) of ice at \(-12^\circ\mathrm{C}\) kept in a calorimeter to steam at \(100^\circ\mathrm{C}\) at atmospheric pressure. Given specific heat capacity of ice \(=2100\,\mathrm{J\,kg^{-1}K^{-1}}\), specific heat capacity of water \(=4186\,\mathrm{J\,kg^{-1}K^{-1}}\), latent heat of fusion of ice \(=3.35\times10^5\,\mathrm{J\,kg^{-1}}\) and latent heat of steam \(=2.256\times10^6\,\mathrm{J\,kg^{-1}}\).
Q6. What is the temperature of the steel-copper junction in the steady state of the system shown in Fig. 11.15? Length of the steel rod \(=15.0\,\mathrm{cm}\), length of the copper rod \(=10.0\,\mathrm{cm}\), cross-sectional area of the steel rod is twice the cross-sectional area of the copper rod. Thermal conductivity of steel \(=50.2\,\mathrm{J\,s^{-1}m^{-1}K^{-1}}\) and of copper \(=385\,\mathrm{J\,s^{-1}m^{-1}K^{-1}}\). The temperature of the furnace is \(300^\circ\mathrm{C}\) and the temperature of the other end is \(0^\circ\mathrm{C}\).
Q7. An iron bar \((L_1=0.1\,\mathrm{m}, A_1=0.02\,\mathrm{m^2}, K_1=79\,\mathrm{W\,m^{-1}K^{-1}})\) and brass bar \((L_2=0.1\,\mathrm{m}, A_2=0.02\,\mathrm{m^2}, K_2=109\,\mathrm{W\,m^{-1}K^{-1}})\) are soldered end-to-end as shown in Fig. 11.16. The free ends of the iron bar and brass bar are maintained at \(373\,\mathrm{K}\) and \(273\,\mathrm{K}\) respectively. Obtain expressions for and hence compute (i) the temperature of the junction of the two bars, (ii) the equivalent thermal conductivity of the combined bar, and (iii) the rate of heat conduction through the combined bar.
Q8. Calculate the heat required to convert \(3\,\mathrm{kg}\) of ice at \(-12^\circ\mathrm{C}\) kept in a calorimeter to steam at \(100^\circ\mathrm{C}\) at atmospheric pressure. Given specific heat capacity of ice \(=2100\,\mathrm{J\,kg^{-1}K^{-1}}\), specific heat capacity of water \(=4186\,\mathrm{J\,kg^{-1}K^{-1}}\), latent heat of fusion of ice \(=3.35\times10^5\,\mathrm{J\,kg^{-1}}\) and latent heat of steam \(=2.256\times10^6\,\mathrm{J\,kg^{-1}}\).