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PHYSICS TEST, CHAPTER 7: THERMAL PROPERTIES OF MATTER, Time allowed: 1½ hour, Maximum Marks: 35 marks, Q.1. Select and write correct answer of the following questions. (05 marks), 1. What is the value of coefficient of volume expansion for an ideal gas?, a) (ΔV/V)/Δ T, b) 2 × coefficient of linear expansion, c) 1/3 × coefficient of linear expansion, d) (V/ΔV)/ Δ T, 2. A uniform metal sheet has a hole in its centre. What happens to hole when the sheet is uniformly heated?, a) Its size increases, b) Its size decreases, c) It changes shape, d) Remains the same size, 3. What is the principle of a calorimeter?, a) Heat loss rate is directly proportional to temperature difference, b) The total heat lost by a hot body is same as the total heat gained by the cold body provided no heat is lost to the surroundings, c) Heat loss depends only on specific heat of a substance, d) For the same amount of heat flow from a sample to two different samples of same mass is a product of their specific heats and temperature difference, 4. Why is water used in automobiles as a coolant?, a) It is not toxic for the environment, b) It has a high specific heat capacity, c) It has a high lubricating property which in turn keeps the engine cool by reducing friction, d) It is available in abundance, 5. Select the correct statement., a) Radiation doesn’t require any medium, b) Convection involves heat transfer by vibration of particles at their position, c) Conduction involves movement of particles to transfer heat, d) Radiation is responsible for heat of gas flame heating the cooking pan, Q.2. Answer the following questions. (10 marks), 1.Explain how behaviour of water is different than solids and liquids when heat is supplied., 2. Derive relation between coefficient of linear expansion (α) and coefficient of cubical expansion (γ)., 3. Explain why specific heat capacity of a gas at constant pressure is greater than that at constant volume., 4. Explain mechanism of thermal conduction and temperature gradient., 5. Distinguish between free convection and forced convection., Q.3. Define the following terms. (02 marks), 1. Calorimetry, 2. Coefficient of superficial (areal) expansion of a solid, Q.4. Solve the following numericals. (08 marks), 1. The length of a metal rod at 27 °C is 4 cm. The length increases to 4.02 cm when the metal rod is heated upto 387 °C. Determine the coefficient of linear expansion of the metal rod., 2. How much heat is required to raise temperature of 750 g of copper pot from 20 to 50 °C?, (The specific heat of copper is 0.094 kcal/kg °C), 3. A body cools at the rate of 0.5 °C/s when it is at 50 °C above the surrounding temperature. What is its rate of cooling when it is at 30 °C above the surrounding temperature?, 4. Heat is conducted through a copper plate at the rate of 460 cal/s-cm2. Calculate the temperature gradient when the steady state is reached. (kcopper = 92 cal/m-s °C), Q.5. Answer the following questions. (10 marks), 1. Compare conduction, convection and radiation., 2. Explain the technique “method of mixtures’., 3. Define principal and molar specific heat of a gas at constant volume and constant pressure., 4. Derive an expression for coefficient of cubical expansion., 5. Explain how SI unit of coefficient of thermal conductivity be obtained as W/m °C or W/m K.