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Thermal Properties of Matter — Physics STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 SciencePhysicsThermal Properties of Matter4 Marks
Question
Read the passage given below and answer the following questions from (i) to (v). A system is said to be isolated if no exchange or transfer of heat occurs between the system and its surroundings. When different parts of an isolated system are at different temperature a quantity of heat transfers from the part at higher temperature to the part at lower temperature. The heat lost by the part at higher temperature is equal to the heat gained by the part at lower temperature. Calorimetry means measurement of heat. When a body at higher temperature is brought in contact with another body at lower temperature, the heat lost by the hot body is equal to the heat gained by the colder body, provided no heat is allowed to escape to the surroundings. A device in which heat measurement can be done is called a calorimeter. It consists of a metallic vessel and stirrer of the same material, like copper or aluminium. The vessel is kept inside a wooden jacket, which contains heat insulating material. Matter normally exists in three states: solid, liquid and gas. A transition from one of these states to another is called a change of state. Two common changes of states are solid to liquid and liquid to gas (and, vice versa). These changes can occur when the exchange of heat takes place between the substance and its surroundings. The change of state from solid to liquid is called melting and from liquid to solid is called fusion. It is observed that the temperature remains constant until the entire amount of the solid substance melts. That is, both the solid and the liquid states of the substance coexist in thermal equilibrium during the change of states from solid to liquid. The temperature at which the solid and the liquid states of the substance is in thermal equilibrium with each other is called its melting point. The change of state from liquid to vapour (or gas) is called vaporisation. It is observed that the temperature remains constant until the entire amount of the liquid is converted into vapour. That is, both the liquid and vapour states of the substance coexist in thermal equilibrium, during the change of state from liquid to vapour. The temperature at which the liquid and the vapour states of the substance coexist is called its boiling point. The change from solid state to vapour state without passing through the liquid state is called sublimation, and the substance is said to sublime. Dry ice (solid $CO_2$) sublimes, so also iodine. During sublimation both the solid and vapour states of a substance coexist in thermal equilibrium.
  1. Device used for measurement of heat is:
  1. Calorimeter
  2. Thermometer
  3. Both a and b
  4. No one of these
  1. The change of state from solid to liquid is called:
  1. Melting
  2. Vaporization
  3. Sublimation
  4. None of these
  1. Define melting point and boiling point:
  2. What is sublimation?
  3. Define fusion process:
✓

Answer

  1. (a) Calorimeter.
  2. (a) Melting.
  3. The change of state from solid to liquid is called melting process and temperature at which conversion of solid into liquid happens is called as melting point. The temperature at which the liquid and the vapour states of the substance coexist is called its boiling point.
  4. The change from solid state directly into vapour state without passing through the liquid state is called sublimation, and the substance is said to sublime.
  5. The change of state from liquid state to solid state is called as fusion process.

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