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Doctors Medicines MCQs Q&A

  1. Only 1 is correct
  2. Only 2 & 3 is correct
  3. All are correct
  4. Only 1 & 2 is correct
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1 Answers

Option 3 : All are correct

The correct answer is 3 i.e. All are correct.

Latent heat :

  • The heat energy which has to be supplied to change the state of a substance is called its latent heat.
  • Latent heat does not raise the temperature.
  • But latent heat has always to be supplied to change the state of a substance. 
  • The word 'latent' means hidden.
  • The latent heat which we supply is used up in overcoming the forces of attraction between the particles of a substance during the change of state.
  • Latent heat is of two types:
    • Latent heat of fusion 
    • Latent heat of vaporization
      Phenomenon Explanation
      Latent heat of fusion 
      • There is no rise in temperature during the melting of ice.
      • The heat which is going into ice but not increasing its temperature is the energy required to change the state of ice from solid to liquid.
      • The heat energy is used up in changing the state of the solid substance by overcoming the force of attraction between its particles.
      • Ice at 0°C is more effective in cooling a substance than water at 0°C.
      • When a liquid freezes to form a solid, an equal amount of heat is given out.
      Latent heat of vaporization
      • Once the water has begun to boil, the temperature remains constant at 100°C until all the water has changed into steam.
      • The heat energy supplied to a boiling liquid is used up in changing the state of the liquid substance by overcoming the force of attraction between its particles.
      • When water changes into steam, it absorbs latent heat, but when steam condenses to form water, an equal amount of latent heat is given out.
      • The burns caused by steam are much more severe than those caused by boiling water.
      • This is because steam contains more heat, in the form of latent heat than boiling water.
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