Available Answers

1. 1.

   Tick the most appropriate answer.

   1. Molecules of a solid
      1. vibrate at their positions.
      2. move only when heated.
      3. move because they are loosely bound,
      4. do not move at all.
   2. The force of attraction between two similar types of molecules is called
      1. adhesion.
      2. cohesion.
      3. electrostatic force.
      4. conduction.
   3. The temperature at which a solid changes into its liquid state is called
      1. boiling point.
      2. freezing point.
      3. condensation point.
      4. melting point.
   4. How does the kinetic energy of a molecule in a substance change with a decrease in its temperature?
      1. It remains the same.
      2. It increases.
      3. It decreases.
      4. It becomes twice.
   5. The state of matter, in which the kinetic energy of the molecule is so small that they cannot overcome the intermolecular force of attraction between then, is
      1. solid.
      2. liquid.
      3. gas.
      4. plasma.
   6. In convection currents,
      1. hot molecules rise up.
      2. cold molecules sink down.
      3. molecules actually move from their place.
      4. all of these.
2. 2.

   Fill in the blanks.

   1. The force of attraction between molecules of a substance is called _____________.
   2. The intermolecular force of attraction between the molecules ___________ with increase in temperature.
   3. In solids, intermolecular spaces are very _____________.
   4. The molecules of a gas are ____________ packed.
   5. During melting of a solid, its ____________ remains constant.
   6. The process of water changing into its vapour at 50°C is called _____________.
3. 3.

   Write true or false. Correct the false statements.

   1. An atom is defined as the smallest unit of matter that has an independent existence and carries the physical and chemical properties of that matter.
   2. The intermolecular force of attraction increases when intermolecular space increases.
   3. If the molecules in a substance have very large kinetic energies, which can completely overcome the intermolecular force of attraction between them, then the substance is a liquid.
   4. When a gas is cooled, its molecules lose energy and slow down.
   5. The force of attraction between the molecules of water and that of glass is the force of cohesion.
   6. The process of change of state from gaseous state directly to solid state is called sublimation.
4. 4.

   Match the columns.

   1. Solid to liquid	a. least intermolecular spaces
   2. Liquid to gas	b. least intermolecular forces
   3. Solid	c. melting
   4. Gas	d. mode of heat transfer
   5. Conduction	e. evaporation

    

5. 5.

   Define Freezing point.